Rabbit 3-hydroxyhexobarbital dehydrogenase is a NADPH-preferring reductase with broad substrate specificity for ketosteroids, prostaglandin D2, and other endogenous and xenobiotic carbonyl compounds
for NADP(H) over NAD(H) at a physiological pH of 7.4. In the NADPH-linked reduction, 3HBD showed broad substrate specificity for a variety of quinones, ketones and aldehydes, including 3-, 17- and 20-ketosteroids and prostaglandin D(2), which were converted to 3alpha-, 17beta- and 20alpha-hydroxysteroids and 9alpha,11beta-prostaglandin F(2), respectively. Especially, alpha-diketones (such as isatin
Diethylhydrogensilyl cyclic diethylsilylene derivatives in gas chromatography-mass spectrometry of hydroxylated steroids. II. Pregnanes with a hydroxylated 17.BETA.-side-chain.
The gas chromatographic-mass spectrometric properties of diethylhydrogensilyl cyclic diethylsilylene derivatives of hydroxypregnanes were studied. Pregnanes with a sterically hindered 11β-hydroxyl group were smoothly silylated with a new silylating agent, N, O-bis(diethylhydrogensilyl)-trifluoroacetamide, under mild conditions. The mass spectra of these derivatives were characterized by the appearance of the intense molecular ion peak, which provides convenient and reliable confirmation of the molecular weight of these hydroxypregnanes. The most characteristic fragment ions were those at m/z 185 for 17, 20-diols and at m/z 287 for 17, 20, 21-triols, which were produced by cleavage at the C(13)-C(17) and C(15)-C(16) bonds with hydrogen atom transfer. This indicates that all of the major fragmentations are directed by the cyclic diethylsilylene group. Another fragmentation common to the spectra was the successive loss of diethylhydrogensilanol from the molecular ion. A remarkable difference in the appearance of peaks was observed between DEHS-DES derivatives of a 17α, 20α, 21-triol and its 20β-isomer. Structures are proposed for some of these fragment ions.