First Synthesis of a C-Homosteroid from Pregn-4-ene-3,11,20-trione

[摘要]：(3 alpha,5 alpha)-3-Hydroxy-C-homopregnane-11,20-dione (3) was prepared in eleven steps from the commercially available pregn-4-ene-3,11,20-trione (4) via the 11-oxo-13-formyl-12,13-secopregnane intermediate 11 (Scheme 2). Subjection of this secopregnane to an intramolecular aldol condensation afforded the alpha,beta-unsaturated key intermediate C-homopregn-12-en-11-one 12.

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