合成路线1

The reaction of L-tert-leucine (I) with Boc2O and TEA in methanol gives N-Boc-L-tert-leucine (II), which is condensed with N,O-dimethylhydroxylamine (III) by means of CDI in dichloromethane to yield the corresponding amide (IV) (1). The reaction of (IV) with methyl lithium in THF affords the chiral methylketone (V), which is deprotected by means of TFA in dichloromethane to provide the aminoketone (VI). The condensation of (VI) with 2(R)-(benzyloxyaminomethyl)hexanoic acid (VII) by means of EDC and HOBt in DMF leads to the amide (VIII), which is formylated by means of formylacetic anhydride (IX) in dichloromethane to give the precursor (X). Finally this compound is deprotected by hydrogenation with H2 over Pd/C in ethyl acetate to afford the target compound. Alternatively, the intermediate chiral ketone (V) can also be obtained by reaction of N-Boc-L-tert-leucine pentafluorophenyl ester (XI) with methyl lithium of methylmagnesium bromide