ORGN 405 |
| Yu Takano and K. N. Houk. Department of Chemistry and Biochemistry, University of California Los Angeles, 405 Hilgard Ave., Los Angeles, CA 90095 |
| Lipases and esterases are enzymes hydrolyzing a variety of different esters. X-ray crystallographic structures of lipases and esterases with bound inhibitors indicate that a specific conformation of the tetrahedral intermediate mimic is present. We have explored the mechanism of the base promoted transesterification involving methoxy and methyl acetate. A conformational analysis of the tetrahedral intermediate, 1,1-dimethoxyethoxide, has been performed with density functional theory. The geometries were fully optimized with B3LYP/6-31+G(d) calculations. Only the gauche+-anti (anti-gauche-) and gauche+-gauche+ minima are formed, and the gauche+-anti conformation is more stable by 2.9 kcal mol-1. The origin of the conformational preference was investigated from the viewpoint of the hyperconjugation, electrostatic, and steric effects. On the other hand, the gauche+-gauche- conformation is found to be a transition state connecting the gauche+-anti and anti-gauche- conformations. |
|
Physical Organic, Materials, Heterocycles, Aromatics, Metal-Mediated Reactions
8:00 PM-10:00 PM, Tuesday, September 9, 2003 Hilton New York -- Americas Hall 1, Poster
Division of Organic Chemistry |