Brunner, Henri and Schmidt, Peter and Prommesberger, Markus (2000) Enantioselective catalysis. Part 133: Conformational analysis of amides of 9-amino(9-deoxy)epicinchonine. TETRAHEDRON-ASYMMETRY, 11 (7). pp. 1501-1512. ISSN 0957-4166
Full text not available from this repository. (Request a copy)Abstract
Amides of 9-amino(9-deoxy)epicinchonine have been used as chiral base catalysts to induce asymmetry in enantioselective decarboxylation reactions. To understand the reaction mechanism and to optimize the bases by variation of the amide substituents, a detailed knowledge of their preferred conformation is necessary. The conformations were investigated by H-1 NMR spectroscopy, X-ray analysis and semiempirical molecular orbital calculations. Principally, cinchona alkaloids may adopt four different conformations (Fig. 1), of which open b and open b' are preferred by 2-ethoxy-N-(9-deoxyepicinchonine-9-yl)benzamide 2 in solution. AM1 Calculations confirm these results, and the small energy barrier between the two open conformations explains their simultaneous existence in solution, Crystal structure analyses of various amides show open conformations in the solid state. Local minimum energy conformations were found for open conformations of the compound 2 protonated at the quinuclidine system, which is the active species in the enantioselective decarboxylation reaction. (C) 2000 Elsevier Science Ltd. All rights reserved.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | 9-AMINO(9-DEOXY)CINCHONA ALKALOIDS; CINCHONA ALKALOIDS; COMBINED NMR; DECARBOXYLATION; DERIVATIVES; COPPER(I); ACID; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Anorganische Chemie > Alumni or Retired Professors > Prof. Dr. Henri Brunner |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 17 May 2022 08:10 |
| Last Modified: | 17 May 2022 08:10 |
| URI: | https://pred.uni-regensburg.de/id/eprint/42573 |
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