Metho p-toluene sulfonate

The N-3 position of uracil also can be modified with carbodiimide reagents. In particular, the water-soluble carbodiimide CMC [l-cyclohexyl-3-(2-morpholinoethyl) carbodiimide, as the metho p-toluene sulfonate salt] can react with the N-3 nitrogen at pH 8 to give an unstable, charged adduct. The derivative is reversible at pH 10.5, regenerating the original nucleic acid base (Figure 1.47). Cytosine is unreactive in this process. 

A good source of uncommon bases is tRNA. It provides substrates for studying the effect of base on the rate of hydrolysis. Baev et al. (62) showed that V2-dimethylguanylyl-(3 -5 )-cytidine-3 phosphate (G2m-pCp) was hydrolyzed much slower than the usual GpCp. Venkstern (63) reported that Tp was hydrolyzed very slowly. Naylor et al. (64) found that Cp was hydrolyzed with half the rate of CpU. The same group of workers introduced (64, 65) a chemical block on uridine and pseudo-uridine residues by reacting RNA with l-cyclohexyl-3-(2-morpho-liny]-(4)-ethyl)-carbodiimide metho-p-toluene sulfonate. The modification of the uridine residues completely blocked the action of venom exonuclease and also blocked the action of pancreatic RNase. 

To avoid any possible a — 7 conversion promoted by the anhydrous conditions during esterification Franzblau (1962) and Franzblau el al. (1963) developed a method by which the hydroxamic acids could be formed directly from the unmodified proteins in an aqueous system. This was achieved using a water-soluble carbodiimide, 1-cyclohexyl-3[2-morpholinyl-(4)-ethyl]-carbodiimide metho-p-toluene sulfonate (Fig. 5). The reaction conditions (pH 4, 25°C, in aqueous medium) eliminated any possibility of a —> 8 conversion. These conditions also precduded the possibility of hydroxyaminolysis of the natural ester linkages of collagen which will be discussed in Section V. This method, in common with all the others used to study 7-glutamyl links, was not quantitative. After subsecpient dini-... 

Wash with PBS and react either with 4% (v/v) l-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide metho-p-toluene sulfonate (CMC) 10 min or with 8% (v/v) OA in distilled water (2 h in the latter case treatment with acetic anhydride in step 2 is omitted). 

Howton and Golding (115) reduced methyl 2-phenacylpyridinium bromide in methanol with platinum oxide and obtained an 88% yield of l-methyl-2-phenacylpiperidine hydrobromide. In another reduction they allowed uptake to proceed further and claimed that 20% of 1-methyl-2-(hexahydrophenacyl)piperidine was formed. In the hydrogenation of the methobromide and metho-p-toluene sulfonate of 2-phenacylpyridine l-methyl-2-phenacylpiperidine was obtained (116). When the methiodide compound was reduced about 8% of l-methyl-2-(2-hydroxy-2-phenethyl)piperidine was also obtained. 

Cyclohexyl - 3 - ( 2 - morpholinoethyl) Carbodiimide metho - p - toluene sulfonate... 

Figure 4. Variation of coupling efficiency with the concentration of coupling agent l-cyclohexyl-3-[2-morpholinyl-(4)-ethyl] carbodiimide metho-p-toluene sulfonate. Conditions time, 60 min collagen, 2.5 mg/ml co(AAc/AAm)lV, 20 mg/ml.

The coupling together of acrylic-based copolymers and acid-soluble collagen via l-cyclohexyl-3-[2-morpholinyl-(4)-ethyl] carbo-diimide metho-p-toluene sulfonate has proven successful. From the results presented here it is evident that, for the heterogeneous reaction carried out in air, the following conclusions may be drawn ... 

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