48 SOME ASPECTS OF YEAST STEROL BIOSYNTHESIS

概要

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As part of a general programme for the investigation of yeast sterol biosynthesis, the synthesis and biosynthesis of ergosta-5,7,22,24(28)-tetraen-3β-ol(IIa) were carried out. Ergosteryl acetate(Ib) was converted to the 1,4-adduct(IVa) with 4-phenyl-1,2,4-triazoline-3,5-dione(III). Reaction conditions of retro-1,4-cycloaddition and ozonolysis of the 1,4-adduct to the aldehyde(V) were investigated. Ethyl 2-isopropyl acrylate(VIIa), which was prepared from the half-ester(VI) and formalin, was successively treated with a mixture of lithium aluminium hydride and aluminium chloride, phosphorus tribromide, and triphenyl phosphine to give the phosphonium salt(VIId). Condensation of the aldehyde(Va) with the phosphorane(VIIe) prepared from the phosphonium salt(VIId) afforded the Wittig product(VIII), which on reduction with lithium aluminium hydride gave the desired tetraene(IIa). The radioactive tetraene(23,28-^<14>C-II) was prepared from ^<14>C-paraform essentially in the same manner as above. The radioactive ergosterol(4,4-^3H-I) was also obtained from the enol acetate(IX) by sodium borohydride reduction in the presence of tritiated water. Biosynthetic experiments of these radioactive sterols(23,28-^<14>C-II and 4,4-^3H-I) to yeast revealed that ergosterol(Ia) is biosynthesised from the tetraene(IIa) but there is no equilibrium between ergosterol(Ia) and the tetraene(IIa).
天然有機化合物討論会の論文
1970-10-01