5- Cholesten-3-one

Fig. 1 Fluorescence scans of a blank (A) and of a mixture (B) of cholesterol (2), coprostanol (3), 4-cholesten-3-one (4), 5a-cholestan-3-one (5) and coprostanone (6), start (1), solvent front (7).

On a dark background cholesterol (Eluent A, h/ f 20-25) emitted blue, coprostanol (Eluent A, h/ f 25-30) blue, 4-cholesten-3-one (Eluent A, h/ f 40-45) blue, 5a-cholestan-3-one (Eluent A, h/ f 60) blue, coprostanone (Eluent A, h/ f 70) blue, estriol 3-sulfate (Eluent B, h/ f 5-10) yellow, 11-ketoetiocholanolone (Eluent B, h/ f 15-20) blue, estrone (Eluent B, h/ f 20-25) ochre, 11-desoxycorticosterone (Eluent B, h/ f 30-35) yellow, 17a-ethinyl-5-androstene-3p,17p-diol (Eluent B, hRj 45-50) ochre, 4-cholesten-3-one (Eluent B, h/ f 55-60) faint blue and coprostanone (Eluent B, h/ f 65-70) violet fluorescences. 

Fig. 1 Fluorescence scan of a chromatogram track with 255 ng cholesterol (1), 535 ng coprostanol (2), 310 ng 4-cholesten-3-one (3), 320 ng 5a-cholestan-3-one (4) and 220 ng coprostanone (5) per chromatogram zone.

Weakly fluorescent zones were visible under long-wavelength UV light (X = 365 i (Fig. 1). Cortisone (h/ f 0-5), dienestrol (h/ f 10-15), 4-androstene-3,17-dione (It 50-55) and 4-cholesten-3-one (h/ f 60-65) had an ochre fluorescence. Diethylsti estrol (h/ f 10-15), 17a-ethinyl-l,3,5-estratriene-3,17B-diol (h/ f 25-30) and estro (h/ f 35-40) had a blue emission. 

Fig. 2 Fiuorescence scan of a chromatogram track with 100 ng each of estriol-3-sulfate (1), 11-ketoetiocholanone (2), estrone (3) 11-desoxycorticosterone (4) and 17a-ethinyl-5 ndrostoi-3P,l 7P-diol (5), together with 1 pg each of 4-cholesten-3-one (6) and coprostanone (7) per chromatogram zone...

Another example of a nudibranch, which probably modifies dietary metabolites to obtain more effective allomones, is seen in Aldisa cooperi (= A. sanguinea cooperi) [155]. It elaborates two fish antifeedant bile acids (104,105) that are absent in its prey, the sponge Anthoarcuata graceae, where the main steroid is 4-cholesten-3-one (106). Biosynthetic experiments starting from both labelled mevalonic acid and labelled 4-eholesten-3-one would definitely clarify, whether, the two allomones (104-105) are biosynthetized de novo by the mollusc, or if they are derived from a food source. 

The earliest paper in this field used RuO from RuO /aq. Na(10 )/AcOH for cleavage of 4-cholesten-3-one and hexahydroindene to the corresponding carboxylic acids (Fig. 1.5) [195] minimal experimental data were given. An early example (1959) for RuOj/aq. Na(IO )/acetone involved oxidation of 3a-acetoxy-24,24-di-phenylchol-23-ene to 3a-acetoxynorcholanic acid [196],... 

In 3-oxosteroid A4-steroid 5)3-reductase deficiency, key intermediates for cholic and chenodeoxycholic synthesis, 7a-hydroxy-4-cholesten-3-one and 7a,12a-dihy-droxy-4-cholesten-3-one undergo side-chain oxidation and conjugation to produce... 

In work published in 1989, Hylemon et al. used cholesterol oxidase to convert 7a-hydroxycholesterol to 7a-hydroxy-4-cholesten-3-one. Cholesterol that remained was converted to 4-cholesten-3-one. 7/3-Cholesterol, which was added as an internal steroid recovery standard, was oxidized to 7/3-hydroxy-4-cholesten-3-one. These steroid products were analyzed by Qg reversed-phase chromatography on an Altex Ultrasil-ODS column (4.6 mm x 25 cm) using 70 30 (v/v) mixture of acetonitrile and methanol (Fig. 9.83). The eluate was monitored at 240 nm, and the amount of product determined from a calibration curve. 

Figure 9.83 Separation of 7a-hydroxy-4-cholesten-3-one (A), 7/3-hydroxy-4-cholesten-3-one (B), and 4-cholesten-3-one (C) by C-18 reveised-phase HPLC.

The second step in the synthesis of bile acids, according to Hylemon et al. (1991), is the conversion of 7a-hydroxycholesterol to 7a-hydroxy-4-cholesten-3-one by NAD+-dependent 3/3-hydroxy-A5-C27-steroid oxidoreductase. This enzyme is located in the endoplasmic reticulum of liver, and its catalysis of the 3/3-hydroxy group also results in isomerization of the double bond from A5 to A4. 

One milligram of microsomal protein is added to 0.1 M potassium phosphate buffer (pH 7.4) containing 50 mM NaF, 10 mM dithiothreitol, 1 mM EDTA, 20% glycerol (v/v), 150 iM 5-cholestene-3/3, 7a-diol, and 0.915% CHAPS. The reaction is initiated by 1 mM NAD+ to give a final reaction volume of 1.0 mL. After incubation at 37°C for 5 minutes, the reaction is terminated by adding 2 mL of 95% ethanol. An internal recovery standard, 4-cholesten-3-one (3 fig in methanol) is also added. The steroid products are extracted into 5 mL of petroleum ether (repeated twice). After the ether has been removed at 40°C under a stream of nitrogen, the products are dissolved in 100 fxL of mobile phase and 20 ju.L is injected into the column. The amount of product formed is linear with protein (to 1.5 mg) and with time (up to 10 min, 1 mg protein). The assay is much more sensitive than the direct spectrophotometric assay, and it avoids the use of thin-layer chromatography and radioisotopes described in other methods. 

Maruoka has successfully developed a highly accelerated Oppenauer oxidation [31,32] system using a bidentate aluminum catalyst [29]. This modified, catalytic system effectively oxidizes a variety of secondary alcohols to the corresponding ketones as shown in Sch. 9. For example, reaction of (2,7-dimethyl-l,8-biphenylene-dioxy)bis(dimethylaluminum) (8, 5 moI%) with carveol (14) at room temperature in the presence of 4-A molecular sieves, and subsequent treatment with pivalaldehyde (3 equiv.) at room temperature for 5 h yielded carvone (15) in 91 % yield. Under these oxidation conditions, cholesterol (16) was converted to 4-cholesten-3-one (17) in 75 % yield (91 % yield with 5 equiv. t-BuCHO). 

The air stable complex [RhCl(Py)2(DMF)(BH4)]Cl can hydrogenate a,p-unsaturated carbonyl compounds to saturated products. Methyl 3-phenylbutenoate (42) is converted to methyl 3-phenylbutanoate (43). 4-Cholesten-3-one, testosterone, 17-methyltestosterone and progesterone are also hydrogenated in good yields. - ... 

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