Terpenoids. Part VI. Preparation of ent-[13,14α-2H2]kaur-16-ene and some derivatives; bridgehead enolisation of ent-17-nor[13,14α-2H2]kauran-16-one

Abstract

Rearrangement of the phenylsulphonylhydrazone of ent-beyeran-16-one (ent-13-methyl-17-nor-8β,13β-kauran-16-one)(17) with sodium methoxide in methan[²H]ol yielded ent-[16-²H]beyer-15-ene (11), ent-[13,14α-²H₂]kaur-16-ene (5), ent-[13,14α-²H₂]kaur-15-ene (20), and three methoxy-substituted isomers of which ent-16-methoxy[²H₂]kaurane was the main component. Bridgehead enolisation of ent-17-nor[13,14α-²H₂]kauran-16-one (6) was demonstrated by oxidation of the ketone, before and after heating with potassium t-butoxide, to the lactones (23) and (25), respectively, in which the absence or presence of the 13-hydrogen atom was shown by the presence or otherwise of a one-proton multiplet at τ 5·22 in the n.m.r. spectra.

The mass spectra of some of the [²H₂]diterpenes, and the n.m.r. spectra of the ent-beyeran-15- and 16-ones (16) and (17) in the presence of the shift reagent Eu(dpm)₃, are discussed.