Chiral molecules in nature are involved in many biological events; their selectivity and specificity make them of great interest for understanding the behavior of bioactive molecules, by providing information about the chiral discrimination. Inspired by these conformational properties, we present the design and synthesis of novel chiral platinum(II) complexes featuring phosphine and chloroquine ligands with the general formula [PtCl(P)2(CQ)]PF6 (where (P)2 = triphenylphosphine (PPh3) (5), 1,3-bis(diphenylphosphine)propane (dppp) (6), 1,4-bis(diphenylphosphine)butane (dppb) (7), 1,1'-bis(diphenylphosphine)ferrocene (dppf) (8), and CQ = chloroquine] and their precursors of the type [PtCl2(P)2] are described. The complexes were characterized by elemental analysis, absorption spectroscopy in the infrared and ultraviolet-visible (UV-vis) regions, multinuclear ((1)H, (13)C, (31)P, (15)N, and (195)Pt) NMR spectroscopy, cyclic voltammetry, and mass spectrometry (in the case of chloroquine complexes). The interactions of the new platinum-chloroquine complexes with both albumin (BSA), using fluorescence spectroscopy, and DNA, by four widely reported methods were also evaluated. These experiments showed that these Pt-CQ complexes interact strongly with DNA and have high affinities for BSA, in contrast to CQ and CQDP (chloroquine diphosphate), which interact weakly with these biomolecules. Additional assays were performed in order to investigate the cytotoxicity of the platinum complexes against two healthy cell lines (mouse fibroblasts (L929) and the Chinese hamster lung (V79-4)) and four tumor cell lines (human breast (MDA-MB-231 and MCF-7), human lung (A549), and human prostate (DU-145)). The results suggest that the Pt-CQ complexes are generally more cytotoxic than the free CQ, showing that they are promising as anticancer drugs.

A simple and efficient metal-free methodology for the regioselective synthesis of 1,4-disubstituted-1,2,3-triazoles has been developed by applying a novel inverse electron-demand-1,3-dipolar cycloaddition approach. The practical one-pot metal-free strategy can be accomplished with various alkylidene malononitriles and aromatic azides in the presence of base.

High-throughput experimentation and multivariate modeling allow identification of noncovalent interactions (NCIs) in monoaryloxy-pyrrolide Mo imido alkylidene metathesis catalysts prepared in situ as a key driver for high activity in a representative metathesis reaction (homodimerization of 1-nonene). Statistical univariate and multivariate modeling categorizes catalytic data from 35 phenolic ligands into two groups, depending on the substitution in the ortho position of the phenol ligand. The catalytic activity descriptor TON1h correlates predominantly with attractive NCIs when phenols bear ortho aryl substituents and, conversely, with repulsive NCIs when the phenol has no aryl ortho substituents. Energetic span analysis is deployed to relate the observed NCI and the cycloreversion metathesis step such that aryloxide ligands with no ortho aryls mainly impact the energy of metallacyclobutane intermediates (SP/TBP isomers), whereas aryloxides with pendant ortho aryls influence the transition state energy for the cycloreversion step. While the electronic effects from the aryloxide ligands also play a role, our work outlines how NCIs may be exploited for the design of improved d0 metathesis catalysts.

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A solution-phase combinatorial approach based on the Ugi four-component reaction was implemented for the development of new prolyl peptide-peptoid hybrid catalysts. Three different elements of diversity were varied during the creation of the set of catalysts: the amine, oxo, and isocyano components. The multicomponent nature of this process enabled the straightforward generation of a series of peptide-peptoid hybrids having the generic sequence Pro-N-R(1)-Xaa-NHR(3), with Xaa being either Gly (R(2) = H) or Aib (R(2) = gem-Me) and R(1) and R(3) either alkyl or amino acid substituents. The catalytic behavior of the peptide-peptoid hybrids was assessed in the asymmetric conjugate addition of aldehydes to nitroolefins, where most of the catalysts showed great efficacy and rendered the Michael adducts with good to excellent enantio- and diastereoselectivity. A molecular modeling study was performed for two distinct catalysts aiming to understand their conformational features. The conformational analysis provided important information for understanding the remarkable stereocontrol achieved during the organocatalytic transformation.

Evidence for C-H···π(CuCl···HNCS) interactions, i.e. C-H···π(quasi-chelate ring) where a six-membered quasi-chelate ring is closed by an N-H···Cl hydrogen bond, is presented based on crystal structure analyses of (Ph3P)2Cu[ROC(=S)N(H)Ph]Cl. Similar intramolecular interactions are identified in related literature structures. Calculations suggest that the energy of attraction provided by such interactions approximates 3.5 kcal mol(-1).

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We have investigated the electronic impact of the R protecting group (TBS or PMB) in the conformational equilibrium of alpha-methyl substituted alcohols 1 (R = TBS) and 2 (R = PMB). The conformational analysis and (1)H NMR experiments for alcohols 1 and 2 reflect the tendency for the existence of hydrogen-bonded conformations. The intrinsic low basicity of silyl ethers does not affect the capacity of the oxygen attached to the silicon atom in forming intramolecular hydrogen bonds. We showed that the extents of the hydrogen bonds in silyl and alkyl ethers are determined by several properties, such as orbital interactions, lone pair hybridizations, and lone pair energies, and not just by the electronic occupancy of the donor atom. The populational analysis of NBO allowed understanding the intra- and intermolecular hydrogen bonds between the OH group and oxygen bonded to silicon as well as to alkyl ethers, concluding that there are distinct lone pair contributions.