合成路线1

Enantioselective synthesis of suvorexant is based on enzymatic transamination and described as follows. Cyclization of 2-amino-4-chlorophenol (XVI) with trimethyl orthoformate HC(OMe)3 in the presence of p-TsOH in THF provides 5-chlorobenzoxazole (XVII), which subsequently reacts with LiHMDS in THF followed by bromination of the resulting anion with NBS to afford 2-bromo-5-chlorobenzoxazole (XVIII). Condensation of crude bromo derivative (XVIII) with ethanolamine (XIX) in acetonitrile gives 2-(5-chloro-2-benzoxazolylamino)ethanol (XX), which is subjected to aza-Michael addition with methyl vinyl ketone (II) in the presence of NaOH in DMF to yield the β-amino ketone (XXI). Activation of crude alcohol (XXI) with MsCl in the presence of Et3N in i-PrOAc provides keto mesylate (XXII), which by transamination and cyclization with i-PrNH2 in the presence of CDX-017 enzyme and pyridoxal phosphate in DMSO, and subsequent acidification with HCl, provides the (R)-azepane derivative (XXIII). Finally, Schotten-Baumann acylation of amine (XXIII) with 5-methyl-2-(1,2,3-triazol-2-yl)benzoyl chloride (XXIV) in the presence of K2CO3 in i-PrOAc/H2O affords suvorexant. Chloride (XXIV) was prepared from 5-methyl-2-(1,2,3-triazol-2-yl)benzoic acid (IX) by treatment with (COCl)2 in the presence of DMF in i-PrOAc .