(25R)-5β-Hydroxyspirost-2-en-6-one

In the title compound, C₂₇H₄₀O₄, 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 usual in this type of compound. The D ring adopts a 13β,14α half chair and the E ring adopts a C22β,O3α half chair. The A/B ring junction is cis and the B/C and C/D ring junctions are trans.

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