Terpenoids. Part III. The enolisation–ketonisation and optical rotatory dispersion of the ent-kauran-15-ones and 13β-kauran-15-ones

Abstract

At temperatures below 100° the rates of enolisation of the 16R-epimers of ent-kauran-15-one and 13β-kauran-15-one are much greater than those of the 16S-epimers, and the enols are exclusively ketonised to the 16R-epimers. Reasons for this kinetic control are discussed in terms of steric hindrance, torsional strain, and stereoelectronic factors. The conformation of these ketones is also discussed in terms of their o.r.d. and c.d. properties.