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Synthesis 2006(6): 975-978  
DOI: 10.1055/s-2006-926356
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© Georg Thieme Verlag Stuttgart · New York

Two Novel Approaches toward Stereoselective Introduction of β-Hydroxy­methyl Group at the C-7 Position of 5-Androstene

Qin Gu, Yun-Hong Zheng, Yuan-Chao Li*
Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 555 Zu Cong Zhi Road, Zhangjiang Hi-Tech Park, Shanghai 201203, P. R. of China
Fax: +86(21)50807288; e-Mail: ycli@mail.shcnc.ac.cn;
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Publication History

Received 28 September 2005
Publication Date:
27 February 2006 (online)

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Abstract

Two novel approaches to stereoselective introduction of 7β-hydroxymethyl group onto 5-androstene have been developed. In the first approach, coupling of benzyloxymethyl chloride with the 7-carbonyl group of 1 mediated by SmI2 gives, after debenzylation, two isomers 4 and 5 respectively, which are stereoselectively deoxygenated by means of an ionic hydrogenation to afford 6. The second approach involves the addition of (isopropoxydimethylsilyl)methyl Grignard reagent (Tamao’s reagent) to the 7-carbonyl group of 1, followed by oxidative cleavage of the silicon-carbon bond by hydrogen peroxide giving compound 5. Stereoselective deoxygenation of 5 via an ionic hydrogenation also affords 6. The relative configuration of 6 is confirmed by ROESY studies.

Key words

steroids - stereoselective - 7β-hydroxymethyl - 5-androstene - ionic hydrogenation