- USUS5856529 A
- USUS8785492 B2
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609799-22-6 cas, BMS-214778; VEC-162, ATC:N05CH03
- Use:Treatment of sleep disorder; Melatonin receptor agonist
- 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) in January 2014 for the treatment of non-24-hour sleep–wake disorder (also called Non-24, N24 and N24HSWD). In June 2014, the European Medicines Agency accepted an EU filing application for tasimelteon 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, 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. 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.
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. A phase III insomnia trial was conducted in 2006. A second phase III trial on insomnia, this time concerning primary insomnia, was completed in June 2008. In 2010, the FDA granted orphan drug status to tasimelteon, then regarded as an investigational medication, for use in totally blind adults with N24HSWD. (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. 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.
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. 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. 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).
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”.
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:
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.
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.
Tasimelteon has the chemical name: trans-N-[[2-(2,3-dihydrobenzofuran-4-yl)cycloprop-1yl]methyl]propanamide, has the structure of Formula I:
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
PREPARATION OF XV
XXIV D-camphorsulfonic acid IS REACTED WITH THIONYL CHLORIDE TO GIVE
…………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
TREATED WITH AMBERLYST15
….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
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
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
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.
SYNTHESIS CONSTRUCTION AS IN PATENT
Reaction Scheme 1
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
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
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
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
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
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
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
SEE ORIGINAL PATENT FOR CORECTIONS
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.
(±)-(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%).
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%).
(-)-(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.
FINAL PRODUCT TASIMELTEON
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
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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This preparation is referenced from:
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References and Notes
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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).
- US 6 214 869 (Bristol-Myers Squibb; 10.4.2001; appl. 25.5.1999; USA-prior. 5.6.1998).
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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.
|Bioavailability||not determined in humans|
|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|
|Chemical and physical data|
|Molar mass||245.32 g/mol|
|3D model (JSmol)|
DR ANTHONY MELVIN CRASTO Ph.D
GLENMARK SCIENTIST , NAVIMUMBAI, INDIA
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 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 .  The hemihydrate is from about 35 ° C the water of hydration and converts thereby in the anhydrate form to.  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 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 .