Steroids geometrical isomers

Separations involving cis/trans isomers can also be accomplished by employing NPC. An example of this application is the separation of tricyclic antidepressant doxepin, which is marketed as a mixture of geometric isomers in a cis/trans ratio of 15 85 [41], When a spherisorb silica column is used with a hexane-methanol-nonylamine mobile-phase system, the cis isomer of doxepin elutes first. The structures of the two isomers and the chromatographic separation are shown in Figure 5-7. NPC has also been successfully employed in the separation of cis/trans isomers of steroids. Four diastereomers... 

A stereoselective tandem Sakurai-carbonyl-ene reaction for the synthesis of steroid derivatives has been reported [48]. When LtAlCl2 and la were employed in this cyclization, stereochemical control was different. The cyclization product obtained with la is only 19 (Sch. 17), even though the starting material contained all four geometrical isomers use of LtAlCl2 resulted in a mixture of two different stereoisomers in lower yield. 

Facile geometric isomerization of phenolic non-steroidal estrogens and antiestrogens limitations to the interpretation of experiments characterizing the activity of individual isomers. Journal of Steroid Biochemistry, 22, 589-596. 

Geometrical isomeric mixtures of steroidal oxime esters have been evaluated for the enzymatic transformations. In this respect, the work by Adamczyk and co-workers [27] describes the use of lipase from CCL in the diastereoselective hydrolysis of 3-(0-carbox-ymethyl)oxime methyl esters, 17a-hydroxyprogesterone 122, progesterone 124, testosterone 126, and cortisol 128. CCL proved to be effective in carrying out hydrolysis of methyl esters of steroidal 3-carboxymethyl oximes in a mild manner affording the E and Z dia-stereoisomers 123/122, 125/124, 127/126, and 129/128 in different ratios. The enzyme exhibited a preference for the anti isomer (Table 11). The faster rate and greater selectivity observed for 128 is probably due to the cortisol derivative s better solubility in the reaction media. 

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