Studies on the Biosynthesis of the ergosterol side chain

Abstract

1. A convenient synthesis of 24-methylene[23,25-(3)H(3)]dihydrolanosterol is described. 2. A general anaerobic-aerobic method for the incorporation of sterols into whole yeast cells is also described and illustrated by experiments with (3)H-labelled lanosterol. 3. The method was used to convert labelled 24-methylene-dihydrolanosterol into ergosterol, in good yield, by Saccharomyces cerevisiae. 4. Degradation of the biosynthetic ergosterol provided confirmation of the conversion, which supports the proposed mechanism for the biosynthesis of the ergosterol side chain. 5. Mechanisms for the further conversion of the 24-methylene side chain into the ergosterol side chain are discussed and it was shown that a compound, [3alpha-(3)H(1)]-ergost-7-en-3beta-ol, with a fully saturated side chain, can also be efficiently incorporated into ergosterol. 6. This result was confirmed by a procedure involving formation of the 5,8-epidioxide and subsequently the 5,8-epidioxy-22,23-epoxide of the biosynthetic ergosterol.

The stereochemistry of hydrogen elimination from C-7 in cholesterol and ergosterol biosynthesis

“…Preparation of 3fi-acetoxy-5a,8a-epidioxyergo8ta-6,22diene (V). This was prepared by the method of Akhtar, Parvez & Hunt (1969).…”

Effect of Altered Sterol Composition on Growth Characteristics of Saccharomyces cerevisiae

“…The synthesis, distribution, and function of sterol lipids in yeast has been an area of intensive investigation for many years. The bulk of the research effort has been devoted to elucidating the pathway of sterol synthesis, with many investigators suggesting intermediates and alternate routes for the formation of ergosterol (3,5,12,15,19,20,30). Although unanimity among authors on the respective position and importance of many of these intermediates in the pathway has not been attained, there is reasonable agreement for the general pathway shown in Fig.…”

Studies in Phytosterol Biosynthesis: Observations on the Biosynthesis of Fucosterol in the Marine Brown Alga Fucus spiralis

“…The loss of tritium therefore demonstrates the location of one tritium atom a t C-25 of the fucosteryl acetate and proves the migration of the hydrogen (or tritium in this case) from C-24 to C-25 during the biosynthetic alkylation reaction as predicted by theory [5]. This hydrogen migration has also been demonstrated to occur in the C-24 alkylation reaction involved in ergosterol biosynthesis by yeast [26] and poriferasterol biosynthesis in Ochromonas malhamensis [27]. A similar hydrogen migration has also been observed during tuberculostearic acid biosynthesis [28j.…”