The acetyl derivative of humirianthol

The title compound, 15α-acetato-3β,20:14β,16-di­epoxy-3α-hydroxy-9-epi-7-pimaren-19,6β-olide, C22H28O7, formed from the acetyl­ation of humirianthol, isolated from the tubers of Humirianthera ampla, crystallizes in the chiral space group P212121. The absolute configuration was set using the absolute configuration of C15, as determined by the Horeau method. The structure comprises a pimarane ring system with a methyl­ene ether bridge over ring A, a double bond in ring B, and two five-membered furan­yl rings, one fused to rings A and B and the other to ring C.