Biosynthetic studies on blazeispirane and protoblazeispirane derivatives from the cultured mycelia of the fungus Agaricus blazei

The biosynthesis of blazeispirol A, an unprecedented skeleton, was investigated by feeding 13C-labeled acetates, propionate and methionine to the growing cultures of Agaricus blazei (Agaricaceae). 13C NMR spectral analysis demonstrated the mevalonate origin of the spiroacetal moiety and the dihydronaphthalene moiety. The O-methyl and 28-methyl groups of blazeispirol A were labeled by feeding l-[methyl-13C] methionine. The biosynthetic origin of blazeispirol A derived from ergosterol was directly demonstrated by the feeding experiment using the biosynthetically produced 14C labeled ergosterol. Furthermore, the hypothetical biogenesis of the blazeispirane and protoblazeispirane derivatives is discussed.