Stereoselective synthesis of cyclopentanones by reductive cleavage of 6-oxonorbornane-2-carboxylates and its application to the synthesis of 1.alpha.,25-dihydroxyvitamin D3 CD ring
摘要:
A novel chiral synthesis of the CD-ring 2 of 1alpha,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-degrees-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.
Stereoselective synthesis of cyclopentanones by reductive cleavage of 6-oxonorbornane-2-carboxylates and its application to the synthesis of 1.alpha.,25-dihydroxyvitamin D3 CD ring
摘要:
A novel chiral synthesis of the CD-ring 2 of 1alpha,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-degrees-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.
.alpha.-Methoxylation of Unsaturated Carbonyl Compounds
作者:Albert Feuerer、Theodor Severin
DOI:10.1021/jo00099a037
日期:1994.10
alpha-Methoxylation of enals or enones can be performed in high yield by a simple one-pot reaction sequence: Bromination of unsaturated hydrazones, HBr-elimination, and addition of methanol leads to the formation of beta-bromo-alpha-methoxy hydrazones (11), which after hydrolysis and HBr-elimination yields the alpha-methoxy enals or alpha-methoxy enones (13), respectively.
Wenkert,E. et al., Synthetic Communications, 1973, vol. 3, p. 205 - 209
作者:Wenkert,E. et al.
DOI:——
日期:——
Feuerer Albert, Severin Theodor, J. Org. Chem, 59 (1994) N 20, S 6026-6029