Closing barbituric acid

Interestingly enough, a closely related protocol was successfully proposed for the synthesis of spirooxindoles-containing tetrahydrochromene skeletons when aromatic aldehydes were switched for isatin derivatives. This high-yielded reaction was performed with dimedone, 4-hydroxycoumarin, or barbituric acids in water using triethylbenzylammonium chloride (TEBA) as catalyst (Scheme 36) [125]. A Knoevenagel condensation occurred first between isatin and malonitrile derivative, followed by Michael addition of 1,3-dicarbonyl substrates and cyclization to the cyano moiety. 

IM sodium hydroxide. To die outer compartments add 0.5 ml of die serum or blood sample, and 0.5 ml of normal serum or whole blood (blank) respectively immediately close the cells and carry out the following procedure on each cell. Gently agitate the cells, ensuring that the contents of the two compartments do not mix, and allow to stand for at least 2 hours. Transfer 0.1 ml of the solution from the inner compartment to a tube containing 1 ml of the Phosphate Solution, add 0.5 ml of a 0.25% solution of Chloramine-T, mix, allow to stand for 3 minutes, add 1.5 ml of the Barbituric Acid and Pyridine Reagent, mix, and allow to stand for... 

The results of correlation analysis for barbituric acid derivatives should be interpreted carefully, bearing in mind that the majority of results deal only with compounds (sometimes a few) used in therapy, which restrict the full representation of the class. Although highly significant correlations are observed for closely related compounds, the generalization of such correlations often lowers their significance. Some problems can also be encountered with appropriate determination and/or selection of experimental data and parameters used in correlation analysis, but one can assume that this method will be further developed and will expand the range of its applicability, as indicated in more recent papers.572,573... 

Nevertheless, the dihydropyrimidinase seems to be closely related to the barbitur-ase (E.C. 3.5.2.1), which is able to hydrolyze barbituric acid 391 (Fig. 12.4-8). 

The X-ray structure for the disodium salt of pyrimido[5,4-J]pyrimidine-2,4,6,8-tetrol has been determined. The molecule is planar, but the bond distances reported indicate that it is only partially aromatic. In particular, the bond distance C4-C4a is significantly greater than the normal bond distance of aromatic compounds and is approximately equal to that of a C(sp2) C.(sp2) single bond. The C—C and 0-0 bond distances for this compound bear a close resemblance to similar bond distances obtained for barbituric acid derivatives.176 The X-ray structures of pyrimido[5,4-rf]pyrimidine nucleosides1 73177 and dipyridamole178 have also been reported. 

Anti-inflammatory agents—Al number of l,3-diphenyl-5-substituted barbituric acid derivatives (XXXIX) have been prepared for evaluation as antiinflammatory agents [188-190] since their structures are closely analogous... 

Transfer 10 ml of the absorption solution from the 23 ml measuring flask to another 23 ml measuring flask and add in turn exactly 2 ml buffer solution, 4 ml 1 m hydrochloric acid and 1 ml chloramine T solution, shaking the flask constantly. Close the flask and leave to stand for at least 1 min, but not more than 3 min.. Now add 3 ml barbituric acid-pyridine reagent, top up to the 23 ml mark with distilled water and shake well. After 20 min. 

Surface-complexed iron [Fe ] observed after intrapleural injection of 30 mg of either amosite, crocidolite, and chrysotile both genuine and saturated with Fe in Sprague-Dawley rats corresponded to oxidant generation, measured as barbituric acid reactive products of deoxyribose, and more covalently closed, circular DNA strand scission induced by these asbestos fibres (Ghio et al. 1994). 

The barbiturates, which include several important drugs used as sedatives (tranquilizers) and hypnotics (sleep-producers), are closely related to the pyrimidines. The structural formulas of barbituric acid and two of its derivatives are given below in these formulas the distribution of the hydrogen atoms between oxygen and nitrogen is uncertain, and... 

Closely related to the Pinner protocol are (a) the base-catalyzed condensations of ureas with malonates to afford derivatives of barbituric acid (e.g., 18, cf p. 473), (b) the condensations of ureas with cyanoacetates promoted by Ac2 O (-> cyanoacetyl ureides 19) followed by base-induced cyclization to give 4-aminouracil derivatives (19 — 20) [258] ... 

There are examples of weak acids reabsorbed by simple nonionic diffusion which urinary excretion is not influenced by changes in urine pH. It is the case if the pKa is above or close to the upper limit of urine pH, as it is the case for barbital (pKa = 7.8), and a few other barbiturates. Also, if the pKa value is very low, such as it is the case for 2-nitroprobenecid (pKa=1.3), the acid remains mainly unionized in the physiological range of urine pH [15], and its excretion remains independent of fubular urine pH. 

Mercuric sulfate. Forms white precipitate with barbiturates, glutethimide, and phenytoin. Suspend 5g of mercuric oxide in lOOmL of water. Add, while mixing, 20 mL of concentrated sulfuric acid. Cool and dilute to 250 mL with water. This reagent is stable indefinitely at room temperatures in a closed container. 

Synthetic approaches to optically pure enantiomers of barbiturates followed general methods of preparation of these compounds, but pure enantiomers of known configuration have been used as the substrates. Thus, R(—) and S(+) enantiomers of 51 and closely related compounds (54) were prepared from the enantiomers of 3-methylhexanoic acid (53) by the reaction sequence shown in Scheme 6.73,200... 

Hydrolysis was the accompanying reaction to the reduction of 5,5-diallylbarbituric acid with NaBH4309,364 and to the N-methylation of different barbiturates.363-367 The effects of different protecting agents and solubilizers on the stability of medicinal barbiturates also deserve close attention because of their pharmaceutical importance.335,368-375 The stability of barbiturates in frozen systems has also been investigated.327 376 377... 

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