Naidu S. Chowdari

Proline-catalyzed asymmetric assembly reactions: enzyme-like assembly of carbohydrates and polyketides from three aldehyde substrates☆

Abstract Directed asymmetric assembly of simple achiral building blocks into stereochemically complex molecules like triketides has been described for the first time using l -proline catalyzed asymmetric double aldol reactions. The product pyranoses contain four asymmetric centers constructed under proline catalysis in a highly diastereoselective and modestly enantioselective fashion from three aldehyde molecules. These results suggest that the construction of complex products from simple starting materials is within the realm of organocatalysis involving the simple naturally occurring amino acid l -proline. Our successful assembly of pyranoses from simple aldehydes under proline catalysis suggests that this approach may warrant consideration as a prebiotic route to sugars and polyketides.

Amine-catalyzed direct self Diels–Alder reactions of α,β-unsaturated ketones in water: synthesis of pro-chiral cyclohexanones

Abstract Amine-catalyzed direct self Diels–Alder reactions of α,β-unsaturated ketones have been developed. ( S )-1-(2-Pyrrolidinyl-methyl)pyrrolidine, l -proline and pyrrolidine catalyzed the reaction of α,β-unsaturated ketones to provide cyclohexanone derivatives with good yield (up to 80%) in a single step via in situ-generation of 2-amino-1,3-butadienes and iminium ion-activated enones. Pro-chiral cyclohexanones were selectively prepared with pyrrolidine catalysis in water.