(25R)-5β-Hydroxyspirost-2-en-6-one

Abstract

In the title compound, C 27 H 40 O 4 , the presence of a double bond between C2 and C3 forces ring A to adopt a 10α,5β half-chair conformation. The B, C and F rings have chair conformations, as is usual in this type of compound. The D ring adopts a 13β,14α half-chair conformation and the E ring a C22β,O3α half-chair conformation. The A/B ring junction is cis and the B/C and C/D ring junctions are both trans.