Epimerization at C-6 of polyfimctionalized 6a-eudesmanolides was achieved by chemical means, to obtain 6ikwdesmanolides and, after rearrangement, 6p-guaianolides. The epimerization process consists of the LiAU$ reduction of a 6a-lactone, selective pmtection of the hydroxymethylene group at C-12, oxidation and reduction at C-6 to epimerize this carbon, depro&&on at C-12 and finally, lactonization with @.trapropykunmonium perruthenate (TPAP) and Cmethylmorpholine N-oxide (NMO) in yields over SO??. The rearrangement of lp-hydroxy-6p-colartin allow us to obtain 2,3-dihydre6P-tide D. INTRODUCIION The 6P_sesquitapene lactones, scarce in nature4. are the object of interesting studies on the biogenesis of pseudoguaianolides and elemanolides. The chemistry5, photochemistry6, biomimetic synthesis' and biotransformation* of 6a-sesquiterpene lactones have been extensively studied. We have reported the synthesis of 6p-sesquiterpene lactones by chemical and microbiological means9 and have obtained the lactone fimction with the aid of two microorganisms, which &uctionalized non-lactone sesquiterpene compounds10 at C-11 or C-12. a-sautoniu (1) is the classical starting material to obtain 6P_eudesmanolides, because it epimerizes iu acidic medium1 l. The special &mztionalization and the steric energy of a-sautoniu (1) is about 2.1 KcaVmol greaterI than that of its epimer at C-6. However, a more general method of epimeriziug this type of compounds at C-6, especially those with knctionalization at C-l, would allow us to synthesize other 6psesquiterpenolide compounds with different skeletons. This type of process is also possible with a-santoniu, but the transference of functionalization 6om C-3 to C-1 is not easy9a.