Biosynthesis of terpenes and steroids. Part IX. The sterols of some mutant yeasts and their relationship to the biosynthesis of ergosterol

Abstract

The sterols of four mutant strains of Saccharomyces cerevisiae have been isolated and characterised and the mutations have been related to the pathway for ergosterol biosynthesis. The effects of the mutations are to block, respectively, the introduction of the side chain methyl group, the introduction of the 5,6- and 22,23-double bonds, and the Δ8→Δ7 isomerisation. The following sterols previously unreported in yeast have been isolated and characterised: cholesta-5,7,24-trien-3β-ol (2; R = H), ergost-8-en-3β-ol, ergosta-8,22-dien-3β-ol (5; R = H), ergosta-5,8,22-trien-3β-ol (6; R = H), and ergosta-5,7-dien-3β-ol. Cholesta-5,7,22,24-tetraen-3β-ol, ergosta-8,22,24(28)-trien-3β-ol, and ergosta-8,14,24(28)-trien-3β-ol, which were previously unknown, have also been isolated and characterised.