Urea derivatives, analysis

In the recent method of Zienmiak, et al3 3, a liquid chranatographic procedure has been developed which separates and permits quantitative analysis of cimetidine (I), cimetidine sulfoxide (II), its hydroxymethyl (111) and guanol urea derivatives (IV). Metiamide, SK F 92058, is used as the internal standard. Their procedure involves the precipitation of protein with acetonitrile, addition of anhydrous K2HPOit, extraction of the separated aqueous phase with methylene chloride and KH2POi, to saturate and salt out the solution. The methylene chloride is evaporated to dryness, the sample is reconstituted with mobile phase (CHaCbhCE OIbl OtNihOH,... 

Debnath, A.K. (1998). Comparative Molecular Field Analysis (CoMFA) of a Series of Symmetrical Bis-Benzamide Cyclic Urea Derivatives as HIV-1 Protease Inhibitors. J.Chem.Inf.Com-put.ScL, 38,761-767. 

Dehnath, A.K (1998) Comparative molecular field analysis (CoMFA) of a series of symmetrical his-henzamide cyclic urea derivatives as HIV-1 protease inhibitors./. Chem. Inf. Comput. Sci., 38, 761-767. 

Hemmateenejad, B., Miri, R., Tabarzad, M., Jafarpour, M. and Zand, F. (2004) Molecular modeling and QSAR analysis of the anticonvulsant activity of some N-phenyl-N°-(4-pyridinyl)-urea derivatives./. Mol. Struct. (Theochem), 684, 43-49. 

Thus, for instance, the formation of trimethylsilyl esters, alcohols and phenols or other hydroxyl-containing compounds not only improves chromatographic separations, but also is a method for the analysis of hydroxyl groups. The reagents used in this instance are, however, not very selective as they react with several classes of compounds. For instance, N,0-bis(trimethyl)acetamide also reacts with organic acids, amines, aromatic amides, urea derivatives and some enols [19, 20]. Therefore, this technique should desirably be used in combination with other methods or for converting involatile... 

Analysis of Urea Derivative Herbicides in Water and Soil... 

A recent paper by EPA reviewed the results of analysis of about 300 pesticides for nitrosamines. A large number of amide, carbamate, organophosphate, triazine, urea derivatives and miscellaneous nitrogen-containing pesticides did not contain... 

Kappelmeier [35] has suggested the use of aniline, benzylamine, and phenyl-ethyl-amine as reagents for the identification and analysis of urea in UF resins. He has provided evidence that the methylene-ether groups form a bridge between urea residues in UF resins. The use of benzylamine in particular (which yields dibenzylurea from urea derivatives), has been developed as a method of analysis. In determining the ratio of urea to formaldehyde in UF resins, the benzylamine method has been coupled with a process of formaldehyde estimation which involves depolymerization with phosphoric acid, followed by distillation into alkaline potassium cyanide solution [36]. 

Another application of this concept, in this case to an intermolecular process, the Povarov reaction, was reported by Jacobsen s group in 2010 [150]. The reaction was efficiently catalyzed by o-nitrobenzenesulfonic acid in the presence of a chiral urea derivative. The authors performed a detailed experimental and computational analysis of this catalyst system, which supported the mechanism shown in... 

Scheme 3) (13). All these leads were identified using structural information gathered from extensive work on peptide leads and a computational pharmacophore analysis design approach. Much attention and focus has been placed on cyclic ureas and dihydropyranones. The research efforts on cyclic urea derivatives resulted in some of these inhibitors being selected for clinical evaluation (12-15, Schemed) [13]. The research on dihydropyranones resulted in the recent approval of Tipranavir (7) for HIV treatment, which is given in combination with Ritonavir (3) [46,47].

Di Corcia, A., Analysis of urea derivative herbicides in water and soil, in Chromatographic Analysis of the Environment, Nollet, L.M.L. (Ed.), CRC Press, Boca Raton, FL, 2006. 

C. J. Umberger and G. Adams, Identification of Malonyl Urea Derivatives. Infrared Absorption in Toxicological Analysis, Anal. Chem. 24,1309,1952. 

---