Synthesis of 22-Cupriosteroids, a New Route to Steroids Possessing Oxygenated Side Chains

✍ Scribed by Scherlitz-Hofmann, Ina ;Bößneck, Ulrich ;Schönecker, Bruno

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 591 KB
• Volume: 1996
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199619960211

✦ Synopsis

Abstract

A new method for the synthesis of steroids with oxygenated side chains starting from C~22~ steroids is described. Rieke copper, obtained by reduction of lithium 2‐thienylcyanocuprate 4 with lithium naphthalenide at −78°C or −100°C, reacts with the 22‐bromosteroids 1a, 2, 14 to afford the corresponding cupriosteroids. In addition to the metalation a very smooth retro Diels‐Alder reaction takes place in the case of 14 at the B ring. The steroid‐copper compounds react with (±)‐1,2‐epoxypropane to furnish epimeric mixtures of the 24‐hydroxysteroids 6, 8 and 15 in good yields. The procedure described is useful for a short synthesis of (24__R__)‐cholesta‐5,7‐diene‐3β,24,25‐triol (17, as 3‐silyl ether), the provitamin of the main metabolite (24__R__)‐24,25‐dihydroxyvitamin D~3~, using 14, Rieke copper and the highly functionalized chiral building block 10/n‐butyllithium.