Ring C functionalised diterpenoids. Part VI. Solvolysis of ent-methyl 12β-p-tolylsulphonyloxybeyeran-19-oate

Abstract

The solvolysis of the title tosylate (1b) in buffered acetic, formic, and trifluoroacetic acids at room temperature is described. Acetolysis gave only products resulting from a single Wagner–Meerwein shift [the ent-14(13→12)-abeo-beyeranes (3b), (3e), (4), and (5)], whereas formolysis and trifluoroacetolysis gave products from further rearrangement in addition to the starting beyerane system [formates of the ent-12-methyl-17-noratisanol (2a) and the ent-beyeranol (1a); trifluoroacetates of (2a), (2d), and (1a)]. No product of intramolecular hydride shifts was observed. The rearrangements are discussed in terms of intermediate carbocation stabilities and lifetimes in the various solvents.