Taxine. Part VII. The stereochemistry of hydrogenolysis of O-β-phenylpropionyltaxicin-I

Abstract

The hydroxycyclohexane-1,2-dicarboxylic acids (11) and (16), of known configuration, were converted into their deoxy-analogues, (9) and (7), respectively. The cyclohexanedicarboxylic acid (7) was also obtained, without change of configuration, by oxidation of the dialdehyde (4), which is a product of periodate cleavage of 5-deoxy-4,16-dihydrotaxicin-I. The latter must therefore have the 4α-configuration (2; R = H), unlike the normal 4,16-dihydrotaxicin-I derivatives, e.g., (1; R = H), which have the 4β-configuration. The 4 α-configuration of (2; R = H) is attributed primarily to the need for inversion of configuration at the hydrogenolysis centre when a palladium catalyst is used.