合成路线1

Claisen reaction between ethyl caproate (I) and ethyl formate (II) in the presence of NaOEt affords formyl derivative (III), which is then condensed with O-benzyl hydroxylamine hydrochloride (IV) by means of NaOAc in EtOH/H2O to yield derivative (V). Hydrolysis of the ethyl ester moiety of (V) by treatment with aqueous NaOH in MeOH provides carboxylic acid (VI), which is coupled to tert-leucine N,N-dimethylamide (VII) by means of EDC and HOAt to furnish compound (VIII). Reduction of the oxime moiety of (VIII) with NaCNBH3 in HOAc affords a mixture of diastereoisomers from which (R)-(IX) is separated by flash chromatography. Finally, treatment of (R)-(IX) with N-formyl-benzotriazole (HCOBt) in THF provides formamide (X), whose benzyl group is then removed by hydrogenation over Pd/C in MeOH.