STUDIES ON THE PHOTOCHEMISTRY OF TAXOL(R)

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