A Ready Conversion of a Pregnane-20-carboxaldehyde to 17α-Hydroxypregnan-20-ones and Pregn-16-en-20-ones

✍ Scribed by Biancini, Bruno ;Caciagli, Valerio ;Centini, Felice ;Eletti-Bianchi, Giancarlo ;Re, Luciano

• Book ID: 102366735
• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 412 KB
• Volume: 1982
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.198219821007

✦ Synopsis

Abstract

Reaction of (20__S__)‐5α‐chloro‐3β‐hydroxypregnane‐20‐carboxaldehyde (9, prepared in two steps from stigmasterol) with oxygen and potassium tert‐butoxide, followed by trimethyl phosphite treatment, afforded 5α‐chloro‐3β,17α‐dihydroxypregnan‐20‐one (6) and 3β,17α‐dihydroxypregn‐5‐en‐20‐one (7). This mixture was converted into 7 by potassium hydroxide treatment, and into 17α‐hydroxypregn‐4‐ene‐3,20‐dione (8) by reaction with pyridinium dichromate followed by potassium hydroxide treatment. Bromination‐dehydrobromination of 9, in one or two steps, afforded (Z)‐ and (E)‐5α‐chloro‐3β‐hydroxypregn‐17(20)‐ene‐20‐carboxaldehyde (11). Reaction of 11 with oxygen and potassium hydroxide gave 5α‐chloro‐3β‐hydroxypregn‐16‐en‐20‐one (12), which was converted to 3β‐hydroxypregna‐15,6‐dien‐20‐one (13) by further potassium hydroxide treatment, and to pregna‐4,16‐diene‐3,20‐dione (14) by Oppenauer reaction using excess aluminium isopropoxide.