Novel rearrangement of an isocaryolane sesquiterpenoid under Mitsunobu conditions

Under modified Mitsunobu reaction conditions, a novel skeleton rearrangemen t; of terpenes has been obtained. The reactivity of 8,9-dioxygenated isocar yolane derivatives has been investigated. When either (8R,9R)-8-methoxyisoc aryolane-9-ol (7) or (8R,9R)-isocaryolane-8,9-diol (10) are treated under a cidic conditions, isocaryolan-9-one (9) and the rearrangement compound (1S, 2S,5R,8S)-1,4,4-trimethyltricyclo[6.2.1.0(2.5)]undecane-8-carbaldehyde (11) are obtained. Otherwise treatment of compounds 7 and 10 under modified Mit sunobu conditions leads to the novel sesquiterpene derivative (1S,2S,5R,9R) -1,4,4-trimethyltricyclo[7.2.1.0(2.5)] (8). This is the first example, to o ur knowledge, of a Mitsunobu-induced pinacol rearrangement. The influences of the substrate and reaction conditions on the evolution of the reaction a re both explored. This modification of the Mitsunobu reaction conditions in troduces a new, one-pot, procedure for preparing this class of rearrangemen t product.