Petroleum fraction, benzene-eluted

Elution with a petroleum ether-benzene (1 1) mixture (2.2 liters) affords 5.8 g of starting material. Further elution with petroleum ether-benzene (1 1) (400 ml) gives initially 0.57 g of a mixed fraction, followed by 0.47 g of a crude product (eluted with another 400 ml of the same solvent mixture). Crystallization of the latter fraction from methylene dichloride-petroleum ether gives (20 R)-18,20-cyclo-5a-pregnane-3/5,20-diol 3-acetate mp 164-166.5° [ ]q 9°. Elution with benzene (400 ml) gives 1.57 g of an oil. Continued elution with benzene (600 ml) and benzene-ether (9 1) (800 ml) provides 1.81 g of crude (20 S)-18,20-cyclo-5a-pregnane-3j9,20-diol 3-acetate mp 139-140° [a]o 15°. 

This oil is dissolved in benzene (100 cc) and chromatographed through silica (430 g). After elution with ethyl acetate, there is collected a fraction of 21 liters, which is concentrated to dryness under reduced pressure (20 mm Hg). The crystalline residue (32.5 g) is recrystallized from acetonitrile (100 cc) and a product (16.4 g), MP 94°C, is obtained. On recrystallization from a mixture of benzene (60 cc) and petroleum ether (200 cc), there is finally obtained 2-(3-benzoylphenyl)propionic acid (13.5 g), MP 94°C. 

A solution of 9-phenyl-9//-purine-6-carbonitrile (0.2 g. 0.9 mmol) and N,.V-dielhylprop-l-ynamine (0.2 g, 1.8 mmol) in xylene (3 mL) was refluxed for 18 h. After cooling, the mixture was poured into excess H20, and extracted with CHC13. The extract was washed with H20, dried (Na2S04), and concentrated to dryness. The residue was chromatographed (silica gel, CHCl, then benzene/ EtOAc 20 1). The fraction eluted with benzene/ EtOAc gave the product [yield 194 mg (65 %)] as pale yellow needles after recrystallization (benz-cnc/petroleum ether) mp 157— 158 C. 

A solution of 0.22 g of 17a-methyl-androstane-4p,5a,17p-triol-3-one in 100 ml of methanol is allowed to stand at room temperature for 22 h, under nitrogen, with 0.30 g of potassium hydroxide in 4 ml of water and 20 ml of methanol. The solution is then neutralized with acetic acid, concentrated in vacuo, diluted with water and extracted three times with ethyl acetate. The extract is washed with water and the solvent removed by distillation. The remaining residue is chromatographed over Florisil 30-60 mesh. The fractions eluted with benzene and benzene-ether (10 1) are combined and by crystallization from ether-petroleum ether give 4-hydroxy-17a-methyltestosterone (0.120 g) melting at 168°-170°C. 

A solution of 1.04 g of 6-chloro-9p,10a-pregna-4,6-diene-3,20-dione and 0.95 g of 2,3-dichlorobenzoquinone in 50 ml of dry benzene was heated to reflux for 10 hours. The reaction mixture was diluted with 70 ml of benzene and extracted three times with 50 ml of 2 N sodium hydroxide solution. The benzene layer was washed with water to neutral, dried with sodium sulfate and evaporated to dryness. The residue (0.7 g) was chromatographed on 20 g Of aluminum oxide (activity II). The fraction eluted with benzene-petroleum ether were combined and recrystallized from acetone. The 6-chloro-9p,10a-pregna-l,4,6-triene-3,20-dione melted at 208-209°C(decomposition), Xmax 229 nm. 

Iodo-4-penten-l-yl 11-Methoxycarbonylundecyl Tellurium (Sodium Borohydride Reduction) Into an argon-purged, 100-m/ flask are placed a magnetic stirrer, 343 mg (0.5 mmol) of bis[ll-methoxycarbonylundecyl] dilellurium and 20 ml of methanol. Excess sodium borohydride is added and the mixture is stirred until it becomes colorless. 354mg (1.1 mmol) of l,5-diiodo-4-pentene are added, the mixture is stirred for 0.5 h, diluted with water, and extracted twice with diethyl ether. The combined diethyl ether extract is washed with water, dried with anhydrous sodium sulfate, and the solvent is evaporated. The residue is dissolved in 2 ml of benzene and chromatographed on a silicic acid column (1 x 20 cm) slurried in petroleum ether. The column is eluted with 200 ml of petroleum ether and then with 400 ml of benzene. Fractions of 20 ml are collected and fractions 16-19 are combined and evaporated yield 130 mg (22%) light yellow oil. 

A solution of a mixture of 1-acetoxymethyl-l-benzoylcyclopropane and its homoallylic partner (2.1 g, 0.0096 mol) and 1N NaOH (2 equiv) in MeOH (50 mL) was refluxed on a steam-bath for 1 h. The mixture was diluted with sat. brine and extracted with CHClj and EtjO. After drying (MgSOJ and evaporation of the solvents under vacuum on a rotary evaporator the crude product was dissolved in benzene and purified by chromatography over alumina (50 g), using petroleum ether, benzene, EtjO and MeOH as eluants. Fractions eluted with 25% EtjO in benzene up to pure EtjO were combined and the product was crystallized by the addition of EtjO/hexane yield 0.74 g (44%) mp 57-58°C. 

A sample of 2,6-dibromotetracyclo[3.3.1.0 .0 ]nonane-3,7-dione (1.00 g, 3.29 mmol) was mixed with neat BujSnH (1.90 g, 6.58 mmol) at rt and under Nj. The solid material dissolved as the mixture was warmed to 60 C. This temperature was maintained for 24 h, then more BUjSnH (1.90 g, 6.58 mmol) was added, and heating was continued for another 24 h. The entire reaction mixture was dissolved in benzene and the solution applied to a column of silica gel (30 g) packed in benzene. The column was eluted with benzene and then with CHCI3. The CHCI3 fraction gave 0.52 g of a colorless crystalline solid, mp 110-136"C. Recrystallization (benzene/petroleum ether) afforded 0.25 g (52%) of the product as colorless needles mp 153.5 154,5°C,... 

Eluent Dissolve the sample in 6 mL of petroleum ether and then gently force the oil through the filter and the two columns with pressure. Wash the columns with 2 x 0.5 mL of petroleum ether. The insoluble fraction of the oil is trapped on the filter and weighed. Wash the two columns with 2 x 1 mL of petroleum ether. Disconnect the two columns and elute both with 2 x 1 mL benzene/petroleum ether (1 3), collecting both fractions and combining. Evaporate for the weight of aromatic hydrocarbons. Elute the cyanopropyl column with 2 x 1 mL benzene/methanol (1 1) into a separate flask. Evaporate the eluate of the cyanopropyl column and weigh for the fraction of heterocyclic aromatic hydrocarbons. 

Separation of total lipids is achieved by development with mixtures of hexane, petroleum ether, benzene, chloroform, or ethyl ether. The addition of small amounts of acetic acid is recommended for clear separation of fatty acids. The main lipid classes are thus separated as shown in figure 3. After visualization of the individual fractions by non-destructive treatment or after spraying only a small part of the chromatoplate corresponding areas can be scraped off the plate and the separated compounds eluted with chloroform or ether (neutral lipids), and methanol-chloroform, methanol, methanol-acetic acid-water (phospholipids). The eluted material can be processed further. Some chemical determinations are possible in the presence of silica gel. 

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