BIOMIMETIC TRANSFORMATIONS OF A GUAIANOLIDE-1(10)-BETA-EPOXIDE AND THE MOLECULAR-STRUCTURES OF 3 GUAIANOLIDES

A reinvestigation of the boron trifluoride-mediated transformations of the guaianolide-1(10)-beta-epoxide [1] provided the previously obtain ed cis-eudesmanolide [5] and the fluoroguaianolide [2] as well as two new lactones, the trans-guaianolide [4] and the cis-guaianolide [3]. T he molecular structures of compounds 1, 3, and 4 were determined by si ngle crystal X-ray diffraction. The mechanisms of formation of the fou r lactones from epoxide 1 can be formulated via the carbocationic inte rmediates A and B.