NAD(P)H models XV. Reduction of Δ4-3-ketosteroids via their iminium salts, by 1,4-dihydropyridine derivatives
✍ Scribed by Ronald A. Case; Upendra K. Pandit
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 607 KB
- Volume
- 99
- Category
- Article
- ISSN
- 0165-0513
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✦ Synopsis
Abstract
Pyrrolidinium salts derived from a series of 17‐substituted Δ^4^‐3‐ketosteroids are reduced by 1‐benzyl‐1,4‐dihydronicotinamide (BNAH) and 2,6‐dimethyl‐3,5‐diethoxycarbonyl‐1,4‐dihydropyridine (Hantzsch ester, 1 eq.) to the corresponding isomeric 5α‐ and 5β‐enamines which hydrolyse to the corresponding 3‐ketosteroids. In the case of the Hantzsch ester reduction, proton transfer from the oxidized Hantzsch ester to the enamine results in the formation of iminium salts, which are further reduced to the corresponding ammonium salts. Mechanistic, stereochemical and biochemical implications of the reactions are discussed.