The meliacins (limonoids): minor constituents of Khaya anthotheca: reduction of the meliacins with zinc–copper couple

Abstract

The residues collected after isolation of anthothecol from Khaya anthotheca have afforded a new meliacin for which the structure (2b)(11β-acetoxyazadirone) is proposed. In addition, deacetylanthothecol and a sterol mixture shown by g.l.c. to consist of stigmasterol, β-sitosterol, campesterol, cycloeucalenol, and 24-methylenecycloartanol, were isolated. In the course of model experiments with anthothecol aimed at structural correlation with the new compound, zinc–copper couple was found to be a convenient and superior reagent for reduction of epoxides to olefins, αβ-unsaturated ketones to saturated ketones, and ketols and their acetates to ketones, in the meliacin series. By using this reagent new reduction products of anthothecol have been prepared and characterised.