Bile acid based ketone

In 2001, Bortolini, Fogagnolo, and coworkers reported the epoxidation of cinnamic acid derivatives using bile acid based ketones [93, 94]. As shown in Scheme 3.57, up to 95 % ee was obtained for p-methylcinnamic acid with ketone 77a [94]. Studies with various ketone analogues showed that the epoxidation could be significantly influenced by the substituents at C-7 and C-12 of the bile acid [94]. 

The strong-base anion-exchange paper has been employed (38) in the hydroxide form for the separation of free and taurine-conjugated bile acids with diisobutyl ketone-acetic acid-water (4 5 1, v/v/v) or chloroform-methanol-ammonia (4 1 0.1, v/v/v) as developing solvents. It would be anticipated that these systems would also be capable of resolving glycine-and taurine-conjugated bile acids. 

Spectra of O-methyloximes of methyl 3,6-diketo-5a- and 3,6-diketo-5/3-cholanoates have been reported by Allen et al. (30). The O-methyloximes, prepared as described by Fales and Luukkainen (49), were found to be particularly useful derivatives since the 5a- and 5 -isomers could be separated by gas chromatography, which was not the case with the free ketones. Considerable differences in relative intensities of the peaks were noted between the spectra of the two isomers. The 5y3 compound gave a base peak at mje 138 (probably ring A) whereas the molecular ion was base peak in the spectrum of the 5a-epimer. These results show the value of O-methyloximes in mass spectrometry of ketonic bile acids. It should be recognized that partial derivative formation may occur, and that formation of syn- and o //-isomers may result in a complex mixture of products from a pure compound. 

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