2 STEROIDAL EPIMERS, -ALPHA)-PREGNA-20-YNO[3,4-C][1,2,5]OXADIAZOL-17-OL (THE 5-BETA-EPIMER) AND -ALPHA)-PREGNA-20-YNO[3,4-C][1,2,5]OXADIAZOL-17-OL (THE 5-ALPHA-EPIMER)
Dr. Lisgarten et al., 2 STEROIDAL EPIMERS, -ALPHA)-PREGNA-20-YNO[3,4-C][1,2,5]OXADIAZOL-17-OL (THE 5-BETA-EPIMER) AND -ALPHA)-PREGNA-20-YNO[3,4-C][1,2,5]OXADIAZOL-17-OL (THE 5-ALPHA-EPIMER), Acta crystallographica. Section C, Crystal structure communications, 51, 1995, pp. 666-670
The crystal and molecular structures of the steroidal oxadiazoles (5 b
eta,17 alpha)-pregna-20-yno[3,4-c][1,2,5]oxadiazol-17-ol (the 5 beta-e
pimer) and (5 alpha,l7 alpha)-pregna-20-yno[3,4-c][1,2,5]oxadiazol-17-
ol (the 5 alpha-epimer), C21H28N2O2, have been determined. In both str
uctures rings A are similar, having conformations intermediate between
a strained sofa, a half-chair and an envelope. Rings B and C are also
similar, adopting chair conformations. In the 5 beta-epimer, ring D h
as a 13 beta-envelope conformation, while in the 5 alpha-epimer, ring
D has an envelope/intermediate half-chair conformation.