Boronate column chromatography

Isolation by Boronate Column Chromatography of in Vivo Existing ADP-Ribose Protein Conjugates... 

Liu (12) had reported that III could be conveniently separated from IV by selective thioketalization to V followed by purification by column chromatography. Accordingly, a mixture of approximately 70% III and 30% IV (60.9 g) was treated with 1,2-ethanedithlol (50 ml) and boron trifluoride etherate (6 ml). The crude product was distilled under reduced pressure to yield 45.1 g (54.4%, 77.6% based upon III as starting material) of crude V, sufficiently pure for the next step. Column chromatography of lower boiling impure fractions furnished the dithioketal VI (10% yield), unreacted IV, and additional V. ... 

Boron trifluoride-mediated acylation of pyrrolidine-2,4-dione 68 led to the isolation of the neutral boron difluoride complex 2, which was sufficiently stable to be purified by column chromatography (Equation 18). This compound has been characterized crystallographically as noted above <1990J(P1)1959>. 

A 100-mL flask protected with a positive pressure of nitrogen is charged with 11 mmol of a 0.25 M pentane solution of iodo(diisopinocampheyl)borane [derived from ( +)-a-pinene]. The solution is cooled to — 100 C and treated dropwise with a solution of 980 mg (10 mmol) of 1,2-epoxycyclohexane in 2 mL of pentane. After stirring the solution for 0.5 h at —100 CC, the mixture is quenched by the addition of 1.8 mL (excess) of butanal. The mixture is allowed to warm gradually to r.t. and stirred for an additional 1 h. By that time "B NMR indicates clean formation of boronate [R OB(OEt)Ipc, d = 31], The mixture is diluted with 50 mL of pentane and treated with a 4 M THF solution of 12 mmol of 2.2 -diethanolamine. After the solution is stirred for 0.5 h, the precipitated boronate 2,2 -diethanolamine complex is filtered off and the filtrate is washed with water and brine and dried with anhyd Na2S04. The solution is concentrated under reduced pressure and the residue is purified by column chromatography followed by crystallization from pentane to provide the title compound in 89% yield mp 44 - 45°C [a] 3 —31.6 (c = 5, CHClj). 

A flask was charged with 4-bromo-iodobenzene (0.079 mol), 4-methoxy-2-methyl-phenyl boronic acid (0.087 mol), palladium acetate (0.004 mol), and triphenyl phosphine (0.008 mol) and then treated with 200 ml acetone and 250 ml 2M NaHCO i. The mixture was refluxed at 65°C for 18 hours and was then treated with water and diethyl ether and the organic layer isolated. This layer was washed with 40 ml saturated sodium chloride solution and water, dried over MgSC>4, filtered, and concentrated. The residue was purified by column chromatography using silica gel with CH2C12/ hexane, 1 1, and then recrystallized in / , 7 3, respectively, and 16.4 g of product isolated. 

A reactor containing an ice-cooled solution of the step 2 product (19.76 mmol) dissolved in 150 ml THF was treated dropwise with -butyl lithium (2.5M in hexanes 19.76 mmol) and after 2 hours treated with pinacol boronate (21.72 mmol). The ice bath was then removed and the mixture stirred overnight at ambient temperature. The reaction was quenched with aqueous NH4CI and the mixture extracted three times with 70 ml of ethyl acetate. Combined extracts were then washed with brine, dried over MgSC>4, and concentrated. The residue was purified by column chromatography on silica eluting with petroleum ether/ethyl acetate, 9 1, respectively, and 9.52 g of product isolated as a blue oil. 

The reaction of diols with alkylating agents can also be performed such that approximately the theoretical amount of monoalkylated product is obtained. Some substrates can even be monoalkylated [36, 41, 42] or monoarylated [43] with substantially higher yields than statistics would predict what must be due to the slowness of the second alkylation. This behavior, however, is not usually observed, and other strategies must usually be used to achieve clean monoalkylations. Use of excess diol will often furnish pure monoalkylated diol, but a suitable means of removal of excess diol will be required. In the examples sketched in Scheme 10.10 the products were purified by column chromatography, recrystallization, or distillation. As with acylations, the formation of monoalkylated diols can also be promoted by Ag20 [44] or by transient protection with boron [45] or tin [46] derivatives. 

Prostaglandins are preferably chromatographed in the form of their silyl derivatives, which are particularly suitable when profiling these substances in biological samples [506], Sometimes they are combined with methyl esters [547] and n-butyl boronates [548] with the aim of improving the separation and using a combination with MS. Albro and Fishbein [549] separated substrates into three fractions by column chromatography. 

From the known, differential complexing between boronic acids and polyhydroxy compounds, it follows that carbohydrate mixtures may be separated by column-chromatographic methods that exploit the differences. Nucleoside and nucleotide boronates have been separated on columns of anion-exchange resins,90 and sugars and alditols have been shown to be differentially retained on such resins in the sulfonated phenylboronic acid form,64 but perhaps the best uses of column chromatography in this connection have incorporated the resolving powers of insoluble polymers to which boronic acid groups have been covalently bonded. Such insoluble forms of boronates have been synthesized either by substitution of polysaccharide derivatives, or by polymerization of suitable arylboronic acids. 

Affinity chromatography Has a wide number of uses and can be applied to the isolation and purification of virtually all biomolecules. Specific applications include nucleic acid purification, protein purification from cell and tissues extracts, and antibody purification from blood serum. There are a number of matrices used for the construct, and some examples of these and their uses are as follows heparin columns to separate cholesterol lipoproteins, lectin columns to separate carbohydrate groups, and phenyl boronate columns to separate glycated haemoglobins. 

Dihydroxyphenylalanine-containing proteins. Boronate affinity chromatography is used in the selective binding of proteins containing 3,4-dihydroxyphenylalanine to a m-phenylboronate agarose column and eluted with IM NH4OAC at pH 10. [Hankus et al. Anal Biochem 150 187 7956.]... 

Streptozotocin-induced diabetic rats also had high levels of glycated Cu,Zn-SOD in the erythrocytes (K9) and lens, as judged by affinity chromatography on a boronate column (see Fig. 10). As described above, much of the glycated... 

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