Hajra Saumen

Asymmetric Aldol Reactions Hajra Saumen

Chiral auxiliary based and organocatalyzed aldol reactions have been used for the asymmetric synthesis of various natural products. These reactions steps have been used in synthesizing ?-butyrolactone containing natural products and their analogs. An asymmetric route for one-pot synthesis of trans- and cis-4,5-disubstituted-?-butyrolactones via reagent sequence controlled syn- and anti- aldol reactions of N-succinyl-2-oxazolidinone are described. Mechanistic studies are discussed. Using these asymmetric syn- and anti-aldol reactions of chiral N-succinyl-2-oxazolidinones, trans-paraconic acids and cis-paraconic acids are synthesized in both of their enantiomeric forms. Enantioselective one-pot synthesis of ?-(hydroxyalkyl)-?-butyrolactones employing cross-aldol reaction catalyzed by an organocatalyst is described. Efficient routes for the asymmetric synthesis of (-)-enterolactone, natural hydroxyenterolactone and its analog utilizing organocatalytic asymmetric cross-aldol reaction and C-alkylation as the key steps are achieved. Similar routes have provided chiral intermediates, which could be converted to epi-isohydroxymatairesinol and (7?R)-7?-hydroxymatairesinol.