合成路线1

Amino acid (II) (obtained by N-alkylation of N-Boc-D-phenylalanine (I) with MeI), was coupled to (S)-1-amino-2-propanol (III) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide-HCl (EDC) and 1-hydroxybenzotriazole to give amide (IV). The N-Boc group of (IV) was then deprotected with trifluoroacetic acid in CH2Cl2 to afford (V). Further coupling of (V) with D-naphthylalanine derivative (VI), followed by Boc deprotection with trifluoroacetic acid, provided dipeptide amide (VII). This dipeptide was coupled to intermediate amino acid (VIII) using EDC and 1-hydroxy-7-azabenzotriazole yielding tripeptide (IX). Finally, trifluoroacetic acid-promoted Boc-deprotection of (IX) provided the target compound. Intermediate amino acid (VIII) was prepared from 3-(tert-butoxycarbonylamino)-3-methylbutanoic acid (X) upon conversion to the mixed anhydride with ethyl chloroformate, followed by reduction to alcohol (XI) with LiBH4. Subsequent Swern oxidation of the alcohol (XI) furnished aldehyde (XII). This was condensed with triethyl phosphonoacetate, and then saponified with LiOH to produce the intermediate (VIII).