Tasimelteon, タシメルテオン

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ChemSpider 2D Image | Tasimelteon | C15H19NO2




609799-22-6 [RN]
Hetlioz [Trade name]
N-{[(1R,2R)-2-(2,3-Dihydro-1-benzofuran-4-yl)cyclopropyl]methyl}propanamide [ACD/IUPAC Name]
Propanamide, N-[[(1R,2R)-2-(2,3-dihydro-4-benzofuranyl)cyclopropyl]methyl]- [ACD/Index Name]

609799-22-6 cas, BMS-214778; VEC-162, ATC:N05CH03

  • Use:Treatment of sleep disorder; Melatonin receptor agonist
  • (1R,2R)-N-[2-(2,3-dihydrobenzofuran-4-yl)cyclopropylmethyl]propanamide
  • Formula:C15H19NO2, MW:245.3 g/mol
  • Hetlioz Vanda Pharmaceuticals, 2014

Approved fda 2014


Tasimelteon is a white to off-white crystalline powder, it is non hygroscopic, soluble in water across relevant pH values and freely soluble in alcohols, cyclohexane, and acetonitrile. Conducted in vivo studies demonstrate that tasimelteon is highly permeable substance. Photostability testing and testing on stress conditions demonstrated that the active substance degrades in light.

Tasimelteon exhibits stereoisomerism due to the presence of two chiral centres. Active substance is manufactured as a single, trans-1R,2R isomer. Enantiomeric purity is controlled routinely during manufacture of active substance intermediates by chiral HPLC/specific optical rotation and additionally controlled in the active substance. Stability data indicates tasimelteon is isomerically stable.

Polymorphism has been observed in polymorphic screening studies for tasimelteon and two forms have been identified. The thermodynamically more stable form has been chosen for development and the manufacturing process consistently yields active substance of single, desired polymorphic form. It was demonstrated that milling of the active substance does not affect polymorphic form. Polymorphism is additionally controlled in active substance release and shelf-life specifications using X-ray powder diffraction analysis.

Tasimelteon is synthesized in nine main steps using linear synthesis and using commercially available well-defined starting materials with acceptable specifications. Three intermediates are isolated for control of active substance quality including stereochemical control. The active substance is isolated by slow recrystallisation or precipitation of tasimelteon from an ethanol/water mixture which ensures the formation of desired polymorphic form. Up to two additional, optional recrystallisations may be performed for unmilled tasimelteon to ensure that milled tasimelteon active substance is of high purity. Seed crystals complying with active substance specifications can be used optionally. Active substance is jet milled (micronised) to reduce and control particle size, which is critical in finished product performance with regards to content uniformity and dissolution…….http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Public_assessment_report/human/003870/WC500190309.pdf

launched in 2014 in the U.S. by Vanda Pharmaceuticals for the treatment of non-24-hour sleep-wake disorder in totally blind subjects. In 2015, the European Committee for Medicinal Products of the European Medicines Agency granted approval for the same indication.  In 2010 and 2011, orphan drug designations were assigned for the treatment of non-24 hour sleep/wake disorder in blind individuals without light perception in the U.S. and the E.U., respectively.

Tasimelteon (trade name Hetlioz) is a drug approved by the U.S. Food and Drug Administration (FDA)[2] in January 2014 for the treatment of non-24-hour sleep–wake disorder (also called Non-24, N24 and N24HSWD).[3] In June 2014, the European Medicines Agency accepted an EU filing application for tasimelteon[4] and in July 2015, the drug was approved in Europe for the treatment of non-24-hour sleep-wake rhythm disorder in totally blind adults,[5] but not in the rarer case of non-24 in sighted people.

Tasimelteon is a selective agonist for the melatonin receptors MT1 and MT2, similar to other members of the melatonin receptor agonistclass of which ramelteon (2005) and agomelatine (2009) were the first approved.[6] As a treatment for N24HSWD, as with melatonin or other melatonin derivatives, the patient may experience improved sleep timing while taking the drug. Reversion to baseline sleep performance occurs within a month of discontinuation.[7]



Tasimelteon (previously known as BMS-214,778) was developed for the treatment of insomnia and other sleep disorders. A phase II trial on circadian rhythm sleep disorders was concluded in March 2005.[8] A phase III insomnia trial was conducted in 2006.[9] A second phase III trial on insomnia, this time concerning primary insomnia, was completed in June 2008.[10] In 2010, the FDA granted orphan drug status to tasimelteon, then regarded as an investigational medication, for use in totally blind adults with N24HSWD.[11] (Through mechanisms such as easing the approval process and extending exclusivity periods, orphan drug status encourages development of drugs for rare conditions that otherwise might lack sufficient commercial incentive.)

On completion of Phase III trials, interpretations of the clinical trials by the research team concluded that the drug may have therapeutic potential for transient insomnia in circadian rhythm sleep disorders.[12] A year-long (2011–2012) study at Harvard tested the use of tasimelteon in blind subjects with non-24-hour sleep-wake disorder. The drug has not been tested in children nor in any non-blind people.

FDA approval

In May 2013 Vanda Pharmaceuticals submitted a New Drug Application to the Food and Drug Administration for tasimelteon for the treatment of non-24-hour sleep–wake disorder in totally blind people. It was approved by the FDA on January 31, 2014 under the brand name Hetlioz.[3] In the opinion of Public Citizen, an advocacy group, the FDA erroneously allowed it to be labelled without stating that it is only approved for use by totally blind people.[13] However, FDA updated its press release on Oct. 2, 2014 to clarify the approved use of Hetlioz, which includes both sighted and blind individuals. The update did not change the drug labeling (prescribing information).[14]


Experiments with rodents revealed fertility impairments, an increase in certain cancers, and serious adverse events during pregnancy at dosages in excess of what is considered the “human dose”.[15][16]

As expected, advisors to the US Food and Drug Administration have recommended approval of Vanda Pharmaceuticals’ tasimelteon, to be sold as Hetlioz, for the treatment of non-24-hour disorder in the totally blind.http://www.pharmatimes.com/Article/13-11-14/FDA_panel_backs_Vanda_body_clock_drug_for_blind.aspx

The master body clock controls the timing of many aspects of physiology, behavior and metabolism that show daily rhythms, including the sleep-wake cycles, body temperature, alertness and performance, metabolic rhythms and certain hormones which exhibit circadian variation. Outputs from the

suprachiasmatic nucleus (SCN) control many endocrine rhythms including those of melatonin secretion by the pineal gland as well as the control of Cortisol secretion via effects on the hypothalamus, the pituitary and the adrenal glands. This master body clock, located in the SCN, spontaneously generates rhythms of approximately 24.5 hours. These non-24-hour rhythms are synchronized each day to the 24-hour day-night cycle by light, the primary environmental time cue which is detected by specialized cells in the retina and transmitted to the SCN via the retino-hypothalamic tract. Inability to detect this light signal, as occurs in most totally blind individuals, leads to the inability of the master body clock to be reset daily and maintain entrainment to a 24-hour day.

Non-24-Hour Disorder, Non-24, also referred to as Non-24-Hour Sleep-Wake Disorder, (N24HSWD) or Non-24-Hour Disorder, is an orphan indication affecting approximately 65,000 to 95,000 people in the U.S. and 140,000 in Europe. Non- 24 occurs when individuals, primarily blind with no light perception, are unable to synchronize their endogenous circadian pacemaker to the 24-hour light/dark cycle. Without light as a synchronizer, and because the period of the internal clock is typically a little longer than 24 hours, individuals with Non-24 experience their circadian drive to initiate sleep drifting later and later each day. Individuals with Non-24 have abnormal night sleep patterns, accompanied by difficulty staying awake during the day. Non-24 leads to significant impairment, with chronic effects impacting the social and occupational functioning of these individuals.

In addition to problems sleeping at the desired time, individuals with Non-24 experience excessive daytime sleepiness that often results in daytime napping.

The severity of nighttime sleep complaints and/or daytime sleepiness complaints varies depending on where in the cycle the individual’s body clock is with respect to their social, work, or sleep schedule. The “free running” of the clock results in approximately a 1-4 month repeating cycle, the circadian cycle, where the circadian drive to initiate sleep continually shifts a little each day (about 15 minutes on average) until the cycle repeats itself. Initially, when the circadian cycle becomes desynchronous with the 24h day-night cycle, individuals with Non-24 have difficulty initiating sleep. As time progresses, the internal circadian rhythms of these individuals becomes 180 degrees out of synchrony with the 24h day-night cycle, which gradually makes sleeping at night virtually impossible, and leads to extreme sleepiness during daytime hours.

Eventually, the individual’s sleep-wake cycle becomes aligned with the night, and “free-running” individuals are able to sleep well during a conventional or socially acceptable time. However, the alignment between the internal circadian rhythm and the 24-hour day-night cycle is only temporary.

In addition to cyclical nighttime sleep and daytime sleepiness problems, this condition can cause deleterious daily shifts in body temperature and hormone secretion, may cause metabolic disruption and is sometimes associated with depressive symptoms and mood disorders.

It is estimated that 50-75% of totally blind people in the United States (approximately 65,000 to 95,000) have Non-24. This condition can also affect sighted people. However, cases are rarely reported in this population, and the true rate of Non-24 in the general population is not known.

The ultimate treatment goal for individuals with Non-24 is to entrain or synchronize their circadian rhythms into an appropriate phase relationship with the 24-hour day so that they will have increased sleepiness during the night and increased wakefulness during the daytime. Tasimelteon

Tasimelteon is a circadian regulator which binds specifically to two high affinity melatonin receptors, Mella (MT1R) and Mellb (MT2R). These receptors are found in high density in the suprachiasmatic nucleus of the brain (SCN), which is responsible for synchronizing our sleep/wake cycle. Tasimelteon has been shown to improve sleep parameters in prior clinical studies, which simulated a desynchronization of the circadian clock. Tasimelteon has so far been studied in hundreds of individuals and has shown a good tolerability profile.

Tasimelteon has the chemical name: tr ns-N-[[2-(2,3-dihydrobenzofuran- 4-yl)cycloprop-lyl] methyl] propanamide, has the structure of Formula I:

Figure imgf000008_0001

Formula I

and is disclosed in US 5856529 and in US 20090105333, both of which are incorporated herein by reference as though fully set forth.

Tasimelteon is a white to off-white powder with a melting point of about 78°C (DSC) and is very soluble or freely soluble in 95% ethanol, methanol, acetonitrile, ethyl acetate, isopropanol, polyethylene glycols (PEG-300 and PEG- 400), and only slightly soluble in water. The native pH of a saturated solution of tasimelteon in water is 8.5 and its aqueous solubility is practically unaffected by pH. Tasimelteon has 2-4 times greater affinity for MT2R relative to MTIR. It’s affinity (¾) for MTIR is 0.3 to 0.4 and for MT2R, 0.1 to 0.2. Tasimelteon is useful in the practice of this invention because it is a melatonin agonist that has been demonstrated, among other activities, to entrain patients suffering from Non-24.

Metabolites of tasimelteon include, for example, those described in “Preclinical Pharmacokinetics and Metabolism of BMS-214778, a Novel

Melatonin Receptor Agonist” by Vachharajani et al., J. Pharmaceutical Sci., 92(4):760-772, which is hereby incorporated herein by reference. The active metabolites of tasimelteon can also be used in the method of this invention, as can pharmaceutically acceptable salts of tasimelteon or of its active metabolites. For example, in addition to metabolites of Formula II and III, above, metabolites of tasimelteon also include the monohydroxylated analogs M13 of Formula IV, M12 of Formula V, and M14 of Formula VI.

Formula IV

Figure imgf000010_0001

Formula V


Figure imgf000010_0002

Formula VI

Thus, it is apparent that this invention contemplates entrainment of patients suffering free running circadian rhythm to a 24 hour circadian rhythm by administration of a circadian rhythm regulator (i.e., circadian rhythm modifier) capable of phase advancing and/or entraining circadian rhythms, such as a melatonin agonist like tasimelteon or an active metabolite oftasimelteon or a pharmaceutically acceptable salt thereof. Other MT1R and MT2R agonists, i.e., melatonin agonists, can have similar effects on the master body clock. So, for example, this invention further contemplates the use of melatonin agonists such as but not limited to melatonin, N-[l-(2,3-dihydrobenzofuran-4- yl)pyrrolidin-3-yl]-N-ethylurea and structurally related compounds as disclosed in US 6,211,225, LY-156735 ((R)-N-(2-(6-chloro-5-methoxy-lH-indol- 3yl) propyl) acetamide) (disclosed in U.S. Patent No. 4,997,845), agomelatine (N- [2-(7-methoxy-l-naphthyl)ethyl]acetamide) (disclosed in U.S. Patent No.

5,225,442), ramelteon ((S)-N-[2-(l,6,7,8-tetrahydro-2H-indeno- [5,4-b] furan-8- yl)ethyl]propionamide), 2-phenylmelatonin, 8-M-PDOT, 2-iodomelatonin, and 6- chloromelatonin.

Additional melatonin agonists include, without limitation, those listed in U.S. Patent Application Publication No. 20050164987, which is incorporated herein by reference, specifically: TAK-375 (see Kato, K. et al. Int. J.

Neuropsychopharmacol. 2000, 3 (Suppl. 1): Abst P.03.130; see also abstracts P.03.125 and P.03.127), CGP 52608 (l-(3-allyl-4-oxothiazolidine-2-ylidene)-4- met- hylthiosemicarbazone) (See Missbach et al., J. Biol. Chem. 1996, 271, 13515-22), GR196429 (N-[2-[2,3,7,8-tetrahydro-lH-fur-o(2,3-g)indol-l- yl] ethyl] acetamide) (see Beresford et al., J. Pharmacol. Exp. Ther. 1998, 285, 1239-1245), S20242 (N-[2-(7-methoxy napth-l-yl) ethyl] propionamide) (see Depres-Brummer et al., Eur. J. Pharmacol. 1998, 347, 57-66), S-23478 (see Neuropharmacology July 2000), S24268 (see Naunyn Schmiedebergs Arch. June 2003), S25150 (see Naunyn Schmiedebergs Arch. June 2003), GW-290569, luzindole (2-benzyl-N-acetyltryptamine) (see U.S. Patent No. 5,093,352), GR135531 (5-methoxycarbonylamino-N-acetyltrypt- amine) (see U.S. Patent Application Publication No. 20010047016), Melatonin Research Compound A, Melatonin Agonist A (see IMSWorld R&D Focus August 2002), Melatonin

Analogue B (see Pharmaprojects August 1998), Melatonin Agonist C (see Chem. Pharm. Bull. (Tokyo) January 2002), Melatonin Agonist D (see J. Pineal Research November 2000), Melatonin Agonist E (see Chem. Pharm. Bull. (Tokyo) Febrary 2002), Melatonin Agonist F (see Reprod. Nutr. Dev. May 1999), Melatonin Agonist G (see J. Med. Chem. October 1993), Melatonin Agonist H (see Famaco March 2000), Melatonin Agonist I (see J. Med. Chem. March 2000), Melatonin Analog J (see Bioorg. Med. Chem. Lett. March 2003), Melatonin Analog K (see MedAd News September 2001), Melatonin Analog L, AH-001 (2-acetamido-8- methoxytetralin) (see U.S. Patent No. 5,151,446), GG-012 (4-methoxy-2- (methylene propylamide)indan) (see Drijfhout et al., Eur. J. Pharmacol. 1999, 382, 157-66), Enol-3-IPA, ML-23 (N-2,4-dinitrophenyl-5-methoxy-tryptamine ) (see U.S. Patent No. 4,880,826), SL-18.1616, IP-100-9 (US 5580878), Sleep Inducing Peptide A, AH-017 (see U.S. Patent No. 5,151,446), AH-002 (8-methoxy- 2-propionamido-tetralin) (see U.S. Patent No. 5,151,446), and IP-101.

Metabolites, prodrugs, stereoisomers, polymorphs, hydrates, solvates, and salts of the above compounds that are directly or indirectly active can, of course, also be used in the practice of this invention.

Melatonin agonists with a MT1R and MT2R binding profile similar to that of tasimelteon, which has 2 to 4 time greater specificity for MT2R, are preferred.

Tasimelteon can be synthesized by procedures known in the art. The preparation of a 4-vinyl-2,3-dihydrobenzofuran cyclopropyl intermediate can be carried out as described in US7754902, which is incorporated herein by reference as though fully set forth.

Pro-drugs, e.g., esters, and pharmaceutically acceptable salts can be prepared by exercise of routine skill in the art.

In patients suffering a Non-24, the melatonin and Cortisol circadian rhythms and the natural day/night cycle become desynchronized. For example, in patients suffering from a free-running circadian rhythm, melatonin and Cortisol acrophases occur more than 24 hours, e.g., >24.1 hours, prior to each previous day’s melatonin and Cortisol acrophase, respectively, resulting in desynchronization for days, weeks, or even months, depending upon the length of a patient’s circadian rhythm, before the melatonin, Cortisol, and day /night cycles are again temporarily synchronized.

Chronic misalignment of Cortisol has been associated with metabolic, cardiac, cognitive, neurologic, neoplastic, and hormonal disorders. Such disorders include, e.g., obesity, depression, neurological impairments.

Structure-activity relationship
Figure : Melatonin receptor agonists. The applied colors indicate the mutual properties with the general melatonin receptor agonists pharmacophore.


Tasimelteon has the chemical name: trans-N-[[2-(2,3-dihydrobenzofuran-4-yl)cycloprop-1yl]methyl]propanamide, has the structure of Formula I:

Figure US20130197076A1-20130801-C00001

and is disclosed in U.S. Pat. No. 5,856,529 and in US 20090105333, both of which are incorporated herein by reference as though fully set forth.

Tasimelteon is a white to off-white powder with a melting point of about 78° C. (DSC) and is very soluble or freely soluble in 95% ethanol, methanol, acetonitrile, ethyl acetate, isopropanol, polyethylene glycols (PEG-300 and PEG-400), and only slightly soluble in water. The native pH of a saturated solution of tasimelteon in water is 8.5 and its aqueous solubility is practically unaffected by pH. Tasimelteon has 2-4 times greater affinity for MT2R relative to MT1R. It’s affinity (Ki) for MT1R is 0.3 to 0.4 and for MT2R, 0.1 to 0.2. Tasimelteon is useful in the practice of this invention because it is a melatonin agonist that has been demonstrated, among other activities, to entrain patients suffering from Non-24.



(1R-trans)-N-[[2 – (2,3-dihydro-4 benzofuranyl) cyclopropyl] methyl] propanamide PATENT: BRISTOL-MYERS SQUIBB PRIORITY DATE: 1996 HYPNOTIC

Synthesis Tasimelteon



…………XXV (1S, 4R) -7,7-dimethyl-2-oxo-bicyclo [2.2.1] heptane-1-methanesulfonyl chloride


XXVI ammonium hydroxide


XXVII (1S, 4R) -7,7-dimethyl-2-oxo-bicyclo [2.2.1] heptane-1-methanesulfonamide


….XXVIII (3aS, 6R) -4,5,6,7-tetrahydro-8 ,8-dimethyl-3H-3a ,6-methano-2 ,1-benzisothiazole-2 ,2-dioxide

TREATED WITH LAH, ie double bond is reduced to get

…..XV (3aS, 6R, 7aR)-hexahydro-8 ,8-dimethyl-3H-3a ,6-methano-2 ,1-benzisothiazole-2 ,2-dioxide


I 3-hydroxybenzoic acid methyl ester

II 3-bromo-1-propene

III 3 – (2-propenyloxy) benzoic acid methyl ester

IV 3-hydroxy-2-(2-propenyl) benzoic acid methyl ester

V 2,3-dihydro-4-hydroxy-2-benzofurancarboxylic acid methyl ester

VI benzofuran-4-carboxylic acid methyl ester

VII benzofuran-4-carboxylic acid

VIII 2,3-dihydro-4-benzofurancarboxylic acid

IX 2,3-dihydro-4-benzofuranmethanol

X 2,3-dihydro-4-benzofurancarboxaldehyde

XI Propanedioic acid

XII (E) -3 – (2,3-dihydro-4-benzofuranyl) propenoic acid

XIII thionyl chloride

XIV (E) -3 – (2,3-dihydro-4-benzofuranyl) propenoyl chloride

XV (3aS, 6R, 7aR)-hexahydro-8 ,8-dimethyl-3H-3a ,6-methano-2 ,1-benzisothiazole-2 ,2-dioxide

XVI (3aS,6R,7aR)-1-[(E)-3-(2,3-dihydro-4-benzofuranyl)-1-oxo-2-propenyl]hexahydro-8,8-dimethyl-3H-3a,6-methano-2,1-benzisothiazole-2,2-dioxide

XVII (3aS,6R,7aR)-1-[[(1R,2R)-2-(2,3-dihydro-4-benzofuranyl)cyclopropyl]carbonyl]hexahydro-8,8-dimethyl-3H-3a,6-methano-2,1-benzisothiazole-2,2-dioxide

XVIII [R-(R *, R *)] -2 – (2,3-dihydro-4-benzofuranyl) cyclopropanemethanol

XIX [R-(R *, R *)] -2 – (2,3-dihydro-4-benzofuranyl) cyclopropanecarboxaldehyde

XX hydroxylamine hydrochloride

XXI [R-(R *, R *)] -2 – (2,3-dihydro-4-benzofuranyl) cyclopropanecarbaldehyde oxime

XXII [R-(R *, R *)] -2 – (2,3-dihydro-4-benzofuranyl) cyclopropanemethanamine

XXIII propanoyl chloride

XXIV D-camphorsulfonic acid

XXV (1S, 4R) -7,7-dimethyl-2-oxo-bicyclo [2.2.1] heptane-1-methanesulfonyl chloride

XXVI ammonium hydroxide

XXVII (1S, 4R) -7,7-dimethyl-2-oxo-bicyclo [2.2.1] heptane-1-methanesulfonamide

XXVIII (3aS, 6R) -4,5,6,7-tetrahydro-8 ,8-dimethyl-3H-3a ,6-methano-2 ,1-benzisothiazole-2 ,2-dioxide


– Patents: Benzofuran and dihydrobenzofuran melatonergic agents: US5856529 (1999)

Priority: US19960032689P, 10 Dec. 1996 (Bristol-Myers Squibb Company, U.S.)

– Preparation III (quinazolines): US2004044015 (2004) Priority: EP20000402845, 13 Oct. 2000

– Preparation of VII (aminoalkylindols): Structure-Activity Relationships of Novel Cannabinoid Mimetics Eissenstat et al, J.. Med. Chem. 1995, 38, 3094-3105

– Preparation XXVIII: Towson et al. Organic Syntheses, Coll. Vol. 8, p.104 (1993) Vol. 69, p.158 (1990)

– Preparation XV: Weismiller et al. Organic Syntheses, Coll. Vol. 8, p.110 (1993) Vol. 69, p.154 (1990).

– G. Birznieks et al. Melatonin agonist VEC-162 Improves sleep onset and maintenance in a model of transient insomnia. Sleep 2007, 30, 0773 Abstract.

-. Rajaratnam SM et al, The melatonin agonist VEC-162 Phase time immediately advances the human circadian system, Sleep 2006, 29, 0159 Abstract.

-. AK Singh et al, Evolution of a manufacturing route for a highly potent drug candidate, 229th ACS Natl Meet, March 13-17, 2005, San Diego, Abstract MEDI 576.

– Vachharajani NN et al, Preclinical pharmacokinetics and metabolism of BMS-214778, a novel melatonin receptor agonist, J Pharm Sci. 2003 Apr; 92 (4) :760-72.

. – JW Scott et al, Catalytic Asymmetric Synthesis of a melotonin antagonist; synthesis and process optimization. 223rd ACS Natl Meet, April 7-11, Orlando, 2002, Abstract ORGN 186.





Reaction Scheme 1

Figure imgf000020_0001

The syntheses of the 4-aryl-propenoic acid derivatives, 2 and 3, are shown in Reaction Scheme 1. The starting aldehydes, 1 , can be prepared by methods well known to those skilled in the art. Condensation of malonic acid with the aldehydes, 1, in solvents such as pyridine with catalysts such as piperidine or pyrrolidine, gives the 4-aryl- propenoic acid, 2. Subsequent conversion of the acid to the acid chloride using reagents such as thionyl chloride, phosphoryl chloride, or the like, followed by reaction with N,0-dimethyl hydroxylamine gives the amide intermediate 3 in good yields. Alternatively, aldehyde 1 can be converted directly to amide 3 using reagents such as diethyl (N-methoxy- N-methyl-carbamoylmethyl)phosphonate with a strong base such as sodium hydride.

Reaction Scheme 2

Figure imgf000020_0002

The conversion of the amide intermediate 3 to the racemic, trans- cyclopropane carboxaldehyde intermediate, 4, is shown in Reaction Scheme 2. Intermediate 3 was allowed to react with cyclopropanating reagents such as trimethylsulfoxonium iodide and sodium hydride in solvents such as DMF, THF, or the like. Subsequent reduction using reagents such as LAH in solvents such as THF, ethyl ether, or the like, gives the racemic, trans-cyclopropane carboxaldehyde intermediates, 4.

Reaction Scheme 3

Figure imgf000021_0001

Racemic cyclopropane intermediate 5 (R = halogen) can be prepared from intermediate 2 as shown in Reaction Scheme 3. Intermediate 2 was converted to the corresponding allylic alcohol by treatment with reducing agents such as sodium borohydride plus iodine in solvents such as THF. Subsequent acylation using reagents such as acetic anhydride in pyridine or acetyl chloride gave the allylic acetate which was allowed to react with cyclopropanating reagents such as sodium chloro-difluoroacetate in diglyme to provide the racemic, trans- cyclopropane acetate intermediates, 5. Reaction Scheme 4

Figure imgf000022_0001

The conversion of the acid 2 to the chiral cyclopropane carboxaldehyde intermediate, (-)-(trans)-4, is shown in Reaction Scheme 4. Intermediate 2 is condensed with (-)-2,10-camphorsultam under standard conditions, and then cyclopropanated in the presence of catalysts such as palladium acetate using diazomethane generated from reagents such as 1-methyl-3-nitro-1-nitrosoguanidine. Subsequent reduction using reagents such as LAH in solvents such as THF, followed by oxidation of the alcohol intermediates using reagents such as DMSO/oxalyl chloride, or PCC, gives the cyclopropane carboxaldehyde intermediate, (-)-(trans)-4, in good yields. The enantiomer, (+)-(trans)-4, can also be obtained employing a similar procedure using (+)-2,10- camphorsultam in place of (-)-2,10-camphorsultam.

When it is desired to prepare compounds of Formula I wherein m = 2, the alcohol intermediate may be activated in the conventional manner such as with mesyl chloride and treated with sodium cyanide followed by reduction of the nitrile group with a reducing agent such as LAH to produce the amine intermediate 6.

Reaction Scheme 5

Figure imgf000023_0001
Figure imgf000023_0002

Reaction Scheme 5 shows the conversion of intermediates 4 and 5 to the amine intermediate, 7, and the subsequent conversion of 6. or 7 to compounds of Formula I. The carboxaldehyde intermediate, 4, is condensed with hydroxylamine and then reduced with reagents such as LAH to give the amine intermediate, 7. The acetate intermediate 5 is hydrolyzed with potassium hydroxide to the alcohol, converted to the mesylate with methane sulfonyl chloride and triethyl amine in CH2CI2and then converted to the azide by treatment with sodium azide in solvents such as DMF. Subsequent reduction of the azide group with a reducing agent such as LAH produced the amine intermediate 7. Further reaction of 6 or 7 with acylating reagents gives compounds of Formula I. Suitable acylating agents include carboxylic acid halides, anhydrides, acyl imidazoles, alkyl isocyanates, alkyl isothiocyanates, and carboxylic acids in the presence of condensing agents, such as carbonyl imidazole, carbodiimides, and the like. Reaction Scheme 6

Figure imgf000024_0001

Reaction Scheme 6 shows the alkylation of secondary amides of Formula I (R2 = H) to give tertiary amides of Formula I (R2 = alkyl). The secondary amide is reacted with a base such as sodium hydride, potassium tert-butoxide, or the like, and then reacted with an alkylating reagent such as alkyl halides, alkyl sulfonate esters, or the like to produce tertiary amides of Formula I.

Reaction Scheme 7

Figure imgf000024_0002

Reaction Scheme 7 shows the halogenation of compounds of Formula I. The carboxamides, i (Q1 = Q2 = H), are reacted with excess amounts of halogenating agents such as iodine, N-bromosuccinimide, or the like to give the dihalo-compounds of Formula I (Q1 = Q2 = halogen). Alternatively, a stoichiometric amount of these halogenating agents can be used to give the monohalo-compounds of Formula I (Q1 = H, Q2 = halogen; or Q1 = halogen, Q2 = H). In both cases, additives such as lead IV tetraacetate can be used to facilitate the reaction. Biological Activity of the Compounds

The compounds of the invention are melatonergic agents. They have been found to bind human melatonergic receptors expressed in a stable cell line with good affinity. Further, the compounds are agonists as determined by their ability, like melatonin, to block the forskolin- stimulated accumulation of cAMP in certain cells. Due to these properties, the compounds and compositions of the invention should be useful as sedatives, chronobiotic agents, anxiolytics, antipsychotics, analgesics, and the like. Specifically, these agents should find use in the treatment of stress, sleep disorders, seasonal depression, appetite regulation, shifts in circadian cycles, melancholia, benign prostatic hyperplasia and related conditions



Preparation 1


Step 1 : N-Methoxy-N-methyl-benzofuran-4-carboxamide

A mixture of benzofuran-4-carboxylic acid [Eissenstat, et al.. J. Medicinal Chemistry, 38 (16) 3094-3105 (1995)] (2.8 g, 17.4 mmol) and thionyl chloride (25 mL) was heated to reflux for 2 h and then concentrated in vacuo. The solid residue was dissolved in ethyl acetate (50 mL) and a solution of N,O-dimethylhydroxylamine hydrochloride (2.8 g) in saturated NaHC03(60 mL) was added with stirring. After stirring for 1.5 h, the ethyl acetate layer was separated. The aqueous layer was extracted with ethyl acetate. The ethyl acetate extracts were combined, washed with saturated NaHCO3 and concentrated in vacuo to give an oil (3.2 g, 95.4%).

Step 2: Benzofuran-4-carboxaldehyde

A solution of N-methoxy-N-methyl-benzofuran-4-carboxamide (3.2 g, 16.6 mmol) in THF (100 mL) was cooled to -45°C and then LAH (0.7 g, 18.7 mmol) was added. The mixture was stirred for 15 min, allowed to warm to -5°C, and then recooled to -45°C. Saturated KHS04 (25 mL) was added with vigorous stirring, and the mixture was allowed to warm to room temperature. The precipitate was filtered and washed with acetone. The filtrate was concentrated in vacuo to give an oil (2.3 g, 94%). Preparation 2


Step 1 : 2,3-Dihydrobenzofuran-4-carboxylic acid

Benzofuran-4-carboxylic acid (10.0 g, 61 .7 mmol) was hydrogenated (60 psi) in acetic acid (100 mL) over 10% Pd/C (2 g) for 12 hr. The mixture was filtered and the filtrate was diluted with water (500 mL) to give 2,3- dihydrobenzofuran-4-carboxylic acid as a white powder (8.4 g, 83%). A sample was recrystallized from isopropanol to give fine white needles (mp: 185.5-187.5°C).

Step 2: (2,3-Dihydrobenzofuran-4-yl)methanol

A solution of 2,3-dihydrobenzofuran-4-carboxylic acid (10 g, 61 mmol) in THF (100 mL) was stirred as LAH (4.64 g, 122 mmol) was slowly added. The mixture was heated to reflux for 30 min. The mixture was cooled and quenched cautiously with ethyl acetate and then with 1 N HCI (150 mL). The mixture was then made acidic with 12 N HCI until all the inorganic precipitate dissolved. The organic layer was separated, and the inorganic layer was extracted twice with ethyl acetate. The organic layers were combined, washed twice with brine, and then concentrated in vacuo. This oil was Kϋgelrohr distilled to a clear oil that crystallized upon cooling (8.53 g, 87.6%).

Step 3: 2.3-Dihydrobenzofuran-4-carboxaldehyde

DMSO (8.10 mL, 1 14 mmol) was added at -78°C to a stirred solution of oxalyl chloride in CH2CI2 (40 mL of a 2M solution). A solution of (2,3- dihydrobenzofuran-4-yl)methanol (8.53 g, 56.9 mmol) in CH2CI2 (35 mL) was added dropwise, and the solution stirred at -78°C for 30 min. Triethyl amine (33 mL, 228 mmol) was added cautiously to quench the reaction. The resulting suspension was stirred at room temperature for 30 min and diluted with CH2CI2 (100 mL). The organic layer was washed three times with water, and twice with brine, and then concentrated in vacuo to an oil (8.42 g, 100%) that was used without purification.

Preparation 16

(±)-(trans)-2-(2,3-Dihyd robenzofuran-4-yl)cyclopropane- carboxaldehyde

Step 1 : (±Htrans)-N-Methoxy-N-methyl-2-(2.3-dihydrobenzofuran-4- yhcyclopropanecarboxamide

Trimethylsulfoxonium iodide (9.9 g, 45 mmol) was added in small portions to a suspension of sodium hydride (1 .8 g, 45 mmol) in DMF (120 mL). After the foaming had subsided (10 min), a solution of (trans)- N-methoxy-N-methyl-3-(2,3-dihydrobenzofuran-4-yl)propenamide (3.5 g, 15 mmol) in DMF (60 mL) was added dropwise, with the temperature maintained between 35-40°C. The mixture was stirred for 3 h at room temperature. Saturated NH4CI (50 mL) was added dropwise and the mixture was extracted three times with ethyl acetate. The organic extracts were combined, washed with H2O and brine, dried over K2CO3, and concentrated in vacuo to give a white wax (3.7 g, 100%).

Step 2: (±)-(trans)- 2-(2.3-Dihydrobenzofuran-4-yl)cyclopropane- carboxaldehyde

A solution of (±)-(trans)-N-methoxy-N-methyl-2-(2,3-dihydrobenzofuran- 4-yl)cyclopropanecarboxamide (3.7 g, 15 mmol) in THF (10 mL) was added dropwise to a rapidly stirred suspension of LAH (683 mg, 18 mmol) in THF (50 mL) at -45°C, maintaining the temperature below -40°C throughout. The cooling bath was removed, the reaction was allowed to warm to 5°C, and then the reaction was immediately recooled to -45°C. Potassium hydrogen sulfate (3.4 g, 25.5 mmol) in H20 (50 mL) was cautiously added dropwise, the temperature maintained below – 30°C throughout. The cooling bath was removed and the suspension was stirred at room temperature for 30 min. The mixture was filtered through Celite and the filter cake was washed with ether. The combined filtrates were then washed with cold 1 N HCI, 1 N NaOH, and brine. The filtrates were dried over MgSO4, and concentrated in vacuo to give a clear oil (2.6 g, 99%).

Preparation 18


Step 1 : (-Htrans)-N-[3-(2.3-Dihvdrobenzofuran-4-yl)-propenoyll-2.10- camphorsultam

To a solution of (-)-2,10-camphorsultam (8.15 g, 37.9 mmol) in 50 mL toluene at 0°C was added sodium hydride (1.67 g, 41.7 mmol). After stirring for 0.33 h at 0°C and 0.5 h at 20°C and recooling to 0°C, a solution of 3-(2,3-dihydrobenzofuran-4-yl)-2-propenoyl chloride
(37.9 mmol), prepared in situ from the corresponding acid and thionyl chloride (75 mL), in toluene (50 mL), was added dropwise. After stirring for 18 h at 20°C, the mixture was diluted with ethyl acetate and washed with water, 1 N HCI, and 1 N NaOH. The organic solution was dried and concentrated in vacuo to give 15.8 g of crude product. Recrystallization form ethanol-methanol (600 mL, 1 :1) gave the product (13.5 g, 92%, mp 199.5-200°C).

Step 2: (-)-N-[[(trans)-2-(2,3-Dihydrobenzofuran-4-yl)-cyclopropylj- carbonylj-2, 10-camphorsultam

1 -Methyl-3-nitro-1 -nitrosoguanidine (23.88g 163 mmol) was added in portions to a mixture of 10 N sodium hydroxide (60 mL) and ether (200 mL) at 0°C. The mixture was shaken vigorously for 0.25 h and the ether layer carefully decanted into a solution of (-)-N-[3-(2,3-dihydrobenzofuran-4-yl)-2-propenoyl]-2,10-camphorsultam (9.67 g, 25 mmol) and palladium acetate (35 mg) in methylene chloride (200 mL). After stirring for 18 h, acetic acid (5 mL) was added to the reaction and the mixture stirred for 0.5 h. The mixture was washed with 1 N HCI, 1 N NaOH and brine. The solution was dried, concentrated in vacuo and the residue crystallized twice from ethanol to give the product (6.67 g, 66.5%, mp 157-159°C).

Step 3: (-)-(trans)-2-(2,3-Dihydrobenzofuran-4-yl)cyclopropane- methanol

A solution of (-)-N-[(trans)-2-(2,3-dihydrobenzofuran-4-yl)cyclo-propanecarbonylj-2,10-camphorsultam (4.3 g, 10.7 mmol) in THF (50 mL) was added dropwise to a mixture of LAH (0.81 g, 21.4 mmol) in THF (50 mL) at -45°C. The mixture was stirred for 2 hr while it warmed to 10°C. The mixture was recooled to -40°C and hydrolyzed by the addition of saturated KHS0 (20 mL). The mixture was stirred at room temperature for 30 minutes and filtered. The precipitate was washed twice with acetone. The combined filtrate and acetone washes were concentrated in vacuo. The gummy residue was dissolved in ether, washed with 1 N NaOH and 1 N HCI, and then dried in vacuo to give the product (2.0 g, 98.4%).

Step 4: (-)-(trans)-2-(2.3-Dihydrobenzofuran-4-yl)cyclopropane- carboxaldehyde DMSO (1.6 g, 21 mmol) was added to oxalyl chloride in CH2CI2(7.4 mL of 2 M solution, 14.8 mmole) at -78°C. The (-)-(trans)-2-(2,3-dihydrobenzofuran-4-yl)-cyclopropylmethanol (2.0 g, 10.5 mmol) in CH2CI2(15 mL) was added. The mixture was stirred for 20 min and then triethylamine (4.24 g, 42 mmol) was added. The mixture was warmed to room temperature and stirred for 30 min. The mixture was diluted with CH2CI2 and washed with water, 1 N HCI, and then 1 N NaOH. The organic layer was dried and concentrated iι> vacuo to give the aldehyde product (1.98 g, 100%).

Preparation 24

(-)-(trans)-2-(2.3-Dihydrobenzofuran-4-yl)cyclopropane-methanamine A mixture of (-)-(trans)-2-(2,3-dihydrobenzofuran-4-yl)cyclopropane-carboxaldehyde (1.98 g, 10.5 mmol), hydroxylamine hydrochloride (2.29 g, 33 mmol), and 30% NaOH (3.5 mL, 35 mmol), in 5:1
ethanol/water (50 mL) was heated on a steam bath for 2 h. The solution was concentrated in vacuo. and the residue mixed with water. The mixture was extracted with CH2CI2. The organic extracts were dried and concentrated in vacuo to give a solid which NMR analysis showed to be a mixture of the cis and trans oximes. This material was dissolved in THF (20 mL) and added to solution of alane in THF [prepared from LAH (1.14 g, 30 mmol) and H2S04 (1.47 g, 15 mmol) at 0°Cj. The reaction was stirred for 18 h, and quenched successively with water (1.15 mL), 15% NaOH (1.15 mL), and then water (3.45 mL). The mixture was filtered and the filtrate was concentrated in vacuo. The residue was mixed with ether and washed with water and then 1 N HCI. The acid washes were made basic and extracted with CH2CI . The extracts were dried and concentrated in vacuo to give the amine product (1.4 g, 70.5%). The amine was converted to the fumarate salt in ethanol (mp: 197-198°C).
Anal. Calc’d for C12H15NO • C4H404: C, 62.94; H, 6.27; N, 4.59.
Found: C, 62.87; H, 6.31 ; N, 4.52.


Example 2


This compound was prepared similar to the above procedure using propionyl chloride and (-)-(trans)-2-(2,3-dihydrobenzofuran-4-yl)- cyclopropanemethanamine to give an oil that solidified upon standing to an off-white solid (61 %, mp: 71-72°C). IR (NaCI Film): 3298, 1645, 1548, 1459, 1235 cm“1.

Mo5 : -17.3°

Anal. Calc’d for C15H19N02: C, 73.44; H, 7.87; N, 5.71 . Found: C, 73.28; H, 7.68; N, 5.58


Synthesis Path



Tasimelteon (Hetlioz)Tasimelteon, which is marketed by Vanda Pharmaceuticals as Hetlioz and developed in partnership with Bristol-Myers Squibb,is a drug that was approved by the US FDA in January 2014 for the treatment of non-24-hour sleep–wake disorder (also called Non-24, N24 and N24HSWD).234 Tasimelteon is a melatonin MT1
and MT2 receptor agonist; because it exhibits a greater affinity to the MT2 receptor than MT1, is also known as Dual Melatonin
Receptor Agonist.234 Two randomized controlled trials (phases II
and III) demonstrated that tasimelteon improved sleep latency
and maintenance of sleep with a shift in circadian rhythms, and
therefore has the potential to treat patients with transient insomnia
associated with circadian rhythm sleep disorders.235 Preclinical
studies showed that the drug has similar phase-shifting properties
to melatonin, but with less vasoconstrictive effects.236 The most
likely scale preparation of the drug, much of which has been published
in the chemical literature, is described below in Scheme 44.
Activation of commercial bis-ethanol 250 with 2.5 equivalents
of the Vilsmeier salt 251 followed by treatment with base resulted
an intramolecular cyclization reaction with the proximal phenol
and concomitant elimination of the remaining imidate to deliver
the vinylated dihydrobenzofuran 252 in 76% yield.237 Interestingly,
this reaction could be performed on multi-kilogram scale, required
no chromatographic purification, and generated environmentallyfriendly
DMF and HCl as byproducts.237 Sharpless asymmetric
dihydroxylation of olefin 252 delivered diol 253 in 86% yield and
impressive enantioselectivity (>99% ee). This diol was then activated
with trimethylsilyl chloride and then treated with base to generate epoxide 254.238 Next, a modified Horner–Wadsworth–
Emmons reaction involving triethylphosphonoacetate (TEPA, 255)
was employed to convert epoxide 254 to cyclopropane 256.239
The reaction presumably proceeds through removal of the acidic
TEPA proton followed by nucleophilic attack at the terminal epoxide
carbon. The resulting alkoxide undergoes an intramolecular
phosphoryl transfer reaction resulting in an enolate, which then attacked the newly formed phosphonate ester in an SN2 fashion
resulting in the trans-cyclopropane ester, which was ultimately
saponified and re-acidified to furnish cyclopropane acid 256.239
Conversion of this acid to the corresponding primary amide preceded
carbonyl reduction with sodium borohydride. The resulting
amine was acylated with propionyl chloride to furnish tasimelteon
(XXXI) as the final product in 86% yield across the four-step


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extra info

Org. Synth.199069, 154
[3H-3a,6-Methano-2,1-benzisothiazole, 4,5,6,7-tetrahydro-8,8-dimethyl-2,2-dioxide, (3aS)-]
Submitted by Michael C. Weismiller, James C. Towson, and Franklin A. Davis1.
Checked by David I. Magee and Robert K. Boeckman, Jr..
1. Procedure
(−)-2,10-Camphorsultam. A dry, 2-L, three-necked, round-bottomed flask is equipped with a 1.5-in egg-shaped Teflon stirring bar, a 250-mL addition funnel, and a 300-mL Soxhlet extraction apparatus equipped with a mineral oil bubbler connected to an inert-gas source. The flask is charged with 600 mL of dry tetrahydrofuran (THF) (Note 1) and6.2 g (0.16 mol) of lithium aluminum hydride (Note 2). Into the 50-mL Soxhlet extraction thimble is placed 35.0 g (0.16 mol) of (−)-(camphorsulfonyl)imine (Note 3) and the reaction mixture is stirred and heated at reflux. After all of the(camphorsulfonyl)imine has been siphoned into the reaction flask (3–4 hr), the mixture is allowed to cool to room temperature. The unreacted lithium aluminum hydride is cautiously hydrolyzed by dropwise addition of 200 mL of 1 Nhydrochloric acid via the addition funnel (Note 4). After the hydrolysis is complete the contents of the flask are transferred to a 1-L separatory funnel, the lower, silver-colored aqueous layer is separated, and the upper layer placed in a 1-L Erlenmeyer flask. The aqueous phase is returned to the separatory funnel and washed with methylene chloride (3 × 100 mL). After the reaction flask is rinsed with methylene chloride (50 mL), the organic washings are combined with the THF phase and dried over anhydrous magnesium sulfate for 10–15 min. Filtration through a 300-mL sintered-glass funnel of coarse porosity into a 1-L round-bottomed flask followed by removal of the solvent on arotary evaporator gives 33.5 g (95%) of the crude (−)-2,10-camphorsultam. The crude sultam is placed in a 250-mL Erlenmeyer flask and crystallized from approximately 60 mL of absolute ethanol. The product is collected on a 150-mL sintered-glass funnel of coarse porosity and dried in a vacuum desiccator to give 31.1 g (88%) of the pure sultam. A second crop of crystals can be gained by evaporating approximately half the filtrate; the residue is crystallized as above to give 1.4 g (4%). The combined yield of white crystalline solid, mp 183–184°C, [α]D −30.7° (CHCl3, c 2.3) is92% (Note 5) and (Note 6).
2. Notes
1. Tetrahydrofuran (Aldrich Chemical Company, Inc.) was distilled from sodium benzophenone.
2. Lithium aluminum hydride was purchased from Aldrich Chemical Company, Inc.
3. (−)-(Camphorsulfonyl)imine, [(7S)-(−)-10,10-dimethyl-5-thia-4-azatricyclo[,7]dec-3-ene 5,5-dioxide] was prepared by the procedure of Towson, Weismiller, Lal, Sheppard, and Davis, Org. Synth., Coll. Vol. VIII1993, 104.
4. The addition must be very slow at first (1 drop/5 sec) until the vigorous reaction has subsided.
5. The NMR spectrum of (−)-2,10-camphorsultam is as follows: 1H NMR (CDCl3) δ: 0.94 (s, 3 H, CH3), 1.14 (s, 3 H, CH3), 1.33 (m, 1 H), 1.47 (m,, 1 H), 1.80–2.05 (5 H), 3.09 (d, 1 H, J = 14), 3.14 (d, 1 H, J = 14), 3.43 (m, 1 H), 4.05 (br s, 1 H, NH); 13C NMR (CDCl3) δ: 20.17 (q, CH3), 26.51 (t), 31.55 (t), 35.72 (t), 44.44 (d), 47.15 (s), 50.08 (t), 54.46 (s), 62.48 (d).
6. Checkers obtained material having the same mp (183–184°C) and [α]D − 31.8° (CHCl3c 2.3).
3. Discussion
(−)-2,10-Camphorsultam was first prepared by the catalytic hydrogenation of (−)-(camphorsulfonyl)imine overRaney nickel.2 Lithium aluminum hydride reduction was used by Oppolzer and co-workers in their synthesis of the sultam.3,4 However, because of the low solubility of the sultam in tetrahydrofuran, a large amount of solvent was required.4 In the procedure described here the amount of solvent is significantly reduced by using a Soxhlet extractor to convey the imine slowly into the reducing medium.5
Oppolzer’s chiral auxiliary,6 (−)-2,10-camphorsultam, is useful in the asymmetric Diels–Alder reaction,3,4 and for the preparation of enantiomerically pure β-substituted carboxylic acids7 and diols,8 in the stereoselective synthesis of Δ2-isoxazolines,9 and in the preparation of N-fluoro-(−)-2,10-camphorsultam, an enantioselective fluorinating reagent.10

References and Notes
  1. Department of Chemistry, Drexel University, Philadelphia, PA 19104.
  2. Shriner, R. L.; Shotton, J. A.; Sutherland, H. J. Am. Chem. Soc.193860, 2794.
  3. Oppolzer, W.; Chapuis, C.; Bernardinelli, G. Helv. Chim. Acta198467, 1397.
  4. Vandewalle, M.; Van der Eycken, J.; Oppolzer, W.; Vullioud, C. Tetrahedron198642, 4035.
  5. Davis, F. A.; Towson, J. C.; Weismiller, M. C.; Lal, G.; Carroll,, P. J. J. Am. Chem. Soc.1988110, 8477.
  6. Oppolzer, W. Tetrahedron198743, 1969.
  7. Oppolzer, W.; Mills, R. J.; Pachinger, W.; Stevenson, T. Helv. Chim. Acta198669, 1542; Oppolzer, W.; Schneider, P. Helv. Chim. Acta198669, 1817; Oppolzer, W.; Mills, R. J.; Réglier, M. Tetrahedron Lett.198627, 183; Oppolzer, W.; Poli. G.Tetrahedron Lett.198627, 4717; Oppolzer, W.; Poli, G.; Starkemann, C.; Bernardinelli, G. Tetrahedron Lett.198829, 3559.
  8. Oppolzer, W.; Barras, J-P. Helv. Chim. Acta198770, 1666.
  9. Curran, D. P.; Kim, B. H.; Daugherty, J.; Heffner, T. A. Tetrahedron Lett.198829, 3555.
  10. Differding, E.; Lang, R. W. Tetrahedron Lett.198829, 6087.

Org. Synth.199069, 158
[4H-4A,7-Methanooxazirino[3,2-i][2,1]benzisothiazole, tetrahydro-9,9-dimethyl-, 3,3-dioxide, [4aS-(4aα,7α,8aR*)]]
Submitted by James C. Towson, Michael C. Weismiller, G. Sankar Lal, Aurelia C. Sheppard, Anil Kumar, and Franklin A. Davis1.
Checked by David I. Magee and Robert K. Boeckman, Jr..
1. Procedure
A. (+)-(1S)-10-Camphorsulfonamide. Into a 2-L, two-necked, round-bottomed flask, equipped with a 250-mL dropping funnel, a magnetic stirring bar, and a reflux condenser fitted with an outlet connected to a disposable pipettedipped in 2 mL of chloroform in a test tube for monitoring gas evolution, were placed 116 g (0.5 mol) ofcamphorsulfonic acid (Note 1) and 750 mL of reagent-grade chloroform. The suspension of camphorsulfonic acid was heated to reflux and 71.4 g (43.77 mL, 0.6 mol, 1.2 equiv) of freshly distilled thionyl chloride was added dropwise over a 1-hr period. Heating was continued until gas evolution (sulfur dioxide and hydrogen chloride) had ceased (approximately 9–10 hr). The resultant solution of camphorsulfonyl chloride in chloroform was converted tocamphorsulfonamide without further purification.
In a 5-L, two-necked, round-bottomed flask fitted with a 250-mL dropping funnel and a mechanical stirrer was placed a solution of 1.6 L of reagent-grade ammonium hydroxide solution and the flask was cooled to 0°C in an ice bath. The solution of the crude camphorsulfonyl chloride, prepared in the preceding section, was added dropwise to the ammonium hydroxide solution at 0–10°C over a period of 1 hr. The reaction mixture was warmed to room temperature, stirred for 4 hr, the organic layer separated, and the aqueous layer was extracted with methylene chloride (3 × 250 mL). The combined organic layers were washed with brine (250 mL) and dried over anhydrousmagnesium sulfate. Removal of the solvent on the rotary evaporator gave 104.0 g (90%) of the crudecamphorsulfonamide (Note 2) and (Note 3).
B. (−)-(Camphorsulfonyl)imine. A 1-L, round-bottomed flask is equipped with a 2-in. egg-shaped magnetic stirring bar, a Dean–Stark water separator, and a double-walled condenser containing a mineral oil bubbler connected to an inert gas source. Into the flask are placed 5 g of Amberlyst 15 ion-exchange resin (Note 4) and 41.5 g of the crude(+)-(1S)-camphorsulfonamide in 500 mL of toluene. The reaction mixture is heated at reflux for 4 hr. After the reaction flask is cooled, but while it is still warm (40–50°C), 200 mL of methylene chloride is slowly added to dissolve any(camphorsulfonyl)imine that crystallizes. The solution is filtered through a 150-mL sintered glass funnel of coarse porosity an the reaction flask and filter funnel are washed with an additional 75 mL of methylene chloride.
Isolation of the (−)-(camphorsulfonyl)imine is accomplished by removal of the toluene on the rotary evaporator. The resulting solid is recrystallized from absolute ethanol (750 mL) to give white crystals, 34.5–36.4 g (90–95%), mp225–228°C; [α]D −32.7° (CHCl3, c 1.9) (Note 5).
C. (+)-(2R, 8aS)-10-Camphorylsulfonyloxaziridine. A 5-L, three-necked, round-bottomed Morton flask is equipped with an efficient mechanical stirrer, a 125-mm Teflon stirring blade, a Safe Lab stirring bearing (Note 6), and a 500-mL addition funnel. Into the flask are placed the toluene solution of (−)-(camphorsulfonyl)imine (39.9 g, 0.187 mol)prepared in Step B and a room-temperature solution of 543 g (3.93 mol, 7 equiv based on oxone) of anhydrouspotassium carbonate dissolved in 750 mL of water. The reaction mixture is stirred vigorously and a solution of 345 g (0.56 mol, 6 equiv of KHSO5) of oxone dissolved in 1250 mL of water is added dropwise in three portions over 45 min(Note 7) and (Note 8). Completion of the oxidation is determined by TLC (Note 9) and the reaction mixture is filtered through a 150-mL sintered-glass funnel of coarse porosity to remove solids. The filtrate is transferred to a 3-L separatory funnel, the toluene phase is separated and the aqueous phase is washed with methylene chloride (3 × 100 mL). The filtered solids and any solids remaining in the Morton flask are washed with an additional 200 mL of methylene chloride. The organic extracts are combined and washed with 100 mL of saturated sodium sulfite, dried over anhydrousmagnesium sulfate for 15–20 min, filtered, and concentrated on the rotary evaporator. The resulting white solid is crystallized from approximately 500 mL of hot 2-propanol to afford, after drying under vacuum in a desiccator, 35.9 g(84%) of white needles, mp 165–167°C, [α]D +44.6° (CHCl3, c 2.2) (Note 10) and (Note 11).
(−)-(2S,8aR)-10-(camphorylsulfonyl)oxaziridine is prepared in a similar manner starting from (−)-10-camphorsulfonic acid; mp 166–167°C, [α]D +43.6° (CHCl3, c 2.2).
2. Notes
1. (1S)-(+)-10-Camphorsulfonic acid was purchased from Aldrich Chemical Company, Inc.
2. The crude sulfonamide is contaminated with 5–10% of the (camphorsulfonyl)imine, the yield of which increases on standing.
3. The 1H NMR spectrum of (+)-(1S)-10-camphorsulfonamide is as follows: (CDCl3) δ: 0.93 (s, 3 H, CH3), 1.07 (s, 3 H, CH3), 1.40–2.50 (m, 7 H), 3.14 and 3.53 (AB quartet, 2 H, CH2-SO2J = 15.1), 5.54 (br s, 2 H, NH2).
4. Amberlyst 15 ion-exchange resin is a strongly acidic, macroreticular resin purchased from Aldrich Chemical Company, Inc.
5. The spectral properties of (−)-(camphorsulfonyl)imine are as follows: 1H NMR (CDCl3) δ: 1.03 (s, 3 H, CH3), 1.18 (s, 3 H, CH3), 1.45–2.18 (m, 6 H), 2.65 (m, 1 H), 3.10 and 3.28 (AB quartet, 2 H, CH2-SO2J = 14.0); 13C NMR (CDCl3) δ: 19.01 (q, CH3), 19.45 (q, CH3), 26.64 (t), 28.44 (t), 35.92 (t), 44.64 (d), 48.00 (s), 49.46 (t), 64.52 (s), 195.52 (s); IR (CHCl3) cm−1: 3030, 2967, 1366. Checkers obtained material having identical melting point and [α]D−32.3° (CHCl3, c 1.8).
6. The SafeLab Teflon bearing can be purchased from Aldrich Chemical Company, Inc. A glass stirring bearing lubricated with silicone grease is unsatisfactory because the dissolved salts solidify in the shaft, causing freezing.
7. Efficient stirring is important and indicated by a milky white appearance of the solution.
8. Occasionally batches of oxone purchased from Aldrich Chemical Company, Inc., have exhibited reduced reactivity in this oxidation. Oxone exposed to moisture prior to use also gives reduced reactivity in this oxidation. If this occurs, oxone is added until oxidation is complete as determined by TLC (Note 9). Potassium carbonate is added as needed to maintain the pH at approximately 9.0. Oxone stored in the refrigerator under an inert atmosphere has shown no loss in reactivity for up to 6 months.
9. Oxidation is generally complete after addition of the oxone solution. The oxidation is monitored by TLC as follows. Remove approximately 0.5 mL of the toluene solution from the nonstirring solution, spot a 250-μm TLC silica gel plate, elute with methylene chloride, and develop with 10% molybdophosphoric acid in ethanol and heating(camphorsulfonyl)imine Rf = 0.28 and (camphorylsulfonyl)oxaziridine Rf = 0.62. If (camphorsulfonyl)imine is detected, stirring is continued at room temperature until the reaction is complete (see (Note 8)). If the reaction mixture takes on a brownish color after addition of oxone and has not gone to completion after 30 min, the reaction mixture is filtered through a 150-mL sintered-glass funnel of coarse porosity, and the solids are washed with 50 mL of methylene chloride. The aqueous/organic extracts are returned to the 5-L Morton flask and stirred vigorously and 52 g (0.08 mol, 1 equiv KHSO5) of oxone is added over 5 min and stirring continued until oxidation is complete (approximately 10–15 min).
10. The submitters employed a toluene solution of crude imine prepared in Part B and obtained somewhat higher yields (90–95%). However, the checkers obtained yields in this range on one half the scale using isolatedsulfonylimine.
11. The spectral properties of (+)-(camphorsulfonyl)oxaziridine are as follows: 1H NMR (CDCl3) δ: 1.03 (s, 3 H, CH3), 1.18 (s, 3 H, CH3), 1.45–2.18 (m, 6 H), 2.65 (d, 1 H), 3.10 and 3.28 (AB quartet, 2 H, CH2-SO2J = 14.0); 13C NMR (CDCl3) δ: 19.45 (q, CH3), 20.42 (q, CH3), 26.55 (t), 28.39 (t), 33.64 (t), 45.78 (d), 48.16 (s), 48.32 (t), 54.07 (s), 98.76 (s). The checkers obtained material (mp 165–167°C) having [α]D +44.7° (CHCl3, c 2.2).
3. Discussion
Camphorsulfonamide, required for the preparation of the (camphorsulfonyl)imine, was previously prepared in two steps. The first step involved conversion of camphorsulfonic acid to the sulfonyl chloride with PCl5 or SOCl2. The isolated sulfonyl chloride was converted in a second step to the sulfonamide by reaction with ammonium hydroxide. This modified procedure is more efficient because it transforms camphorsulfonic acid directly to camphorsulfonamide, avoiding isolation of the camphorsulfonyl chloride.
(Camphorsulfonyl)imine has been reported as a by-product of reactions involving the camphorsulfonamide.2,3,4,5Reychler in 1898 isolated two isomeric camphorsulfonamides,2 one of which was shown to be the(camphorsulfonyl)imine by Armstrong and Lowry in 1902.3 Vandewalle, Van der Eycken, Oppolzer, and Vullioud described the preparation of (camphorsulfonyl)imine in 74% overall yield from 0.42 mol of the camphorsulfonyl chloride.6 The advantage of the procedure described here is that, by using ammonium hydroxide, the camphorsulfonyl chloride is converted to the sulfonamide in >95% yield.7 The sulfonamide is of sufficient purity that it can be used directly in the cyclization step, which, under acidic conditions, is quantitative in less than 4 hr. These modifications result in production of the (camphorsulfonyl)imine in 86% overall yield from the sulfonyl chloride.
In addition to the synthesis of enantiomerically pure (camphorylsulfonyl)oxaziridine7 and its derivatives,8 the(camphorsulfonyl)imine has been used in the preparation of (−)-2,10-camphorsultam (Oppolzers’ auxiliary),6,9 (+)-(3-oxocamphorysulfonyl) oxaziridine,10 and the N-fluoro-2,10-camphorsultam, an enantioselective fluorinating reagent.11
The N-sulfonyloxaziridines are an important class of selective, aprotic oxidizing reagents.121314 Enantiomerically pure N-sulfonyloxaziridines have been used in the asymmetric oxidation of sulfides to sulfoxides (30–91% ee),15selenides to selenoxides (8–9% ee).16 disulfides to thiosulfinates (2–13% ee),5 and in the asymmetric epoxidation of alkenes (19–65% ee).17,18 Oxidation of optically active sulfonimines (R*SO2N=CHAr) affords mixtures of N-sulfonyloxaziridine diastereoisomers requiring separation by crystallization and/or chromatography.3
(+)-(Camphorylsulfonyl)oxaziridine described here is prepared in four steps from inexpensive (1S)-(+)- or (1R)-(+)-10-camphorsulfonic acid in 77% overall yield.7 Separation of the oxaziridine diastereoisomers is not required because oxidation is sterically blocked from the exo face of the C-N double bond in the (camphorsulfonyl)imine. In general, (camphorsulfonyl)oxaziridine exhibits reduced reactivity compared to other N-sulfonyloxaziridines. For example, while sulfides are asymmetrically oxidized to sulfoxides (3–77% ee), this oxaziridine does not react with amines or alkenes.7 However, this oxaziridine is the reagent of choice for the hydroxylation of lithium and Grignard reagents to give alcohols and phenols because yields are good to excellent and side reactions are minimized.19 This reagent has also been used for the stereoselective oxidation of vinyllithiums to enolates.20
The most important synthetic application of the (camphorylsulfonyl)oxaziridines is the asymmetric oxidation of enolates to optically active α-hydroxy carbonyl compounds.14,21,22,23,24 Chiral, nonracemic α-hydroxy carbonylcompounds have been used extensively in asymmetric synthesis, for example, as chiral synthons, chiral auxiliaries, and chiral ligands. This structural array is also featured in many biologically active natural products. This oxidizing reagent gives uniformly high chemical yields regardless of the counterion, and stereoselectivities are good to excellent (50–95% ee).9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24 Since the configuration of the oxaziridine three-membered ring controls the stereochemistry, both α-hydroxy carbonyl optical isomers are readily available. Representative examples of the asymmetric oxidation of prochiral enolates by (+)-(2R,8aS)-camphorylsulfonyl)oxaziridine are given in Tables I and II.

This preparation is referenced from:

  • Org. Syn. Coll. Vol. 8, 110
  • Org. Syn. Coll. Vol. 9, 212
  • References and Notes
    1. Department of Chemistry, Drexel University, Philadelphia, PA 19104.
    2. Reychler, M. A. Bull. Soc. Chim. III188919, 120.
    3. Armstrong, H. E.; Lowry, T. M. J. Chem. Soc., Trans.190281, 1441.
    4. Dauphin, G.; Kergomard, A.; Scarset, A. Bull. Soc. Chim. Fr.1976, 862.
    5. Davis, F. A.; Jenkins, Jr., R. H.; Awad, S. B.; Stringer, O. D.; Watson, W. H.; Galloy, J. J. Am. Chem. Soc.1982104, 5412.
    6. Vandewalle, M.; Van der Eycken, J.; Oppolzer, W.; Vullioud, C. Tetrahedron198642, 4035.
    7. Davis, F. A.; Towson, J. C.; Weismiller, M. C.; Lal, S.; Carroll, P. J. J. Am. Chem. Soc.1988110, 8477.
    8. Davis, F. A.; Weismiller, M. C.; Lal, G. S.; Chen, B. C.; Przeslawski, R. M. Tetrahedron Lett.198930, 1613.
    9. Oppolzer, W. Tetrahedron198743, 1969.
    10. Glahsl, G.; Herrmann, R. J. Chem. Soc., Perkin Trans. I1988, 1753.
    11. Differding, E.; Lang, R. W. Tetrahedron Lett.198829, 6087.
    12. For recent reviews on the chemistry of N-sulfonyloxaziridines, see: (a) Davis, F. A.; Jenkins, Jr., R. H. in “Asymmetric Synthesis,” Morrison, J. D., Ed.; Academic Press: Orlando, FL, 1984, Vol. 4, Chapter 4;
    13. Davis, F. A.; Haque, S. M. in “Advances in Oxygenated Processes,” Baumstark, A. L., Ed.; JAI Press: London, Vol. 2;
    14. Davis, F. A.; Sheppard, A. C. Tetrahedron198945, 5703.
    15. Davis, F. A.; McCauley, Jr., J. P.; Chattopadhyay, S.; Harakal, M. E.; Towson, J. C.; Watson, W. H.; Tavanaiepour, I. J. Am. Chem. Soc.1987109, 3370.
    16. Davis, F. A.; Stringer, O. D.; McCauley, Jr., J. M. Tetrahedron198541, 4747.
    17. Davis, F. A.; Chattopadhyay, S. Tetrahedron Lett.198627, 5079.
    18. Davis, F. A.; Harakal, M. E.; Awad, S. B. J. Am. Chem. Soc.1983105, 3123.
    19. Davis, F. A.; Wei, J.; Sheppard, A. C.; Gubernick S. Tetrahedron Lett.198728, 5115.
    20. Davis, F. A.; Lal, G. S.; Wei, J. Tetrahedron Lett.198829, 4269.
    21. Davis, F. A.; Haque, M. S.; Ulatowski, T. G.; Towson, J. C. J. Org. Chem.198651, 2402.
    22. Davis, F. A.; Haque, M. S. J. Org. Chem.198651, 4083; Davis, F. A.; Haque, M. S.; Przeslawski, R. M. J. Org. Chem.198954, 2021.
    23. Davis, F. A.; Ulatowski, T. G.; Haque, M. S. J. Org. Chem.198752, 5288.
    24. Davis, F. A.; Sheppard, A. C., Lal, G. S. Tetrahedron Lett.198930, 779.
    25. Davis, F. A.; Sheppard, A. C.; Chen, B. C.; Haque, M. S. J. Am. Chem. Soc.1990112, 6679.

a US 5 856 529 (Bristol-Myers Squibb; 5.1.1999; appl. 9.12.1997; USA-prior. 10.12.1996).

    • b US 7 754 902 (Vanda Pharms.; 13.7.2010; appl. 18.5.2006).
  • treatment of circadian rhythm disorders:

    • US 8 785 492 (Vanda Pharms.; 22.7.2014; appl. 25.1.2013; USA-prior. 26.1.2012).
  • synthesis cis-isomer:

    • US 6 214 869 (Bristol-Myers Squibb; 10.4.2001; appl. 25.5.1999; USA-prior. 5.6.1998).


  1. USUS5856529 A
  2. USUS8785492 B2
  3. US5856529
  4. US8785492
  5. US9060995
  6. US9549913
  7. US9539234
  8. US9730910
  9. USRE46604
  10. US9855241


  1. Jump up^ “Tasimelteon Advisory Committee Meeting Briefing Materials”(PDF). Vanda Pharmaceuticals Inc. November 2013.
  2. Jump up^ “FDA transcript approval minutes” (PDF). FDA. November 14, 2013.
  3. Jump up to:a b Food and Drug Administration (January 31, 2014). “FDA approves Hetlioz: first treatment for non-24 hour sleep-wake disorder”. FDA.
  4. Jump up^ “tasimelteon (Hetlioz) UKMi New Drugs Online Database”. Retrieved August 6, 2014.
  5. Jump up^ “HETLIOZ® Receives European Commission Approval for the Treatment of Non-24-Hour Sleep-Wake Disorder in the Totally Blind”MarketWatch. PR Newswire. 7 July 2015. Retrieved 8 July 2015.
  6. Jump up^ Vachharajani, Nimish N.; Yeleswaram, Krishnaswamy; Boulton, David W. (April 2003). “Preclinical pharmacokinetics and metabolism of BMS-214778, a novel melatonin receptor agonist”. Journal of Pharmaceutical Sciences92 (4): 760–72. doi:10.1002/jps.10348PMID 12661062.
  7. Jump up^ Sack, R. L.; Brandes, R. W.; Kendall, A. R.; Lewy, A. J. (2000). “Entrainment of Free-Running Circadian Rhythms by Melatonin in Blind People”. New England Journal of Medicine343 (15): 1070–7. doi:10.1056/NEJM200010123431503PMID 11027741.
  8. Jump up^ “Safety and Efficacy of VEC-162 on Circadian Rhythm in Healthy Adult Volunteers”. ClinicalTrials.gov. |accessdate=May 15, 2014
  9. Jump up^ “VEC-162 Study in Healthy Adult Volunteers in a Model of Insomnia”. ClinicalTrials.gov. Retrieved May 15, 2014.
  10. Jump up^ “VEC-162 Study in Adult Patients With Primary Insomnia”. ClinicalTrials.gov. Retrieved May 15, 2014.
  11. Jump up^ Lynne Lamberg. “Improving Sleep and Alertness in the Blind (Part 5)”Matilda Ziegler Magazine for the Blind. Retrieved May 15, 2014.
  12. Jump up^ Shantha MW Rajaratnam; Mihael H Polymeropoulos; Dennis M Fisher; Thomas Roth; Christin Scott; Gunther Birznieks; Elizabeth B Klerman (2009-02-07). “Melatonin agonist tasimelteon (VEC-162) for transient insomnia after sleep-time shift: two randomised controlled multicentre trials”The Lancet373 (9662): 482–491. doi:10.1016/S0140-6736(08)61812-7PMID 19054552. Retrieved 2010-02-23.
  13. Jump up^ Carome, Michael (1 July 2015). “Outrage of the Month: FDA Makes Major Blunder After Approving Drug for Rare Sleep Disorder”Huffington Post. Retrieved 8 July 2015.
  14. Jump up^ Food and Drug Administration (January 31, 2014). “FDA NEWS RELEASE: FDA approves Hetlioz: first treatment for non-24 hour sleep–wake disorder in blind individuals”. FDA.
  15. Jump up^ “Side Effects Drug Center: Hetlioz Clinical Pharmacology”. RxList. February 10, 2014.
  16. Jump up^ “Side Effects Drug Center: Hetlioz Warnings and Precautions”. RxList. February 10, 2014. In animal studies, administration of tasimelteon during pregnancy resulted in developmental toxicity (embryofetal mortality, neurobehavioral impairment, and decreased growth and development in offspring) at doses greater than those used clinically.
Tasimelteon 2.svg
Tasimelteon ball-and-stick model.png
Clinical data
Trade names Hetlioz
License data
  • US:C (Risk not ruled out)
Routes of
ATC code
Legal status
Legal status
Pharmacokinetic data
Bioavailability not determined in humans[1]
Protein binding 89–90%
Metabolism extensive hepatic, primarily CYP1A2 and CYP3A4-mediated
Elimination half-life 0.9–1.7 h / 0.8–5.9 h (terminal)
Excretion 80% in urine, 4% in feces
CAS Number
ECHA InfoCard 100.114.889Edit this at Wikidata
Chemical and physical data
Formula C15H19NO2
Molar mass 245.32 g/mol
3D model (JSmol)




MOBILE-+91 9323115463


//////////////BMS-214778, VEC-162, Tasimelteon, Hetlioz, FDA 2014, 609799-22-6 , BMS-214778, VEC-162, ATC N05CH03, タシメルテオン , EU 2015, VANDA, BMS, orphan drug designations

Chemical and physical properties 

Tasimelteon has two stereogenic centers. Besides the medically used trans-1 R , 2 R isomer (in the picture above left), there are thus three further stereoisomers that do not arise in the synthesis.

Tasimelteon stereoisomerism.svg

Tasimelteon is a white to off-white crystalline non-hygroscopic substance, soluble in water at physiologically relevant pH levels and readily soluble in alcohols, cyclohexane and acetonitrile. The compound occurs in two crystal forms. It is an anhydrate melting at 74 ° C and a hemihydrate . [4] The hemihydrate is from about 35 ° C the water of hydration and converts thereby in the anhydrate form to. [4] The anhydrate crystallizes in a monoclinic lattice with the space group P 2 1 , and the hemihydrate crystallizes in a tetragonal lattice with the space group P 4 3 21 2. [4]

4  Kaihang Liu, Zhou Xinbo, Zhejing Xu, Bai Hongzhen, Jianrong Zhu Jianming Gu, Guping Tang, Liu Xingang, Hu Xiurong: anhydrate and hemihydrate of Tasimelteon: Synthesis, structure, and pharmacokinetic study in J. Pharm. Biomed. Anal. 151 (2018) 235-243, doi : 10.1016 / j.jpba.2017.12.035 .

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