Terpenoids. Part XVIII. A common stereoelectronic requirement in epimerisations and retro-Dieckmann-type cleavages of some diterpene alcohols and ketones

Abstract

A stereoelectronic factor controlling epimerisations of the C-15 alcohols (2)—(5) derived from enmein (1)(which have a cis-relationship between the 15-hydroxy- and 16-methyl groups) into the corresponding trans-alcohols (6)—(9) also operates in the retro-Dieckmann-type cleavage of the related C-15 ketones (30) and (10) to give the carboxylic acids (31) and (33). The mechanism of these reactions is discussed.