合成路线1

Title compound has been prepared by several related ways. Alkylation of methyl acetoacetate (I) with n-heptyl bromide (II) in the presence of NaOMe in refluxing MeOH yielded (III), which was brominated in CHCl3 at 0 C to give (IV). Subsequent reaction with triphenylmethyl mercaptan (V) and tetrabutyl ammonium hydroxide in toluene at r.t. provided (XI). Alternatively, beta-ketoester (XI) was prepared from a-mercaptoacetic acid (VI). Thus, protection as the S-trityl compound (VIII) by treatment with triphenylcarbinol (VII) and TFA, followed by condensation with N,O-dimethyl hydroxylamine in the presence of EDC and HOBt afforded N-methoxyamide (IX). Then, Claisen condensation with methyl nonanoate (X) using LDA as the base in THF at -78 C provided ketoester (XI). In order to avoid b-ketoacid decarboxylation, ketone (XI) was reduced to alcohol (XV) with NaBH4 in MeOH at 0 C. This hydroxyester was also prepared by a related route, consisting of protection of methyl mercaptoacetate (XII) as the S-trityl compound (XIII), followed by reduction to aldehyde (XIV) with DIBAL-H and condensation with methyl nonanoate (X). Saponification of methyl ester (XV) with KOH yielded hydroxyacid (XVI). Subsequent coupling with tert-butylglycine amide (XVII) using EDC and HOBt as the condensing agents produced amide (XVIII). Ketoamide (XX) was then obtained by oxidation with Dess-Martin periodinane (XIX). Finally, deprotection of the S-trityl group was effected by trifluoroacetic acid treatment under reducing conditions with triethyl silane to provide the target compound.