Cholesteryl bromide

Lithium bromide-Boron trifluoride etherate. Aliphatic ethers can be cleaved by reaction with lithium bromide and boron trifluoride etherate in acetic anhydride at room temperature for 30 hrs. Methoxycyclohexane, for example, is converted into a 7 1 mixture of acetoxycyclohexane and cyclohexene. Saturated steroid ethers are cleaved to mixtures of enes and acetates under these conditions choles-teryl methyl ether gave about equal parts of cholesteryl acetate and cholesteryl bromide. However, Narayanan reports that the lithium halide is not essential and indeed often detrimental. Thus cholesteryl methyl ether treated with boron trifluoride etherate and acetic anhydride in ether at 0° (14 hrs.) gave cholesteryl acetate in 93% yield. 

In the 1960s, there was already a forerunner of photochemically induced phase transition in LC (20). When mixtures of cholesteryl iodide and cholesteryl bromide with cholesteryl nonanoate were exposed to UV irradiation, the helical pitch of cholesteric LC changes as a result of photodecomposition of the halides. The reflected color shifts gradually to red with progression of photodecomposition. Pattern-wise imaging was demonstrated but the image was blurred within 15 min. since LC of small molecules is a viscous fluid. 

A preliminary report" states that reaction of cholesteryl benzoate with (-butyl hydroperoxide and a catalytic amount of cuprous bromide in benzene gave equal parts of A -cholestene-3, 7a- and -3, 7j8-diol dibenzoate. Here allylic attack is not attended with rearrangement. 

Kunieda s group reported numerous viscoelastic worm-like micellar systems in the salt-free condition when a lipophilic nonionic surfactant such as short hydrophilic chain poly(oxyethylene) alkyl ether, C EOni, or N-hydroxyethyl-N-methylaUcanolamide, NMEA-n, was added to the dilute micellar solution of hydrophilic cationic (dodecyltrimethylammonium bromide, DTAB and hexade-cyltrimethylammonium bromide, CTAB) [12-14], anionic (sodium dodecyl sulfate, SDS [15, 16], sodium dodecyl trioxyethylene sulfate, SDES [17], and Gemini-type [18]) or nonionic (sucrose alkanoates, C SE [9, 19], polyoxyethylene cholesteryl ethers, ChEO [10, 20], polyoxyethylene phytosterol, PhyEO [11, 21] and polyoxyethylene sorbitan monooleate, Tween-80 [22]) surfactants. The mechanism of formation of these worm-Hke stmctures and the resulting rheological behavior of micellar solutions is discussed in this section based in some actual published and unpublished results, but conclusions can qualitatively be extended to aU the systems studied by Kunieda s group. 

Ceteth-24 Ceteth-25 Ceteth-45 Ceteth-80 Ceteth-10 phosphate Cetethyidimonium bromide Cetethyl morpholinium ethosulfate Cetoleth-6 Cetoleth-15 Cetoleth-24 Cetoleth-25 Cetrimonium tosylate Cetyl betaine Cetyl PPG-2 isodeceth-7 carboxylate Cetylpyridinium chloride Cholesteryl/behenyl/octyidodecyl lauroyl glutamate Cholesteryl oleate Choleth-15 Cocamide Cocamide DEA Cocamide MEA Cocamide MIPA Cocamidoethyl betaine ... 

Syntheses of 1,2-orthoesters of 4,6-0-benzylidene-a-D-galactopyranose have been reported. 1,2-Orthoesters of D-glucopyranose and several steroid or triterpenoid alcohols have been prepared via acetylated glycosyl nitrates e.g, 3,4,6-tri-O-acetyl-a-D-glucopyranose l,2-(cholesteryl orthoacetate) was obtained when a mixture of cholesterol, 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide,... 

The reaction of alkyl bromides with alcohols to form ethers, promoted by silver salts of dicarboxylic acids, the Koenigs-Knorr synthesis, is sometimes complicated by the recovery of the ether from the dicarboxylic acid. A copolymer network of maleic acid and l,4-bis(vinyloxy)butane was transformed into the silver salt (41) and used for the reaction of 2,3,4,6-tetra-O-acetyl-la-bromoglucopyranose with cholesterol to give the cholesteryl ether in 55% yield as shown in Scheme The polymeric by-product dicarboxylic acid was filtered easily from the product solution. 

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