STUDIES ON THE PHOTOCHEMISTRY OF TAXOL(R)

Irradiation of taxol at 280 nm in a Rayonet reactor yielded a novel pentacyclic derivative containing a new bond between C-3 and C-II. The proposed mechanism involves a triplet intermediate and the first event of the oxa-di-pi-merhane rearrangement. Taxane derivatives that lack both the benzoate at C-2 and the benzamide function at C-3' do not undergo the rearrangement, suggesting the intervention of an intramolecular energy transfer. Irradiation at 300 nm also effects extrusion of the C-9 carbonyl, yielding a ring-contracted product.