- Effect of spacer geometry on oxoanion binding by bis- and tetrakis-thiourea hosts
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Hosts with thiourea groups bind anions by formation of multiple hydrogen bonds. This contribution discusses how spacers linking two or four thiourea groups affect the host affinity and selectivity. While most of the bis-thioureas bind H2PO4- preferentially, the extent of selectivity over chloride, acetate, and H2AsO4- is determined by the size of the binding cavity. A tetrakis-thiourea is shown to exhibit a unique H2AsO4- selectivity, and the discrimination of chloride is enhanced by specific solvation in dimethyl sulfoxide.
- Leung, Annie N.,Degenhardt, Dave A.,Bühlmann, Philippe
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p. 2530 - 2536
(2008/09/18)
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- Synthesis of N-benzyl- and N-phenyl-2-amino-4,5-dihydrothiazoles and thioureas and evaluation as modulators of the isoforms of nitric oxide synthase
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Inhibition of the isoforms of nitric oxide synthase (NOS) has important applications in therapy of several diseases, including cancer. Using 1400W [N-(3-aminomethylbenzyl)acetamidine], thiocitrulline and N δ-(4,5-dihydrothiazol-2-yl)ornithine as lead compounds, series of N-benzyl- and N-phenyl-2-amino-4,5-dihydrothiazoles and thioureas were designed as inhibitors of NOS. Ring-substituted benzyl and phenyl isothiocyanates were synthesised by condensation of the corresponding amines with thiophosgene and addition of ammonia gave the corresponding thioureas in high yields. The substituted 2-amino-4,5-dihydrothiazoles were approached by two routes. Treatment of simple benzylamines with 2-methylthio-4,5-dihydrothiazole at 180 °C afforded the corresponding 2-benzylamino-4,5-dihydrothiazoles. For less nucleophilic amines and those carrying more thermally labile substituents, the 4,5-dihydrothiazoles were approached by acid-catalysed cyclisation of N-(2-hydroxyethyl)thioureas. This cyclisation was shown to proceed by an SN2-like process. Modest inhibitory activity was shown by most of the thioureas and 4,5-dihydrothiazoles, with N-(3-aminomethylphenyl)thiourea (IC50=13 μM vs rat neuronal NOS and IC50=23 μM vs rat inducible NOS) and 2-(3-aminomethylphenylamino)-4,5-dihydrothiazole (IC50=13 μM vs rat neuronal NOS and IC50=19 μM vs human inducible NOS) being the most potent. Several thioureas and 4,5-dihydrothiazoles were found to stimulate the activity of human inducible NOS in a time-dependent manner.
- Goodyer, Claire L. M.,Chinje, Edwin C.,Jaffar, Mohammed,Stratford, Ian J.,Threadgill, Michael D.
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p. 4189 - 4206
(2007/10/03)
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- Solid and Solution Phase Organic Syntheses of Oligomeric Thioureas
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In order to study supramolecular architectures built from unnatural oligomeric and polymeric structures, one must first have an efficient synthetic strategy to produce them. Oligomers built from thiourea groups should form complex secondary and tertiary structures due to the hydrogenbonding capabilities of the thioureas. Herein, both solution and solid phase synthetic procedures that yield oligomeric thioureas are described. They rely on the coupling of an isothiocyanate with an amine to produce the thiourea linkage. The monomers are derived from simple diamines. Higher yields are achieved using the solid phase method due to the ability to easily monitor the extent of reaction, to use a large excess of reagent, and to perform purification after cleavage from the solid support. A variety of oligomers are given as examples. The procedure is quite general, should be easily extended to complex monomers, and will allow the investigation of intramolecular and intermolecular interactions.
- Smith, Joseph,Liras, Jennifer L.,Schneider, Stephen E.,Anslyn, Eric V.
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p. 8811 - 8818
(2007/10/03)
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