Ergosterol esters

Chaibakhsh, N Basri, M Rahman, MBA Adnani, A Salleh AB. Lipase-catalyzed sysnthesis of ergosterol ester. Biocatalysts and Agricultural Biotechnology, 2012, v. 1 (51-56), 2012. 

Two endoperoxides, 351 and 352, were obtained from optically active a-phellandrene (550),242,243 indicating that no steric hindrance is exerted by the isopropyl group of 350 on an oxygen attack. Stereoselective oxygenation is observed with ergosterol (555),19,22,23 lumisteryl acetate (555),244 levopimaric acid (557),245,246 and the benzoic ester of 6/3-hydroxy-5,5,9-trimethylhexahydronaphthalene (360),247 to mention... 

Protection of steroidal 5,7-dienes (3, 223-224 6, 467 9, 372). The adducts of 1 with an ester of ergosterol can be obtained in >90% yield by reaction with 1 prepared in situ. The diene system can be regenerated by treatment with 2 N KOH in 95% ethanol. The derivative prepared from 2 is particularly readily hydrolyzed (98% yield), and consequently this reagent is generally preferable to 1. ... 

Volatile fatty acids are by-products in the formation of long-chain fatty acids, which are required for cell membrane phospholipid biosynthesis. The biosynthesis of volatile fatty acids is generally controlled by the same factors that control the formation of ethyl fatty acid esters, that is, oxygen, ergosterol and various insoluble solids (grape solids, clarification solids, yeast hulls) tends to suppress production whereas sugar concentration and clarification are stimulatory (Bardi et al. 1999 Delfini et al. 1992, 1993 Edwards et al. 1990 Houtman et al. 1980). 

Alumina for esterification. A simple and rapid method of esterification which is particularly convenient for working on a scale of 20 mg. to 20 g. is as follows. An alcohol, for example ergosterol, is treated in benzene solution with a slight excess of benzoyl chloride or p-phenylazobenzoyl chloride and 2 equivalents of pyridine. When the reaction is complete, filtration through a small column of alumina (activity II, Woelm E. Merck) gives a solution of the desired ester in pyridine. After evaporation of the benzene, pyridine is removed by addition of toluene and evacuation on the steam bath. 

FIGURE 18-6 Chemical structures of major sterols and cholesterol derivatives. The major sterols in animals (cholesterol), fungi (ergosterol), and plants (stigmasterol) differ slightly in structure, but all serve as key components of cellular membranes. Cholesterol is stored as cholesteryl esters in which a fatty acyl chain (R = hydrocarbon portion of fatty acid) is esterified to the hydroxyl group. Excess cholesterol is converted by liver cells into bile acids (e.g., deoxycholic acid), which are secreted into the bile. Specialized endocrine cells synthesize steroid hormones (e.g., testosterone) from cholesterol, and photochemical and enzymatic reactions in the skin and kidneys produce vitamin D. 

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