Use of 1,3-dibenzyl-dihydrouracil in the chain extension of 2,3-O-isopropylidene-D-glyceraldehyde

A simple and stereodivergent approach to 5-trihydroxypropyl-dihydrouracil derivatives based on the aldol-type addition of 1,3-dibenzyl-dihydrouracil lithium enolate to 2,3-O-isopropylidene-D-glyceraldehyde is reported. The reaction was investigated in different solvents and under Lewis acid catalysis in order to establish the stereochemical preferences. The synthesis of enantiomerically pure (5S,1'S,2'R)-5-trihydroxypropyl-dihydrouracil derivative and its C-5 epimer was realized in good yields and diastereoselectivity. The synthesis of ureido polyols was obtained via the reductive heterocycle ring cleavage of these intermediates.