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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.

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Aswini Kumar Giri: Assist. Res. Scientist: U of A, Tucson, USA. Postdoc Research: WSU, Pullman & U of A, USA. PhD: Org. Chem., IIT-Kharagpur, India. Saumen Hajra: Prof. of Chemistry, IIT-Kharagpur, India. AvH Fellow: University of Wuerzburg, Germany. Postdoc Research: North Dakota State University, USA. PhD: NCL, University of Pune, India.

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