合成路线1

The alkylation of diethyl (R)(+)-2-hydroxysuccinate (I) with 2-methylallyl bromide (II) by means of LiHMDS in THF gives the alkylated diester (III), which is hydrolyzed with KOH in dioxane/water to yield the chiral succinic acid (IV). The regioselective monoesterification of (IV) with benzyl alcohol (V), trifluoroacetic anhydride, TEA and DMAP affords the monobenzyl ester (VI). The lactonization of (VI) by means of bis(2-oxo-3-oxazolidinyl)phosphinic chloride (BOPC) in dichloromethane provides the beta lactone (VII), which is hydrogenolyzed at the benzyl ester group by means of H2 over Pd/C in ethanol to give the carboxylic acid (VIII). Finally this compound is condensed with the dipeptide N2-(tert-butoxycarbonyl-L-alanyl)-N1-(1-naphthylmethyl)-L-lysinamide (IX) by means of DCC and HOBt in dichloromethane to yield the target dipeptide derivative.