Steroid oximes

Mouse lanosterol 14a-Me demethylase (P 450DM) A steroidal oxime that inhibits cholesterol biosynthesis 126... 

Two features about steroid oximes should be mentioned since they impact quantification firstly, an 11-carbonyl group is sterically hindered and not derivatized, so steroids containing this moiety have a mass 29 units less than expected. Secondly, each carbonyl can be derivatized two stereospecific ways, termed syn- and anti- . These may or may not be resolved by GC. If they are resolved it is preferable to determine the area of both peaks since the relative amount of syn- and anti- forms may vary between different derivatizations. 

Fragmentations may be governed by steieoelectronic factors.The steroidal oxime (52 equation 34) fragmented with loss of a deuteron from the 4a-methyl group, whereas the analog (53 equation 35) fragmented with proton abstraction from the 43-methyl group. - ... 

Low-valent metal salts have been used to bring about reductive cleavage of oximes. Corey and Rich-man used chromium(II) acetate to convert O-acetyl ketoximes into imines, which were hydrolyzed to ketones. " Aqueous titanium(III) chloride and vanadium(II) salts also reduce oximes again, the imines are usually hydrolyzed in situ, but some hindered imines, such as compound (37), are isolable." A method of preventing hydrolysis is to carry out the reduction in anhydrous conditions in the presence of an acylating agent. The products of such reactions, when applied to oximes of enolizable ketones, are en-amides. For example, these ketoximes are converted into A/-formylenamines when heated in acetonitrile with anhydrous titanium(III) acetate and acetic formic anhydride cyclohexanone oxime gives the en-amide (38 97% Scheme 22)." This type of reduction has been used by Barton and coworkers to prepare enamides from steroidal oximes. They reported that the reaction could be performed by acetic... 

Examples of steroid oximes hydrogenated in a similar manner are given in Table 5. 

The mass spectral fragmentations of backbone-rearranged steroids of the type (60) and the related A " -olefins are characteristic and dependent upon the configuration of the side-chain. Mass spectral fragmentation patterns are reported for a number of steroidal oximes, and for 5a-chloro-6j5-nitro-steroids, for a series of 22,26-epiminocholestane derivatives, and for 5a- and 5j5-3,6-diones. The mass spectrometry of cardenolides has been reviewed. ... 

Cleavage of oximes and semicarbazones. Steroidal oximes and semicarba-zones are cleaved in high yield by TiCla in buffered dioxane solution (pH 6). Oximes are cleaved at room temperature steam-bath temperatures are preferred for semicarbazones. 

Shafiullah and Ansari " found the steroidal oximes 320 to be useful starting materials for preparing the steroidal oxazoles 322 (Scheme 1.87). The authors also isolated small amounts of the corresponding ketones 323. 

CD of various steroids ond reloted compounds W1 and of steroidal oximes l/. C2o configuration of steroids... 

In other publications, the TLC of iminocholestanes [1] and steroid oximes [66, 102] has been treated the customary solvents, if necessary with added acetic acid, were used. 

Kovganko, N.B. and Chernov, Y.G. (2000) Novel synthesis of (24R,6 )-24-ethylcholest-6-hydroxyimino-4-en-3-one, a steroidal oxime from Cinachyrella spp. sponges. Chem. Nat. Compd. (Eng. Trans.), 36,189-191. 

Cui, J., Fan, L Huang, Y, Xin, Y, and Zhou, A. (2009) Synthesis and evaluation of some steroidal oximes as cytotoxic agents Structure/ activity studies (11). Steroids, 74,989-995. 

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. 

Table 11 Lipase-Mediated Diastereoselective Hydrolysis of Steroidal Oxime Methyl Esters ...

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