5o-Cholestan

Addition of fluorine to double bonds preparation of 3 -chloro-5, 6a-difluoro-5o -cholestane by addition of fluorine, 453... 

Ligand 92 was readily prepared by reaction of (+)-pinocarvone with 1-phenacylpyridinium iodide. The authors similarly prepared corresponding 5,6-dihydro-1,10-phenanthrolines derived from (+)-pinocarvone and a tetrahydroquinolone (structure 93, [127]) and obtained up to 81% in the palladium-catalyzed test reaction. Chelucci et al. [ 128] reported the synthesis of chiral Ci-symmetric 1,10-phenanthrolines incorporated in asteroid backbone. Structure 94 derived from 5o -cholestan-4-one in Scheme 51, allowed very high yield and up to 96% ee using BSA and tetrabutylammonium fluoride to generate the malonate anion. 

A mixture of EtsSiH/TFA in dichloromethane reduces 3-methyl-5-a-cholest-2-ene to give the pure equatorial methyl isomeric product, 3/3-methyl-5o -cholestane, in 66% yield (Eq. 79).126 On the other hand, attempts to reduce cholest-5-ene using the same technique yield neither 5a-cholestane nor 5/3-cholestane, but instead an isomeric mixture of rearranged olefins. This result is presumably because of the inability of hydride attack to compete with carbocation skeletal isomerization and elimination.126... 

In ethanol 2,4-dinitro-5o -cholestan-3-one, 261, exists entirely as the enol, which is irradiated to give a mixture of diosphenols, 262, and its isomer, 263, in 55% yield (equation 117)136. Similarly, photolysis of an equilibrium mixture of 264 and 265 gives 266 in 48% yield (equation 118). 

Steroidal Alkaloids. Photolysis of (22S 25S)-N-chloro-22,26-imino-5os-cholestan-3P-ol and the corresponding l6p-hydroxy substituted (22S 25R)-> (22S 25S)-, and (22-S 23R)-N-chloro compounds caused fragmentation to a mixture of the corresponding 20R and 20S chloropregnane derivatives. Whereas photolysis of (22R 25S)-N-chloro-22,26-imino-50-cholestan-5P-ol gave the corresponding Ib-chloro derivative. " UV-irradiation of the stereoisomeric N-nitroso-22,26-iminocholestane-3P,l6p-diols in acidic solution led to the corresponding spirosolane alkaloids soladulcidine,. solasodine, and tomatidine respectively, by way of the intermediate... 

In a similar study, Nerbonne and Weiss (25) found that photodimerization of acenaphthylene proceeds 10 times more efficiently in the cholesteric than in the isotropic phase of a 1/1 (w/w) mixture of 5o-cholestan-3j8-yl nonanoate/Sa-cholestan-... 

Selective removal of bromine from 3/3,5,6/3-tribromo-5a-cholestane to give 3/3-bromocholest-5-ene was achieved by reaction with [T -C5H5Cr(N02)2]2. The reactions of 11/3-hydroxy-steroids with dialkylaminosulphur trifluorides depend on the substitution at C-9 and involve the formation of intermediate (11) (Scheme 1) (see ref. 232). Selective dehydration with FeCls adsorbed on silica gel allowed the conversion of 5a-cholestane-3/3,5-diol into cholesterol (80%) and 3i3-acetoxy-5a-cholestane-5,25-diol into 3/S-acetoxycholest-5-en-25-ol (72%). Other examples and additionally the hydrolysis of 5,6a-epoxy-5o -cholestan-3/3-ol to the 3/3,5a,6/8-triol (90%) were reported. Chromatographic alumina is reported to effect smooth elimination of sulphonic acids from the esters with less than normal rearrangement. Thus lanosteryl tosylate and cycloartenyl tosylate gave the respective A -compounds in yields of 90% and 45% respec-... 

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. 

CAS 80-97-7 EINECS/ELINCS 201-315-8 Synonyms Cholestanol Cholestan-3-ol Cholestan-3-ol, (3p,5o)- Cholestan-3p-ol 5a-Cholestanol... 

Sterols and Related Products - The Westphalen rearrangement of some JP-substituted-bp-acetoxy-5Q -hydroxycholestanes has been studied and the products and kinetics shown to be dependent on the nature of the 5-substituent. The conformations of the products were studied and in the case of the Westphalen-Lettre derivatives it was shown that ring B is in the boat conformation. The boron trifluoride catalyzed cleavage of 30 -acetoxy-4a,5-epoxy-5Ci -cholestane afforded the expected backbone rearrangement products containing a 15(17) doable bond." A similar experiment with 5Q -acetoxy-5,ba-epoxy-5o -cholestane yielded some of the rearranged derivative XW after a reaction time of 25 seconds, along with the e q)ected isomer " ... 

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