合成路线1

Condensation of 4-methylpentanoyl chloride (I) with (S)-4-benzyl-2-oxazolidinone using n-BuLi afforded the N-acyloxazolidinone (III). Asymmetric alkylation of (III) with tert-butyl bromoacetate and LDA gave (IV), and subsequent removal of the chiral auxiliary by hydrolysis with lithium peroxide yielded (R)-2-isobutylsuccinic acid mono tert-butyl ester (V). This was further alkylated with allyl bromide (VI) and LDA to provide the (R,R)-2,3-disubstituted succinate (VII). Epimerization of (VII) to the required (2R,3S)-isomer (VIII) was accomplished by treatment with LDA and Et2AlCl. Benzyl ester (IX) was then prepared by reaction of (VIII) with benzyl bromide and DBU. Hydroboration of the olefinic double bond of (IX) by means of 9-borabicyclononane, followed by oxidative treatment with H2O2 gave rise to the primary alcohol (X). This was converted to carbonate (XI) upon reaction with p-nitrophenyl chloroformate and N-methylmorpholine (NMM). Coupling of (XI) with lysine derivative (XII) then yielded carbamate (XIII).