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

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. (C) 2002 Elsevier Science Ltd. All rights reserved.