19-cholesteryl methyl

Cholestanyl methyl ether has been prepared by catalytic hydrogenation of cholesteryl methyl ether 7 and of cholest-4-en-... 

Solv. Ref. C- Cholesteryl acetate Dioxane/CHCl3 [65 a] Cholesteryl methyl ether Dioxane/CHCl3 [65 a] 7-Dehydro- cholesteryl acetate Dioxane/CHCl3 [65 a] Ergostcrol Dioxane/CHCl3 [65 a] Lanosterol CDC13 [587] Dihydro- lanosterol CDC13 [587]... 

The concept of a stable mesomeric cation cannot be inferred solely from kinetic results, but follows from analysis of reaction products, and studies of the reactions of "i-cholesterol and its derivatives. Most important was the demonstration by Winstein [35] that identical product mixtures are produced by the methanolysis of either cholesteryl tosylate or 6 trichloroacetoxy-3a,5a-cyclocholestane (15 X O-COCCls), from which it was argued that these steroids solvolyse through a common cation. Furthermore i-cholesteryl methyl ether (15 X = OMe) is converted by absolute ethanol into a mixture of i-cholesteryl ethyl ether (15 X — OEt) and cholesteryl ethyl ether [36]. i-Cholesteryl acetate (15 ... 

Etherification, When cholesterol (1) is heated for several hours in dimethyl phosphite, cholesteryl methyl phosphite (2) is obtained as the main product. However, if/>-TsOH is present, 3/S-mcihoxy-A -cholestene (3) is obtained as the main product in about 60 % yield. Cholestanol is converted by this method into 3/S-methoxycholestanc in 60-70% yield. 

Cholesteryl methyl ether is converted into 3)8-chloro- or 3) -bromo-cholest-5-ene by the appropriate phosphorus pentahalide in the presence of boron trifluoride etherate. ... 

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. 

However, Narayanan and Iyer found that cleavage can be effected with boron trifluoride and acetic anhydride alone and that a lithium halide slows down the reaction and does not decrease elimination to the olefin. They obtained cholesteryl acetate from cholesteryl methyl ether (homoallylic) in 93% yield (15 hrs, at 0°). Cleavage of an allylic methyl ether (A -cholestene-3y3-ol methyl ether) required only 3 min. at —18° (90% yield) under less mild conditions the main product was the A Miene. Cleavage of saturated ethers was attended with considerable elimination. R. D. Youssefyeh and Y. Mazur, Tetrahedron Letters, 1287 (1962)... 

If there is no /J-hydrogen atom in the alkyl group R, as is the case with cholesteryl methyl or benzyl ether, then cholestadiene is the sole product. According... 

Cholesterol, heated in dimethyl phosphite, alfords cholesteryl methyl phosphite (128), but in the presence of an acid the product is cholesteryl methyl ether. 

The rearrangement of 3a(,5-cyclo-5o -cholestan-6 -ol (681) under irradiation in benzene-methanol was recently reported to give a mixture of the methyl ether (682) and cholesteryl methyl ether (683). Further study has shown that the reaction is a normal acid-catalysed one, apparently induced by an initial photochemical oxidation of methanol. The cyclosteroid is stable under irradiation in degassed solutions, which preclude oxidation. 

Fig. 3 Effect of cholesteryl ethers in liposomes prepared with DOPC on the relative amount of glucose released (A) (x) cholesterol (o) cholesteryl methyl ether ( ) cholesteryl ethyl ether (v) cholesteryl-n-propyl ether ( ) cholesteryl isopropyl ether (A) cholesteryl butyl ether (B) (x) cholesterol (o) cholesteryl (2 -hydroxy)-3-ethyl ether ( ) cholesteryl methoxy methyl ether ( ) cholesteryl acetate.

A major problem with the sulfoxide synthesis using menthyl sulfmates is its failure to produce optically pure dialkyl sulfoxides. The prerequisite menthyl alkanesulfinates are oils which have resisted separation into the individual epimers. The menthyl phenyl methanesulfmates are an exception the R epimer is crystalline . One solution to this problem, at least for preparing methyl alkyl sulfoxides, was achieved using cholesteryl methanesulfmates (27) . Both epimers were crystalline and could be separated by fractional crystallization, although in poor yield. Treatment of the epimers with n-propyl, n-butyl, isobutyl, p-tolyl and benzyl magnesium halides yielded the respective methyl alkyl sulfoxides (28) in greater than 95% e.e. and in 32 to 53% yields. 

Ru(CO)(den-por) (den-por=dendritic porphyrins). These are made by condensation of Ru(CO)L (L=5,10,15,20-tetrato(4 -hydroxyphenyl)porphyrin or 5,10,15,20-tetrakis(3, 5 -dihydroxy-phenyl)porphyrin), themselves made from RUjlCO) and (L), with poly-(benzylether) dendrons H, C NMR, electronic and IR spectra of the products were measured. Epoxidation of cyclic alkenes, cis- and tranx-sfilbene, styrene and its 3-methyl, methoxy, chloro and bromo derivatives, dimethylchromene and of cholesteryl esters in high yields and turnovers was effected by RulCOKden-porl/lCl pyNOl/CHjClj [871]. 

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