Residues, concentration Subject

After drying over sodium sulfate and concentration to vacuum the remaining residue is subjected to chromatography over silica gel. Using a benzene-ethyl acetate mixture (19 1) there is eluated 900 mg of 6-chloro-1,2a-methylene-A -pregnadiene-17o-ol-3,20-dione-17-acetate, which upon recrystallization from isopropyl ether melts at 200° to 201°C. 

Extraction procedures must be adjusted when separated anthocyanins will be tested in biological studies. We have found that the types of acids used for anthocyanin extraction as well as their residual concentrations in the final extract may affect the results obtained from biological tests. The growth inhibitory effect of anthocyanins on HT29 (human colonic cancer) cells may be overestimated if the residual acid in the extract exerts a toxic effect on the cells. Acetic acid residues in anthocyanin extracts showed less toxicity to HT29 cells than hydrochloric acid when samples were prepared under the same extraction procedure and subjected to the same tests on HT29 cells. In addition, the procedure to remove acids affected the acid residual concentration as well in final anthocyanin extracts, with lyophilization being more successful than rotary evaporation. 

Plant materials are homogenized with methanol. Acetamiprid residue is extracted with dichloromethane by liquid-liquid partitioning. Dichloromethane is removed by rotary evaporation, and the residue is subjected to a clean-up procedure using Florisil PR column chromatography. The concentrated eluate is analyzed by gas chromatography (GC). 

To a solution of 3-benzyi-l-methylsulfinyl-1-methylsulfanylcyclobutane (2,70 g, 10.6 mmol) in Et20 was added 4.5 M H2S04 (2.8 mL). The mixture was stirred at rt for 2 d and then heated under reflux for 2 d. After addition of NaHC03 and MgS04, the mixture was further stirred for a while and the insoluble solid was filtered off. The filtrate was concentrated, and the residue was subjected to column chromatography (silica gel, CH2Cl2/hexane) to give the title compound as a colorless oil yield 1.13 g (66%). 

A solution of mixed A. jV-diethyl-l,l,2,3,3,3-hexafluoropropanamine (10) and 11 (2.2 g, 10 mmol) in CH,C12 (15 mL) was added dropwise to a solution of ethyl 2-hydroxy-2-(4-tolyl)acetate (14 0.78 g, 4 mmol) in CH2C12 (20 mL) at rt. After stirring for 24 h, the mixture was poured into H20 and was extracted with i-Pr20. The combined organic layers were washed with H20, dried (Na,CO,) and concentrated. The residue was subjected to column chromatography (silica gel, hexane/EtOAc 9 1). The first elution gave ethyl 2-fluoro-2-(4-tolyl)acetate (15) yield 0.47 g (60%). 

To a stirred mixture of 14 [39] (493 mg, 1.0 mmol), NaCNBH, (383 mg, 6.0 mmol) and 3-A molecular sieves in MeCN (20 mL) at room temperature was added as solution, kept at 0°C, of MejSiCl (652 mg, 6.0 mmol) in MeCN (6 mL). The reaction mixture was stirred for 5 h at room temperature, filtered through Celite, and poured into ice-cold saturated aqueous NaHCOj. The aqueous phase was repeatedly extracted with CHjClj. The combined extracts were washed with saturated aqueous NaHC03, dried (MgSOj), filtered, and concentrated. The residue was subjected to silica gel column chromatography (toluene/ethyl acetate 2 1) to yield 15 (375 mg, 76%), [< ] +19.3° (c 1.0, CHClj). Regioisomer 16 (13%) was also obtained. 

Methoxybenzaldehyde lb (136 mg, 1 mmole) and NH2OHHCl (84 mg, 1.2 mmole) were mixed thoroughly with NH4OAC (108 mg, 1.4 mmole). The resulting powder was taken in a test tube, kept in an alumina bath inside a micro-wave oven and irradiated for 1 min. The mixture was removed from the oven, cooled and shaken with CHC13 (15 mL). After filtration, the filtrate was concentrated and the residue was subjected to column chromatography over silica gel using hexane-EtOAc (7 3) as eluent to afford 4-methoxybenzonitrile 2b (119 mg, 90%). 

Drug, and Cosmetic Act, Sections 408 and 409 for setting tolerances. A tolerance is the legal maximum residue concentration of a specific pesticide chemical allowed in or on a specific food or feed item. If residues exceed the tolerance, the food or feed is considered adulterated and is subject to seizure as it travels in interstate commerce. Tolerances are set at a level that represents the maximum residue likely to occur if the pesticide is used in accordance with the registered directions for use. 

To a solution of 2-iodo-5-(4-fluorophenylmethyl)thiophene (5.30 g, 16.6 mmol), in anhydrous DMF (5.0 ml) was added (R)-N-hydroxy-N-(3-butyn-2-yl)urea (2.12 g, 16.6 mmol), triphenylphosphine (84.0 mg, 0.32 mmol), bis(acetonitrile)palladium(II) chloride (40.0 mg, 0.16 mmol), copper(I) iodide (16.0 mg, 0.08 mmol), and diethylamine (5.6 ml). The mixture was stirred under nitrogen at room temperature for 22 h and concentrated in vacuum at 32°C. The residue was subjected to chromatography on silica eluting with 2-7% MeOH in CH2CI2, crystallization from ethyl acetate-hexane and trituration in CH2CI2 to afford (R)-N- 3-[5-(4-fluorophenylmethyl)thien-2-yl]-l-methyl-2-propynylVN-hydroxyurea as a cream-colored solid 0.94 g (18%), melting point 135°-136°C, (dec). 

The residue was subjected to azeotropic operation with toluene two times, and ether was added to the residue. The precipitate derived from trioxane was removed by filtration and washed with ether, and the combined ethereal solutions were concentrated under reduced pressure. The residue was dissolved in ethyl acetate, and the solution was washed with water and aqueous saturated solution of sodium chloride, was dried, and was concentrated to give 4 g of an oily material. The oily material was dissolved in 20 ml of methanol and to the solution was added 20 ml of aqueous 1 N solution of sodium hydroxide, and the mixture was stirred for 14 hours at room temperature. After removal of methanol under reduced pressure, water was added to the mixture, and this solution was acidified to pH 3 with aqueous 2 N hydrochloric acid. The mixture was extracted five times with ethyl acetate, and the ethyl acetate extract was dried and concentrated to give 3.5 g of crude crystals. After addition of ethanol to the crude crystals, the crude crystals were filtered. The filtrate was concentrated, and to the residue was added ethanol and ethyl acetate, and precipitate was collected by filtration. The combined amount of the crude crystals was 1.6 g. After the combined crude crystals were methylated with diazomethane, the reaction product was dissolved in 20 ml of ethyl acetate. To this solution was added 1.5 g of sodium acetate and 300 mg of 10% palladium-carbon, and the mixture was stirred for 2 hours under hydrogen. Then, the reaction product was filtered, and after addition of aqueous saturated solution of sodium hydrogen carbonate to the filtrate, the mixture was extracted two times with ethyl acetate. The extract was washed with an aqueous saturated solution of sodium chloride, dried, and concentrated to give 1.3 g of crude crystals. The crude crystals were recrystallized from ethyl acetate to yield 765 mg of the title compound (melting point 134-135°C, yield 43%). 

Then the residual oil was dissolved in 5 ml of acetic acid, and to the solution were added 5 ml of tetrahydrofuran and 2 ml of water. After the mixture was stirred for 14 hours at 50°C and concentrated, the residue was subjected to azeotropic operation two times with toluene. The residue was purified by column chromatography on silica gel using ethyl acetate-cyclohexane (1 2) to give 280 mg of the pure compound (yield 70%). 

A solution of S-iodomethyl-6a,9a-difluoro-lip-hydroxy-16a-methyl-3-oxo-17a-propionyloxyandrosta-l,4-diene-17p-carbothioate (310 mg) in acetonitrile (10 ml) was stirred with silver fluoride (947 mg) for 3 days at room temperature in the dark. Ethyl acetate (100 ml) was added and the mixture was filtered through kieselguhr. The filtrate was washed successively with 2 N hydrochloric acid, water, saturated brine, then dried. The solvent was removed and the residue was subjected to column chromatography in chloroform then chloroform-acetone (19 1). The product was eluted with ethyl acetate and crystallised on concentration of the solution to give S-fluoromethyl 6a,9a-difluoro-lip-hydroxy-16a-methyl-3-oxo-17a-propionyloxyandrosta-l,4-diene-17p-carbothioate (0.075 g) melting point 272-273°C (dec.), [a]D= +30° (c 0.35). 

HMDS is used in the synthesis of linear polymethylsiloxane liquids and as a solvent in the synthesis of hexamethyldisilazane the concentrated PMS-lb, PMS-l,5b and tank residue are subjected to further rectification. 

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