ORGN 547 |
| Asymmetric aminocatalysis has emerged as a successful vehicle for accomplishing a wide variety of highly enantioselective organic transformations. Mechanistic analogies to enzymes, including the importance of hydrogen bonding, have recently been highlighted in a number of cases. We recently proposed a novel variation of these hydrogen bonding themes in recent kinetic, mechanistic and computational studies of the proline-mediated alpha-aminoxylation and alpha-amination of aldehydes. Observation of an accelerating rate that is proportional to product concentration led us to propose that the active catalyst is a product-proline adduct exhibiting multi-dentate hydrogen bonding. The product-proline adduct helps to stabilize a key proton transfer transition state in the addition of aldehyde to proline, relative to the same reaction unassisted by product. The example of a reaction product enabling higher efficiency in its own catalytic production may help us understand how small molecule amino acid catalysts evolved into highly efficient enzymes. |
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Asymmetric Reactions and Syntheses
1:00 PM-5:00 PM, Wednesday, 31 August 2005 Washington DC Convention Center -- 201, Oral
Division of Organic Chemistry |