Conjugate addition of sodium hypophosphite to dibenzyl alpha-methyleneglutarate (I) afforded the phosphonate (II), which was converted to the benzyl-protected compound (III) by treatment with benzyl alcohol in the presence of pivaloyl chloride. Deprotonation of (III) with NaH followed by conjugate addition to (I) provided the pentabenzyl ester (IV). Finally, hydrogenolysis of the benzyl ester groups of (IV) using H2 over palladium hydroxide gave rise to the title compound.