Lucibufagins. 2. Esters of 12-oxo-2β, 5β, 11.±-trihydroxybufalin, the major defensive steroids of the firefly Photinus pyralis (Coleoptera: Lampyridae)1a

Abstract

Fireflies of the species Photinus pyralis (Coleoptera: Lampyridae) are shown to contain a group of closely related steroidal pyrones, named lucibufagins, which serve a defensive role. The five major steroids from this insect are characterized as esters (5, 6, 7, 11, 12) of 12-oxo-2β, 5β, 11 α-trihydroxybufalin (9), chiefly on the basis of detailed spectral analyses. Selective proton decoupling 13C NMR experiments played a key role in making these structural assignments. These insect-derived steroids are the first bufadienolides to be isolated and characterized from an invertebrate source. © 1979, American Chemical Society. All rights reserved.