合成路线1

Reaction of N-acetyl-L-tyrosine (VIII) with tert-butyldimethylsilyl chloride and N-methylmorpholine (NMM), followed by phosphitylation with dibenzyldiisopropylamine phosphoramidite produced the intermediate phosphite ester (IX), which was oxidized to phosphate (X) using tert-butyl hydroperoxide. Subsequent coupling of (X) with protected leucine (XI) in the presence of DCC and HOBt afforded dipeptide (XII). Deprotection of the allyl ester of (XII) by means of Pd(PPh3)4 and pyrrolidine provided acid (XIII). After conversion of (XIII) to the corresponding mixed anhydride with isobutyl chloroformate, condensation with the chiral amine (VII) yielded amide (XIV). Finally, the benzyl ester groups of (XIV) were eliminated by catalytic hydrogenation over Pd/C.