Investigation of the titanium-mediated catalytic enantioselective oxidation of aryl benzyl sulfides containing heterocyclic groups.

Our enantioselective oxidation protocol, based upon hydroperoxides in the presence of a titanium/(,)-hydrobenzoin catalyst, was tested for the first time with aryl benzyl sulfides containing heterocyclic moieties (2-thienyl, 2-pyridyl and benzimidazolyl), two of them being connected with the blockbuster omeprazole drug. Good yields of enantiopure sulfoxides were obtained in most cases. Two exceptions of unsatisfactory enantioselectivity in the oxidation of benzimidazolyl sulfides are reported.

A comparative screening of laccase-mediator systems by white-rot fungi laccases for biocatalytic benzyl alcohol oxidation.

Production of value-added compounds from waste materials is of utmost importance for the development of a sustainable society especially regarding their use as catalysts in industrially relevant synthetic reactions. Herein, we show the production of laccases from four white-rot fungi, which were grown on agricultural residues, specifically Trametes versicolor 11269, Pleurotus ostreatus 1020, Panus tigrinus 707 and Lentinula edodes SC-495. The produced laccases were tested on a laccase-mediator system (LMS) for the biocatalytic oxidation of the model substrate benzyl alcohol into benzaldehyde.

Structural insights into methyl- or methoxy-substituted 1-(α-aminobenzyl)-2-naphthol structures: the role of C-H...π interactions.

Aminobenzylnaphthols are a class of compounds containing a large aromatic molecular surface which makes them suitable candidates to study the role of C-H...

Stereochemical analysis of β-keto sulfoxides by circular dichroism.

Three β-keto sulfoxides (1-3) were synthesized in enantiopure form and investigated by means of circular dichroism (CD) spectroscopy, both in electronic and vibrational range (ECD, VCD), in combination with quantum chemical calculations. For compound 2, the X-ray structure was available; thus, the ECD in the solid state was also considered to reveal the differences between the molecular species in both states. Despite the simplicity of all β-keto sulfoxides under investigation (29 atoms), reproducing even the major spectral VCD features failed for two compounds, making the use of VCD not ideal to assign their absolute configuration in a reliable way.

Asymmetric chemoenzymatic synthesis of 1,3-diols and 2,4-disubstituted aryloxetanes by using whole cell biocatalysts.

Regio- and stereo-selective reduction of substituted 1,3-aryldiketones, investigated in the presence of different whole cell microorganisms, was found to afford β-hydroxyketones or 1,3-diols in very good yields (up to 95%) and enantiomeric excesses (up to 96%). The enantiomerically enriched aldols, obtained with the opposite stereo-preference by baker's yeast and Lactobacillus reuteri DSM 20016 bioreduction, could then be diastereoselectively transformed into optically active syn- or anti-1,3-diols by a careful choice of the chemical reducing agent (diastereomeric ratio up to 98 : 2). The latter, in turn, were stereospecifically cyclized into the corresponding oxetanes in 43-98% yields and in up to 94% ee, thereby giving a diverse selection of stereo-defined 2,4-disubstituted aryloxetanes.

Stacked naphthyls and weak hydrogen-bond interactions govern the conformational behavior of P-resolved cyclic phosphonamides: a combined experimental and computational study.

P-Enantiomerically pure cyclic phosphonamides have been synthesized via a cyclization reaction of (S,S)-aminobenzylnaphthols with chloromethylphosphonic dichloride. The reaction is highly stereoselective and gives almost exclusively (S,S,SP)-cyclic phosphonamides in good yields. Analysis of the X-ray crystal structures shows clearly that the cyclization reaction forces the two naphthyl rings into a stable parallel displaced stacking assembly and indicates also the existence of intramolecular CH···π interactions and weak forms of intermolecular hydrogen bondings, involving the oxygen and the chlorine atoms.

Bioactivity of a family of chiral nonracemic aminobenzylnaphthols towards Candida albicans.

Chiral nonracemic aminobenzylnaphthols were obtained by a Betti multi-component reaction between 2-naphthol, aryl aldehydes and enantiopure arylethylamine. Moreover, some new aminobenzylnaphthols were synthesized by a similar reaction between 2-naphthol, aryl aldehydes and prolinol. These aminobenzylnaphthols, synthesized from different components and thus having different structural features, were tested as anti-yeast agents inhibiting Candida albicans.

Strong intermolecular exciton couplings in solid-state circular dichroism of aryl benzyl sulfoxides.

A series of 13 enantiopure aryl benzyl sulfoxides () with different substituents on the two aromatic rings has been previously analyzed by means of electronic circular dichroism (CD) spectroscopy. Most of these compounds are crystalline and their X-ray structure is established. For almost one-half of the series, CD spectra measured in the solid state were quite different from those in acetonitrile solution.

Systematic investigation of CD spectra of aryl benzyl sulfoxides interpreted by means of TDDFT calculations.

The CD spectra of 13 crystalline aryl benzyl sulfoxides 1a-m with various substituents on the two aromatic rings were recorded in solution and in the solid state. Solution CD spectra were very homogeneous along the series, consisting in most cases of a couplet-like feature in the 200-300 nm region. The red-shifted component of the couplet, corresponding to the sulfoxide-centered n-pi* transition, is always positive for (R) absolute configuration in accordance with Mislow's rule.

A combined theoretical and experimental investigation on the enantioselective oxidation of aryl benzyl sulfides in the presence of a chiral titanium catalyst.

An experimental investigation of the enantioselective oxidation of aryl benzyl sulfides by tert-butyl hydroperoxide in the presence of a titanium/hydrobenzoin catalyst has shown that these sulfides are ideal substrates for this catalytic system, with negligible interference by the substituents on the aryl groups. A reaction mechanism based on DFT computations has been proposed. The DFT MPWB1K functional was used in the theoretical investigation to account for weak hydrogen-bonding and pi interactions.

Catanionic systems from conversion of nucleotides into nucleo-lipids.

This article focuses on reactions performed in nanostructured environments where the pair of complementary nucleotides, 5'-AMP and 5'-UMP, are converted into their amphiphilic derivatives. The synthesis is carried out by using the hydrophobic reactant dodecyl epoxide (DE) dispersed in a micellar solution based on the cationic surfactant cetyltrimethylammoniumbromide (CTAB). Novel nucleo-lipids monomers and CTAB molecules give rise to the spontaneous self-assembly of catanionic supramolecular structures in water, showing typical Maltese crosses in optical microscopy.

Platinum complexes can inhibit matrix metalloproteinase activity: platinum-diethyl[(methylsulfinyl)methyl]phosphonate complexes as inhibitors of matrix metalloproteinases 2, 3, 9, and 12.

Platinum complexes able to inhibit matrix metalloproteinases (MMPs) through a noncompetitive mechanism are reported for the first time in this study. [PtCl2(SMP)] and [Pt(dimethylmalonato)(SMP)], characterized by the bisphosphonate-analogue ligand diethyl[(methylsulfinyl)methyl]phosphonate (SMP), are slight inhibitors of MMP-2 (IC50 = 258 +/- 38 and 123 +/- 14 microM, respectively) but markedly inhibit MMP-9 (IC50 = 35.5 +/- 6 and 17 +/- 4 microM), MMP-3 (IC50 = 5.

A straightforward enantioselective route to dialkyl sulfoxides based upon two carbon-for-carbon substitution reactions on the sulfinyl group.

Benzyl p-bromophenyl sulfoxide 1 was obtained on a multigram scale and in an enantiomerically pure form by an enantioselective catalytic oxidation, using tert-butyl hydroperoxide in the presence of chiral titanium complexes. Some mechanistic and stereochemical features of interest were studied in this process. Compound 1 was then subjected to two different substitution reactions with Grignard reagents, which caused two sequentially stereocontrolled carbon-for-carbon displacements, leading to chiral nonracemic dialkyl sulfoxides.