Column of silica gel

Ethyl o-nitrocinnamate (1 mmol) was dissolved in triethyl phosphite (5 mmol) and heated at 170°C for 3 h. The triethyl phosphite and triethyl phosphate were removed in vacuo. The residue w as eluted through a column of silica gel using CHCI3 and the product recrystallizcd from CHCl3-hexane. The yield was 94%. 

Bibenzyl [103-29-7] M 182.3, m 52.5-53.5 . Crystd from hexane, MeOH, or 95% EtOH. It has also been sublimed under vacuum, and further purified by percolation through columns of silica gel and activated alumina. 

Perfluorocyclohexane [355-68-0] M 300.1, m 51° (sublimes), b 52". Extracted repeatedly with MeOH, then passed through a column of silica gel (previously activated by heating at 250°). 

Russell et al. Anal Ghent 50 2961 1986.] The material was free from anthracene derivatives. Another purification step involved passage of pyrene in cyclohexane through a column of silica gel. It can be sublimed in a vacuum and zone refined. [Kano et al. J Phys Ghent 89 3748 1985.]... 

Dried with CaH2, then passed through a column of silica gel to remove oleFinic impurities and fractionally distd. Freed from peroxides and moisture by refluxing with sodium, then distilling from LiAlH4. Alternatively, peroxides can be removed by treatment with aqueous ferrous sulfate and sodium bisulfate, followed by solid KOH, and fractional distn from sodium. 

Chromomycin A3 [7059-24-7] M 1183.3, m 185 dec, [a] -57 (c 1, EtOH). Dissolve reagent (lOg) in EtOAc and add to a column of Silica Gel (Merck 0.05-0.2microns, 4x70cm) in EtOAc containing % oxalic acid. Elute with EtOAc+1% oxalic acid and check fractions by TLC. Pool fraction wash with H2O thoroughly, dry and evaporate. Recryst from EtOAc. The hepta-acetate has m 214°, [a] -20° (c 1, EtOH). [Tetrahedron 23 421 7967 J Am Chem Soc 91 5896 1969.]... 

To a solution of nitroolefin 4 (200 mg) and isocyanide 16 (169 mg) in a 1 1 mixture of THF and isopropanol (5 mL) was added the guanidine base A -t-BuTMG (180 mg). The resulting solution was heated to 50°C for 3 h, poured into water, and extracted with dichloromethane. The organic layer was dried over sodium sulfate and filtered through a short column of silica gel (eluent dichloromethane). Evaporation under vacuum of the solvent gave the desired pyrrole as a pale crystalline solid (272 mg, 90%) mp... 

F rom 5-deoxy-5-iodo-1,2-0-isopropylidene-/ -l-arabinofura-nose (37). Anhydrous silver fluoride (600 mg.) was added to a solution of 300 mg. of 37 in pyridine (4.0 ml.), and the mixture was shaken at room temperature for 24 hours. Ether (4 ml.) was added, and the mixture was passed through a column of silica gel (1.5 X 12 cm.). The column was washed with ether/pyridine, 1 1 v/v. (10 ml.), and the effluent, which contained 5-deoxy-l,2-0-isopropylidene-/ -L-threo-pent-4-enofuranose (33), was concentrated to 4 ml. Acetic anhydride (0.2 ml.) was added, and the reaction mixture was kept at room temperature for 16 hours. Concentration afforded a sirup from which the last traces of solvent were removed by storage in high vacuum at 20°C. The sirup was distilled at 90°C. (bath) at 2.5 X HHmm. The distillate (110 mg., 51%), which crystallized on standing, had physical constants which were identical to material prepared as above. 

Purification of luciferin (Rudie etal., 1976). The luciferin fractions from the DEAE-cellulose chromatography of luciferase were combined and concentrated in a freeze-dryer. The concentrated solution was saturated with ammonium sulfate, and extracted with methyl acetate. The methyl acetate layer was dried with anhydrous sodium sulfate, concentrated to a small volume, then applied on a column of silica gel (2 x 18 cm). The luciferin adsorbed on the column was eluted with methyl acetate. Peak fractions of luciferin were combined, flash evaporated, and the residue was extracted with methanol. The methanol extract was concentrated (1 ml), then chromatographed on a column of SephadexLH-20 (2 x 80 cm) usingmethanol asthe solvent. The luciferin fractions eluted were combined and flash evaporated. The residue was... 

Purification of the activation products (PMs). The methylamine activation product dissolved in methanol is purified by chromatography, first on a column of silica gel using a mixed solvent of chloroform/ethanol, followed by reversed-phase HPLC on a column of divinylbenzene resin (such as Jordi Reversed-Phase and Hamilton PRP-1) using various solvent systems suitable for the target substance (for example, acetonitrile/water containing 0.15% acetic acid). 

To a solution of 0.18 g (1 mmol) of /V-benzylideneaniline in F.t,0 is added 0.194 g (1.1 mmol) of 9-(2-butenyl)-9-borabicyclo[3.3.1]nonane (crotyl-9-BBN) at — 78 °C. The reaction is quenched at O C with several drops of coned [ICl. The mixture is stirred overnight at r.t.. and a 3 N aq soln of NaOH is added at 0°C to make the solution basic. The mixture is extracted twice with ht20. dried, condensed, and filtered through a short column of silica gel (hexane/Et20 10 1) to remove the 9-BBN residue. 

A solution of 4.5 g (19.9 mmol) 4-(fm-butyldimethylsilyloxy)-2-cyclohexenone and 452 mg (1 mmol) of mercury(II) iodide is stirred at r.t. for 15 min and then cooled to — 78 °C. 5.03 g (24.8 mmol) of 1-ethoxy-1-(tm-bulyl(iimethylsilyloxy)ethene are added dropwise during 15 min. The mixture is stirred at — 78 °C for 2 h, quenched with 302 mg (3 mmol) of triethylamine and allowed to warm to r.t. The mixture is filtered through a short (3 cm) column of silica gel (deactivated with a 5% triethylamine solution in hexane/ethyl acetate, 10 1) eluting with hexane/ethyl acetate (10 1) and concentrated in vacuo. Purification of the crude material by flash chromatography (silica gel, hcxanc/cthyl acetate 30 1) gave the adduct as a colorless oil yield 7.98 g (18.7 mmol, 94%) d.r. (cisjtrans) 95.2 4.8. 

Woelm nylon column DCC-5 was used, giving a packed column of silica gel 66-67 cm. high and 32 mm. in diameter. 

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