Stereoselective Syntheses of (+)-2-epi-Deoxoprosopinine, (-)-Deoxoprosophylline, (+)-cis-195A, and 2,5-Di-epi-cis-195A from a Common Chiral Nonracemic Building Block
| Autor: | Andrew G. H. Wee, Krishna Annadi |
|---|---|
| Rok vydání: | 2015 |
| Předmět: |
Allylic rearrangement
Lactams Lactol Stereochemistry Stereoisomerism Quinolones 010402 general chemistry 01 natural sciences chemistry.chemical_compound Lactones Alkaloids Piperidines Addition reaction Bicyclic molecule Molecular Structure 010405 organic chemistry Organic Chemistry Decarbonylation Bridged Bicyclo Compounds Heterocyclic 0104 chemical sciences chemistry Cyclization Lactam Quinolines Stereoselectivity |
| Zdroj: | The Journal of organic chemistry. 80(10) |
| ISSN: | 1520-6904 |
| Popis: | Approaches toward the syntheses of alkaloids belonging to the 2,6-disubstituted 3-hydroxypiperidine and cis-decahydroquinoline (cis-DHQ) classes of alkaloids are developed, starting from a common chiral nonracemic bicyclic lactam lactone (BLL). Two key δ-lactam intermediates, (5S,6S)-5-hydroxy-6-hydroxymethyl- and (5S,6S)-5-hydroxy-6-methylpiperidin-2-ones, are prepared; the latter δ-lactam is obtained via a direct decarbonylation of a bicyclic lactam lactol. The BLL is also used to prepare (4aR,5R,8aS)- and (4aR,5S,8aS)-5-methyloctahydroquinolin-2-ones, which involved a 6-exo-trig free-radical conjugate addition reaction. The stereoselectivity observed in the free-radical cyclization step is found to be governed by allylic 1,2-strain arising from the interaction of the N-(p-methoxybenzyl) group and the C6 substituent in the lactam ring of the free-radical intermediate. The effectiveness of the developed approaches is demonstrated by the asymmetric syntheses of (+)-2-epi-deoxoprosopinine, (-)-deoxoprosophylline, (+)-cis-195A, and 2,5-di-epi-cis-195A. |
| Databáze: | OpenAIRE |
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