An efficient semisynthesis of 7-deoxypaclitaxel from taxine

A semisynthesis of 7-deoxypaclitaxel 4 is described, starting from taxine 6 – the most abundant naturally occurring taxane diterpene fraction. A key step in this transformation is a tandem reaction: stereoselective osmylation of cinnamic ester 14/intramolecularly assisted methanolysis of 16, which gives the key intermediate 5, along with the optically pure ester 17 – a precursor for the synthesis of the paclitaxel side-chain. In this way, the cinnamoyltaxicine 9 is converted into 7-deoxybaccatin III 25 in 11 steps, and in 15% overall yield.