Ring c functionalised diterpenoids. Part V. Preparation and formolysis of (16S)-ent-12β-p-tolylsulphonyloxykaurane and the (16S)-ent-13-p-tolylsulphonyloxyatisanes

Abstract

The preparation and characterisation of the ring C functionalised (16S)-ent-kauranols (1a and b) and (4a and b) and (16S)-ent-atisanols (2a and b), and the corresponding ketones (1c), (4c), and (2c) are described. The room temperature formolysis of the toluene-p-sulphonate esters of (1a), (2a), and (2b)[(1d), (2d), and (2e), respectively] followed by basic hydrolysis, gives mixtures which contain products [(7a), (7b), and (9)] of 1,3-hydride shift. It is suggested that a classical bicyclo[2.2.2]octyl-type cation (F) is a significant intermediate in these solvolyses, and that differences in the amounts of hydride shift products obtained from (1d) on the one hand, and (2d) and (2e) on the other, result from differing degrees of solvation of (F).