Three New Triterpenoids Containing Four-Membered Ring from the Fruiting Body of Ganoderma sinense

Methyl ganosinensate A (1), ganosinensic acid A (1a), and ganosinensic acid B (2), three new triterpenoids with an unusual four-membered ring skeleton produced by a bond across C-1 to C-11, were isolated from the fruiting body of Ganoderma sinense. Their structures were established on the basis of extensive spectroscopic methods, including 1D and 2D NMR techniques, and methyl ganosinensate A was confirmed by X-ray crystallographic analysis.