1,3-Dibenzylthiourea and 1,3-Dicyclohexylthiourea

Synthesis, crystal structure and thermal properties of bis-(1,3-di-cyclo-hexyl-thio-urea-κS)bis(iso-thiocyanato-κN)cobalt(II)

Crystals of the title compound, [Co(NCS)2(C13H24N2S)2], were obtained by the reaction of Co(NCS)2 with 1,3-di-cyclo-hexyl-thio-urea in ethanol. Its crystal structure consists of discrete complexes that are located on twofold rotation axes, in which the CoII cations are tetra-hedrally coordinated by two terminal N-bonded thio-cyanate anions and two 1,3-di-cyclo-hexyl-thio-urea ligands. These complexes are linked via inter-molecular N-H⋯S and C-H⋯S hydrogen bonding into chains, which elongate in the b-axis direction. These chains are closely packed in a pseudo-hexa-gonal manner. The CN stretching vibration of the thio-cyanate anions located at 2038 cm-1 is in agreement with only terminal bonded anionic ligands linked to metal cations in a tetra-hedral coordination. TG-DTA measurements prove the decomposition of the compound at about 227°C. DSC measurements reveal a small endothermic signal before decomposition at about 174°C, which might correspond to melting.

Computational Study of the Interaction between TIBO Inhibitors and Y181 (C181), K101, and Y188 Amino Acids

The non-nucleoside inhibitors of HIV-1 reverse transcriptase (NNRTIs) are an important class of drugs employed in anti-HIV chemotherapy. TIBO compounds, which belong to the NNRTIs class, are potent inhibitors of the HIV-1 reverse transcriptase enzyme (HIV-1 RT). However, mutations in the amino acids present in the active site of these inhibitors limit their clinical use. In this work, the intermolecular interactions taking place between compounds of the TIBO family and Y181 (C181), K101, and Y188 amino acids are investigated. For this purpose the coordinates of three RT crystalline structures complexed with TIBO were taken from PDB database, and were analyzed by means of the B3LYP/6-31+G(d,p) model. The natural bond orbital (NBO) and atoms in molecules (AIM) methods indicate that not only does the Y181C mutation lead to loss of favorable interactions between the TIBO side chains and tyrosine, but it also affects the interaction between the inhibitor and K101 and Y188. Results also revealed that the interaction between TIBO and K101 is stabilized by N-H...O and N-H...S hydrogen bonds. This is the first time that the presence of the latter hydrogen bond (N-H...S) is reported to play an important role in the stabilization of the interaction between TIBO and K101. In addition the NBO and natural population analyses (NPA) indicate that the 8 Cl-TIBO inhibitor presents a more effective interaction with the Y181, K101, and Y188 than that of 9 Cl-TIBO.

The conformational equilibrium of N,N'-bis[(S)-1-phenylethyl]-thiourea and its solvent dependence, studied by NMR and CD spectra and by X-ray crystallography

Favoured conformations of N,N'-bis[(S)-1-phenylethyl]thiourea (1) have been predicted by empirical force-field calculations, and the corresponding rotational strengths for the important transitions in the near UV region have been calculated. Experimental studies by 1H NMR, IR, UV, and CD spectroscopy have permitted the assignment of a conformation denoted E,Za to the conformer, which dominates in nonpolar solvents, while hydroxylic solvents were found to favour conformations of Z,Za type. The E,Za conformer is also predicted by force-field calculations to be the most stable one.Key words: circular dichroism, conformation, crystal structure, dynamic NMR spectroscopy, N,N'-bis[(S)-1-phenylethyl]thiourea.