A novel chiral synthesis of the CD-ring 2 of 1α,25-dihydroxyvitamin D3 (1a) is described. The optically active D-ring keto ester 3c was prepared by reductive cleavage of 6-oxonorbornane-2-carboxylate 4c with lithium naphthalenide. 1,2-Transposition of enone 15, which was obtained by Robinson annulation of 14, was accomplished via thermolysis of the allylic carbonate 29 at 100°C to give enone 16. Reduction of ketone 16 with NaBH4-CeCl3 followed by hydrogenation with RhCl-(PPh3)3 catalyst gave trans-indanol 32, which was transformed to intermediate 2.
|ジャーナル||Journal of Organic Chemistry|
|出版物ステータス||Published - 1993|
ASJC Scopus subject areas
- Organic Chemistry