合成路线1

Horner-Emmons condensation of aldehyde (X) with Z-alpha-phosphonoglycine trimethyl ester (XI) furnished the unsaturated amino ester (XII). The required saturated compound (XIII) was then prepared by asymmetric hydrogenation of (XII) in the presence of a rhodium chiral catalyst. Removal of the p-methoxybenzyl protecting group of (XIII) was achieved by treatment with cerium ammonium nitrate yielding pyrrolidinone (XIV). Treatment of (XIV) with triethyloxonium tetrafluoroborate produced the cyclic imidate (XV), which was converted to amidine (XVI) by reaction with ammonium chloride. Finally, acid hydrolysis of the ester and carbamate groups of (XVI) provided the title compound.