Biomimetic Transformations of a Guaianolide-L(10)-β-Epoxide and the Molecular Structures of Three Guaianolides

Abstract

A reinvestigation of the boron trifluoride-mediated transformations of the guaianolide-1(10)-β-epoxide [1] provided the previously obtained cis-eudesmanolide [5] and the fluoroguaianolide [2] as well as two new lactones, the trans-guaianolide [4] and the cis-guaianolide [3]. The molecular structures of compounds 1, 3, and 4 were determined by single crystal X-ray diffraction. The mechanisms of formation of the four lactones from epoxide 1 can be formulated via the carbocationic intermediates A and B.