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Thiourea Moieties (thiourea + moiety)
Selected AbstractsSynthesis and properties of novel macrocyclic compounds bearing thiourea moieties by use of chemical feature of hypervalent sulfurJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2002Noboru Matsumura Macrocyclic compounds 5a-i bearing two tetraazathiapentalene frameworks were synthesized by the reaction of 10-S-3 tetraazathiapentalene derivatives 3a-f with compounds having various diisothiocyanate functions 4a-e. The reduction of the macrocyclic compounds with NaBH4 afforded the ring-opened macrocyclic compounds 11a-b and 11e-h by elimination of the hypervalent sulfur. The structures of these compounds were established by their spectral data and also by the X-ray crystallographic analysis of lla. The other ring-opened macrocyclic compounds 14a and 14e-h that bear four thiourea groups were synthesized by alkaline hydrolysis of 5a and 5e-h in that elimination of the C=SIV moiety in the tetraazathiapentalene rings occurred. [source] Organocatalytic Asymmetric Cyanosilylation of NitroalkenesCHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2010Pablo Bernal New catalyst, new reaction: The unprecedented cyanosilylation of nitroalkenes can be efficiently catalyzed by a bifunctional quinine derivative with tetraalkylammonium cyanide and thiourea moieties. The activation of the nitroalkene by hydrogen bonding to the thiourea, together with the presence of an "active" cyanide, provides a new mode of activation that leads to products in high yields and good selectivities (see scheme). [source] Metal-Controlled Anion-Binding Tendencies of the Thiourea Unit of ThiosemicarbazonesCHEMISTRY - A EUROPEAN JOURNAL, Issue 31 2008Valeria Amendola Dr. Abstract The terdentate ligand 3 (LH, 2-formylpyridine 4-thiosemicarbazone) forms with FeII and NiII 2:1 complexes of octahedral geometry of formula [MII(LH)2]2+. X-ray diffraction studies have shown that in both complexes the thiourea moieties of the coordinated thiosemicarbazones are exposed to the outside and are prone to establish hydrogen-bonding bifurcate interactions with oxoanions. However, spectrophotometric studies in CHCl3 solution have shown that only the poorly basic NO3, ion is able to form authentic hydrogen-bond complexes with thiourea subunits, whereas all the other investigated anions (CH3COO,, NO2,, F,) induce deprotonation of the N-H fragment. The extreme enhancement of the thiourea acidity is based on the coordinative interaction of the sulphur atom with the metal, which stabilises the thiolate form, and it is much higher than that exerted by any other covalently linked electron-withdrawing substituent, for example, NO2. [source] Towards Selective Recognition of Sialic Acid Through Simultaneous Binding to Its cis -Diol and Carboxylate FunctionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2010Martín Regueiro-Figueroa Abstract A series of receptors containing phenylboronic acid and urea or thiourea units have been designed for simultaneous recognition of the cis -diol and carboxylate functions of sialic acids, which are known to be overexpressed on the surfaces of tumor cells. The interaction of the receptors with 5-acetylneuraminic acid (Neu5Ac) and 2-,- O -methyl Neu5Ac (MeNeu5Ac) in DMSO solution has been investigated bymeans of spectrophotometric titrations and 1H, 13C, and 11B NMR spectroscopy. Additionally, we have also investigated the binding of these receptors with competing monosaccharides such as D -(+)-glucose, D -fructose, methyl ,- D -galactoside, and methyl ,- D -mannoside. Our results show that 2-{[3-(4-nitrophenyl)thioureido]methyl}phenylboronic acid (3a) recognizes both Neu5Ac and MeNeu5Ac with good selectivity with regard to the remaining monosaccharides investigated. DFT calculations performed at the B3LYP/6-31G(d) level show that this selectivity is due to a cooperative two-site binding of Neu5Ac through 1) ester formation by interaction at the phenylboronic acid function of the receptor and 2) hydrogen-bond interaction between the thiourea moiety and the carboxylate group of Neu5Ac. Compound 3a can therefore be considered a promising synthon for the design of contrast agents for magnetic resonance imaging of tumors. In contrast, the analogue of 3a containing a urea moiety , compound 3b , displays strong binding to all monosaccharides investigated, due to two-site binding through interaction on the phenylboronic acid function of the receptor and a hydrogen-bond interaction between the urea moiety and the sugar hydroxy groups. [source] | ||||||||||