Further reactions of sideridiol [(–)-kaur-15-ene-7β,19-diol]

Abstract

The secondary hydroxy-group of sideridiol [(–)-kaur-15-ene-7β,19-diol](I) has been confirmed as being in the 7- rather than the 12-position. Bromination of methyl (–)-7-oxokauran-19-oate (IXb) gives methyl (–)-6β-bromo-7-oxokauran-19-oate (Xb); treatment of the latter with base gives (–)-7-oxokaur-5-en-19,6-olide (XII) mainly. Better yields of lactone (XII) are obtained by heating a solution of bromo-ester (Xb) in dimethyl sulphoxide under reflux. The n.m.r., o.r.d., and c.d. data for the bromo-ester (Xb) are discussed.