合成路线1

The protected 4-pyrimidinylphenylalanine (III) was prepared by palladium-catalyzed coupling of the boronophenylalanine (I) with the 5-halopyrimidine (II). After acidic cleavage of the N-Boc protecting group of (III), the resultant amino ester (IV) was coupled with N-Boc-cycloleucine (V) to provide dipeptide (VI). Further acidic treatment of (VI) removed the N-Boc group to yield amine (VII). The chiral bromo acid (IX) was obtained by diazotization of D-valine (VIII) in the presence of HBr and KBr. Acylation of the racemic amine (VII) with bromo acid (IX) furnished the corresponding amide (X) as an epimeric mixture. The bromo group of (X) was finally displaced with potassium thioacetate to give the title thioacetate ester.