Stereoelectronically Controlled, Thallium(III)-Mediated C-19 Degradation of 19-Hydroxy Steroids. An Expedient Route to Estrone and its Congeners via 19-Nor-10.beta.-hydroxy Intermediates
摘要:
Estrone- (8b) has been synthesized in four steps from 3 beta-acetoxy-19-hydroxyandrost-5-en-17-one (2b), readily available from an industrial precursor. A key feature of the strategy is a stereoelectronically controlled, TI(III)-mediated degradation (2b --> 5b). Oppenauer oxidation of diol 6b, resulting from saponification of the acetate 5b, afforded the unsaturated 10 beta-hydroxy ketone 7b, acid treatment of which induced aromatization affording 8b. An alternative route including dehydration (5b --> 9b) followed by Oppenauer oxidation (10b --> 8b) gave comparable results. This strategy has first been developed with the aid of cholestane model compounds (2a --> 5a) and then successfully applied to the synthesis of analogues in the cholestane, androstane, and pregnane series to produce the corresponding 19-nor-10 beta-hydroxy derivatives 7a-d and A-aromatic steroids 8a-d.
Stereoelectronically Controlled, Thallium(III)-Mediated C-19 Degradation of 19-Hydroxy Steroids. An Expedient Route to Estrone and its Congeners via 19-Nor-10.beta.-hydroxy Intermediates
作者:Pavel Kocovsky、Richard S. Baines
DOI:10.1021/jo00097a056
日期:1994.9
Estrone- (8b) has been synthesized in four steps from 3 beta-acetoxy-19-hydroxyandrost-5-en-17-one (2b), readily available from an industrial precursor. A key feature of the strategy is a stereoelectronically controlled, TI(III)-mediated degradation (2b --> 5b). Oppenauer oxidation of diol 6b, resulting from saponification of the acetate 5b, afforded the unsaturated 10 beta-hydroxy ketone 7b, acid treatment of which induced aromatization affording 8b. An alternative route including dehydration (5b --> 9b) followed by Oppenauer oxidation (10b --> 8b) gave comparable results. This strategy has first been developed with the aid of cholestane model compounds (2a --> 5a) and then successfully applied to the synthesis of analogues in the cholestane, androstane, and pregnane series to produce the corresponding 19-nor-10 beta-hydroxy derivatives 7a-d and A-aromatic steroids 8a-d.
Mickova,R.; Syhora,K., Collection of Czechoslovak Chemical Communications, 1969, vol. 34, p. 458 - 467