合成路线1

Chiral tripeptide intermediate (XV): The deprotection of perhydropyridazine carboxylic acid methyl ester (VII) with TFA in dichloromethane gives ester (VIII), which is condensed with N-(benzyloxycarbonyl)-3-hydroxy-L-tyrosine (IX) by means of HBTU and TEA in acetonitrile to yield the dipeptide (X). The protection of the phenolic OH group of (X) with Boc2O and TEA In dichloromethane affords (XI), which is selectively deprotected with H2 over Pd/C in ethanol to provide dipeptide (XII). The condensation of (XII) with N-(benzyloxycarbonyl)-L-valine (XIII) by means of HBTU as before gives the protected tripeptide (XIV), which is finally treated with H2 over Pd/C in ethanol to provide the target tripeptide intermediate (XV)