Guanidines ureas

Elution curves for biguanide in the presence of related compounds (e.g. cyanamide, cyanoguanidine, guanidine, urea, thiourea) have been established (690). Various ion-exchange resins are suitable (108,686,689). 

Many of the most versatile and widely used syntheses of pyrimidines are straightforward examples of [3+3] condensations of amidines, guanidines, ureas and thioureas with 1,3-dielectrophiles, and clearly a considerable measure of control over the degree and nature of the substitution pattern in the final product is possible by appropriate choice of the two three-component units. Representative examples are given in equations (112)—(115), and the use of sulfamide in place of amidines, etc., allows the method to be extended to the synthesis of polyheteroatom systems e.g. equation 116). 

This /3-barrel structure makes the enzyme very stable against denaturating stressed by SDS, guanidine, urea, heat and organic solvents. 

The indole linker 1.11 (68), easily prepared from aminomethyl PS resin and N-carboxyalkylated indole-3-carboxaldehyde, was used to support amines and to transform them on SP, obtaining, by release with TFA-DCM 1/1 in 30 min, a variety of compounds, including amides, sulfonamides, guanidines, ureas, and carbamates. 

The intrinsic pK values in the guanidine-urea mixture were found to be close to the normally expected values. The pK values for the native pro-... 

Spectrophotometric titration of the phenolic groups led to the conclusion that all of the fifty-eight phenolic groups present on each paramyosin molecule were titrated in the guanidine-urea mixture, but that only forty-nine were titrated in the native state in 0.3 M KCl. (All of these had an essentially normal pKi t of 9.6.) This conclusion however was based entirely on the fact that the total change in absorbance at 295 m/i, between neutral pH and pH 14, is about 15 % less in the native protein than in the denatured state. If the change in absorbance per group titrated were to differ in the two solvents, then the conclusion reached would have to be revised. 

The most common NCN synthons used are amidines, guanidines, ureas and thioureas. The two-carbon units arc usually suitably functionalized carbonyl compounds. 

Acyl(or cyano)pyrimidines substituted at the 4-position with chlorine, methoxy or methylsulf-anyl have also been used as intermediates in the preparation of pyrimido[4,5-rf]pyrimidines by reaction with guanidine, urea, or amidines.110114 139,140 Thus, 5-phenylpyrimido[4,5-<7]-pyrimidine-2,4,7-triamine (35) is obtained by reaction of 2-amino-4-methoxy-6-phenylpyrimi-dine-5-carbonitrile (34) with guanidine.114... 

Compounds 40 react with guanidine, urea, thiourea, methylisothiourea, guanylthiourea by Lewis-acid catalysis (00S1738) and with thiosemicarbazide, semicarbazide (99IZV361) in the presence of triethylamine to form the corresponding 5,6-oligomethylenepyrimidines and 3-hydroxy-2(thio)-carbamoyl-3-polyfluor-o a 1 k y 1 - 3.3 a. 4.5.6.7 - h e x a h y d r o - 2 / /- i n d a z o 1 e s 41, respectively (Scheme 38). The structure of 41 (thio) is confirmed by X-ray analysis. 

The main route for the formation of NOCs is by nitrosation reactions that take place between a nitrosating agent like nitrite (NOi") in an acidic environment, nitrous acid (HNO2), nitrogen oxides (NO2 or NO,c)5 nitrosyl chloride (NOCl), and, on the other hand, a nitrosable agent like some amines, amides, guanidines, urea, and urethane compounds. 

Nitroprnsside(sodium)-ferrieyanide (FGNP reagent) for aliphatic nitrogen compounds, e. g., cyanamide, guanidine, urea and thiourea and their derivatives for creatine and creatinine. 

Nitropmsside(sodiiim)-hydrogeii peroxide for guanidine, urea, thiourea and their derivatives, for creatme and creatinine. 

Odagi, M. Furukori, K. Watanabe, T. Nagasawa, K. Asymmetric a-Hydroxylation of Tetralone-Derived P-Ketoesters by Using a Guanidine-Urea Bifunctional Organocatalyst in the Presence of Cumene Hydroperoxide. Chem. Eur. J. 2013,19,16740-16745. 

Studies which have involved Lewis acid-base adducts of organoboranes include the following the adducts of phenyl boron dichloride with tetrasulphur tetranitride, dibromomethylborane and bromodimethylborane with pyridine, 4-methylpyridine, trimethylamine and trimethylphosphine, monoalkylboranes with A AWW -tetramethylethylenediamine, diethylboron esters of alkane-nitronic acids with pyridine, and triarylboranes with guanidine,urea, methylurea, and thiourea. ... 

Fox s group has extended its work on the synthesis of pseudocytidine ( -cyti-dine) (Vol. 9, p. 148) to include other 5-D-ribofuranosylpyrimidines. Thus the 3-methoxyacrylate derivative (436) reacted with guanidine, urea, or thiourea to give derivatives of i -cytidine, -uridine, and 2-thio- -uridine and their a-anomers. The D-ribofuranosyl-ethyne and -ethene derivatives (437) and... 

Under similar reaction conditions to those described with catalyst 88, the guanidine-urea bifunctional catalyst 89 (5mol%) was used for the epoxidation of ( )-enones 9, affording the corresponding epoxides 83 in excellent results... 

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