Cholanate

The ene reaction of an alkyne and an alkene produces a 1,4-diene. An important application, the regio- and stereoselective coupling of 17-(Z)-ethylidene steroids and alkynes to give cholane-type 16,22-dienes, is described in section 4.5.2. 

Cleavage of C-17 JilkylSubstituents. Resulting primarily in cholan-17-ones, this is a relatively minor metabohc pathway. Corticosterone is not known to... 

Huffman found that treatment of cholan-12-one (65b) with lithium and ammonia for 2 hours followed by addition of propanol gives 40 % of a pinacol together with 48.5 % of 12-ols in which the ratio of 12j5 12a is 19 1. This predominance of the 12 -ol was interpreted in terms of slow formation of a dianion of type (62) followed by its equilibration to the thermodynamically most stable configuration, i.e. one which affords the 12j5-ol upon protonation. An alternative explanation is that reduction in the presence of methanol involves protonation of a ketyl such as (61) by methanol, whereas in the absence of methanol reduction proceeds via the dianion (62) which is protonated on... 

From the preceding data it can be seen that reduction studies with NaBH4 have not been as extensive as those with Li AIH4. Reduction at the 4-position of the 5a-H series should give a predominance of the -epimer. Reduction of a 2-keto-3j -acetoxy compound gives 84% of the 2, 3)5-diol. ° In the 5J -H series reduction of 7-ketocholanic acid gives a 75% yield of 7a-hydroxy-cholanic acid with only traces of the 7 -ol, but 7-ketocholesterol gives a mixture of the 7a- and 7j8-epimers. ... 

The use of thiocyanic acid for thiirane synthesis is usually compatible with many functional groups found in natural steroids. The method has found application in androstanes, pregnanes, cholestanes, cholanates and cardeno-lides. However, the presence of a,j5-unsaturated carbonyl groups may decrease the yield of the thiocyanatohydrin due to conjugate addition of thiocyanic acid. Indeed, the 1,4-addition of thiocyanic acid has been carried... 

In the preparation of C-nor-D-homosteroid hormone analogs Mitsuhashi and Harada extended the Bamford-Stevens rearrangement to the cholanic acid series. Treatment of 3a-hydroxy-12-oxocholanic acid /j-toluene-... 

Fig. 2. Chemical structures of monensin (a) and cholanic acid (b). (Cited from Ref.8))...

Cholanic acid also possesses the ability of transporting cations across a lipophilic membrane but the selectivity is not observed because it contains no recognition sites for specific cations. In the basic region, monensin forms a lipophilic complex with Na+, which is the counter ion of the carboxylate, by taking a pseudo-cyclic structure based on the effective coordination of the polyether moiety. The lipophilic complex taken up in the liquid membrane is transferred to the active region by diffusion. In the acidic region, the sodium cation is released by the neutralization reaction. The cycle is completed by the reverse transport of the free carboxylic ionophore. 

The crude product is dissolved in benzene-hexane (1 1) and applied to a column containing 125 g. of silicic acid (Note 10). Elution with the same solvent gives traces (less than 5 mg. each) of the two fast-moving components in fractions 2 and 4 (125-ml. fractions) and chromatographically pure cholane-24-aI in fractions 5-8 (Note 11). Evaporation of the pooled fractions yields 870 mg. (84%) of the pure crystalline aldehyde, m.p. 102-104°. Recrystallization from 5 ml. of acetone raises the melting point to 103-104° (Note 12). 

The fractions were examined by thin-layer chromatography of 25-50 /J. aliquots as in Note 9. The checkers found that cholane-24-al is found in fractions 4-7. 

Cholane-24-al has not been previously synthesized by other methods. 

Cholane-24-ol, oxidation with dimethyl sulfoxide, dicyclohexylcarbo-di-imide, and pyridinium trifluoro-acetate, 47, 25... 

CYCLOBUTENE, 46, 34 Dicyclohexylcarbodiimide in oxidation of cholane-24-ol with dimethyl sulfoxide and pyridinium trifluor-oacetate, 47, 25... 

Das entsprechende 24-Butyl-(2)-oxy- oder 24-Butyloxy-5fi-cholan entsteht nur zu 41 bzw. 7% d.Th. 5a-Pregnan-20-5-carbonsaure-tert.-butylester wird zu 20-S-tert.-Butyl-oxymethyl-5oc-pregnan (68% d.Th. F 121-122°) reduziert. 

Studies on the Antibacterial Properties of the Bile Acids and Some Compounds Derived from Cholanic Acid, M. Stacey and M. Webb, Proc. R. Soc., Ser. B, 134 (1947) 523-537. 

The 3,12-diacetoxy-wor-cholanic acid may be purified by crystallization from acetone. It melts at 207-208°. 

The solid crystalline cake (Note 2) is dissolved in about 400 ml. of ether and extracted with 500 ml. of 2.5% potassium hydroxide solution (Note 3). The alkaline solution is immediately acidified with 200 ml. of 10% hydrochloric acid, and the crude 3,12-diacetoxy-raor-cholanic acid (Note 4) is collected on a filter. 

Park JH, Kwona S, Nam JO et al (2004) Self-assembled nanoparticles based on glycol chitosan bearing 5h-cholanic acid for RGD peptide delivery. J Control Release 95 579-588... 

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