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Six taxine alkaloids were isolated from Taxus baccata needles and partially separated. An HPLC method for the analysis of the taxine fraction was developed. By NMR and deamination/hydrolysis studies it was established that the taxine fraction consisted mostly of taxicin-I and taxicin-II derivatives in a variable ratio. Four of the six taxine alkaloids isolated have not been reported before. All of the alkaloids were found to be unstable under neutral and basic conditions, and some of them were very easily interconverted.

During the large-scale synthesis of an O-cinnamoyltaxicin I acetonide, an intermediate for the semisynthesis of 7-deoxypaclitaxel derivatives, side-product 3 was formed via a vinylogous retro-aldol reaction and a long-range hydride shift from O-cinnamoyltaxicin I (1) under alkaline reaction conditions. Compound 3 has two hemi-acetal bridges at C-1,C-9 and C-10,C-13. Compound 4 was formed from side-product 3 under acidic reaction conditions and is the first C-13 spiro-taxane described in the literature. This spiro-taxane has two acetal bridges between C-1,C-13 and C-10,C-13.