Tautomeric preferences among glycocyamidines
01 Oct 1971-Journal of the American Chemical Society (American Chemical Society)-Vol. 93, Iss: 21, pp 5552-5560
About: This article is published in Journal of the American Chemical Society.The article was published on 1971-10-01. It has received 62 citations till now.
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TL;DR: An artificial receptor has been designed to bind creatinine with a color change (chromogenic response) caused by proton transfer from one end of the receptor to the other, showing "induced fit" binding resulting from electronic complementarity between host and guest.
Abstract: An artificial receptor has been designed to bind creatinine with a color change (chromogenic response) caused by proton transfer from one end of the receptor to the other. The receptor was synthesized and found to extract creatinine from water into chlorocarbon solvents. The color change in the organic layer is specific for creatinine relative to other organic solutes, and it is selective for creatinine relative to sodium, potassium, and ammonium ions. The chromogenic mechanism is revealed by x-ray crystal structures of creatinine, the free receptor, and the complex, showing "induced fit" binding resulting from electronic complementarity between host and guest.
94 citations
81 citations
TL;DR: In this paper, the degradation and carbon mineralization efficiencies of the target contaminants were investigated at different initial concentrations at different pH values (pHo 3.0, 6.2 and 11.0).
71 citations
TL;DR: Condensations of indol-3-carboxaldehyde or of its 6-bromo derivative 14 with hydantoin or 3-methylhydantoin, or 1,3dimethylHydantoin give the prevalent natural aplysinopsins with high stereospecificity.
Abstract: From the scleractinian coral Tubastraea sp. (Dendrophylliidae) collected at Palawan, Philippines, 3′-deimino-3′-oxoaplysinopsin (4) and 6-bromo-3′-deimino-3′-oxoaplysinopsin (6) are now isolated as 5:2 mixtures of (E/Z) stereoisomers. The 3′-deimino-2′,4′-bis(demethyl)-3′-oxoaplysinopsin (7) and 6-bromo-3′-demino-2′,4-bis(demethyl)-3′-oxoaplysinopsin (5) are isolated as 2:3 and 1:1 (E/Z) mixtures, respectively, from another dendrophylliid, Leptopsammia pruvoti, collected near Marseille, Mediterranean coast of France. Larger amounts of these and related compounds, needed for a full structural determination, are obtained by synthesis. Thus, condensations of indol-3-carboxaldehyde (9) or of its 6-bromo derivative 14 with hydantoin (15), 3-methylhydantoin (11), or 1,3dimethylhydantoin (10) give the prevalent natural aplysinopsins with high stereospecificity. The minor stereoisomers (Z)-4, (Z)-6, (E)-7, and (E)-5 are obtained by (E/Z) photoisomerization under UV light of the condensation mixtures. The configuration is assigned from larger HC(8)/C(5′) 1H, 13C couplings in the (E) than in the (Z) isomer, and, in the case of 4 and 6, from NOE enhancement at MeN(2′) on irradiation at HC(8). The stereospecificity of the condensations is attributed to steric inhibition to planarity in the rate-limiting transition states, due to N(2′)/HC(2) repulsion with (Z)-4 and (Z)-6, or to C(5′)O/HC(2) repulsion with (E)–7 or (E)-5. As the aplysinopsins undergo (E/Z ) phostoisomerization also under the daylight conditions of the laboratory, their isomeric composition in nature can not be presently assessed.
68 citations