Studies Directed to the Synthesis of the Unusual Cardiotoxic Agent Kalmanol. Enantioselective Construction of the Advanced Tetracyclic 7-Oxy-5,6-dideoxy Congener
| Autor: | Stephane Borrelly, Leo A. Paquette |
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| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 118:727-740 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja9533454 |
| Popis: | The first synthesis of a highly functionalized B-homo-C-nor grayanotoxin closely related to kalmanol is reported. An enantiocontrolled route to the diquinane sector was first developed from (4R)-(+)-tert-butyldimethylsiloxycyclopentenone by taking advantage of the Michael acceptor properties of this enone and an α,β-unsaturated ester subsequently derived from it, viz., 4 → 7 → 8. These experiments formed the basis for more advanced substitution of the bicyclo[3.3.0]octane core. In fact, ready access was gained to the α-hydroxy esters 24−27. In these advanced intermediates, it is imperative that the acetyl and carbomethoxy groups bear a trans 1,3-relationship. The neighboring OR substituent should preferably be larger than methoxy in order to guarantee 100% facial selectivity during the ensuing capture by 1 (as its lithiated derivative). This condensation leads unidirectionally to tricyclic lactones represented by 30 and 31 and sets the stage for implementation of sequential Tebbe olefination and Claisen r... |
| Databáze: | OpenAIRE |
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