合成路线1

Allyl ester (IV) is subjected to Claisen-Ireland rearrangement in the presence of strong bases to produce a diastereomeric mixture of pentenoic acids, from which the desired isomer (IX) can be isolated via crystallization of its (S)-phenylethylamine salt. Subsequent coupling of acid (IX) with tert-leucine methylamide (X) provides amide (XI). Oxidative cleavage of the terminal olefin of (XI) to aldehyde (XII) is performed by either treatment with NaIO4 or by ozonolysis. Aldehyde (XII) is further oxidized to the carboxylic acid (XIII) employing NaClO2. Coupling of acid (XIII) with O-benzyl hydroxylamine yields the benzyl-protected hydroxamate (XIV). The title compound is finally obtained by hydrogenolysis of the benzyl groups of (XIV) in the presence of Pd/BaSO4.