合成路线1

The reaction of 2-butylmalonic acid (I) with piperidine and formaldehyde in refluxing ethanol gives 2-methylenehexanoic acid (II), which is condensed with the chiral auxiliary oxazolidine lithium salt (III) by means of pivaloyl chloride and TEA to yield the oxazolidide (IV). The addition of O-benzylhydroxylamine (V) to (IV) by means of Ts-OH proceeds with great stereospecificity, affording tosylate (VI), which is submitted to cleavage of the chiral auxiliary with LiOH in aqueous THF to provide the carboxylic acid (VII). The formylation of the benzylhydroxylamine group of (VII) with HCOO-Ac in THF gives the formamide (VIII), which is condensed with L-tert-leucine dimethylamide (IX) by means of HOAt and EDC in DMF to yield the pseudo dipeptide (X). Finally, this compound is debenzylated by hydrogenation with H2 over Pd/C in ethanol.