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Synlett 1991; 1991(6): 412-414
DOI: 10.1055/s-1991-20746
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Stereoselective Free Radical Reactions at C(20) of Steroid Side Chains

David J. Hart* , Ramanarayanan Krishnamurthy
  • *Department of Chemistry, The Ohio State University, 120 W. 18th Ave., Columbus, Ohio 43210, USA
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Publication Date:
07 March 2002 (online)

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Reduction (5 → 2 → 6+7) and allylation (5 → 2 → 8+9) of a C(20) steroidal α-carbethoxy free radical 2, prepared from ethyl 3β-(tert-butyldimethylsiloxy)-20-phenylseleno-5-pregnen-21-oate (5), can be accomplished with 7:1 and 9:1 diastereoselectivities (20R:20S), respectively. Deuteration (4 → 3 → 6+7) and alkylation (4 → 3 → 8+9) of the corresponding enolate 3, prepared from ethyl 3β-(tert-butyldimethylsiloxy)-5-pregnen-21-oate (4), followed the same stereochemical course with 3:1 and 31:1 diastereoselectivities (20R:20S), respectively.

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