合成路线1

N-Methyl-L-leucine (IV) was converted to tert-butyl ester (V) by treatment with isobutylene and H2SO4. Formation of the N,N-dialkyl derivative (VIII) was achieved by either alkylation of (V) with p-tert-butylbenzyl bromide (VI) or by reductive condensation of (V) with p-tert-butylbenzaldehyde (VII) and NaBH(OAc)3. Deprotection of the tert-butyl ester of (VIII) with trifluoroacetic acid gave amino acid (IX), which was activated as the mixed anhydride (X) upon treatment with isobutyl chloroformate and a polymer-supported morpholine base. Coupling of (X) with tyrosine amide (III) then afforded the title dipeptide amide. Unreacted starting materials were captured by the addition of polymer-supported polyamine and isocyanate resins.