Synthesis, identification, chiral separation and crystal structure of (3R,4R,7S,8S)-3,4,7,8-tetrachlorodecane and its stereoisomers.

Chlorinated paraffins (CPs) are a notoriously known class of compounds that stand amongst the most wide-spread persistent organic pollutants. Therefore, their reliable, repeatable, and reproducible quantitative analysis using well-defined reference standards is of utmost importance. In view of the increasing demand for constitutionally and stereochemically defined CP standards, we have synthesized a stereoisomeric mixture of 3,4,7,8-tetrachlorodecane. One stereoisomer - (3R,4R,7S,8S)-3,4,7,8-tetrachlorodecane was separated from the mixture, and enriched fractions of residual stereoisomers were achieved through crystallisation of the residual mother liquors. The molecular structure of the single isolated stereoisomer was confirmed through single-crystal X-ray crystallographic data. One fraction of 3,4,7,8-tetrachlorodecane stereoisomers was successfully separated on a chiral stationary phase using supercritical fluid chromatography hyphenated to mass spectrometry (column: Chiral ART Amylose-C; mobile phase: CO2/MeOH (96/4 v/v) with 0.1% diethylamine). The reported separation of stereoisomers is unprecedented in CP analysis so far.

Nuclear magnetic resonance as a tool to determine chlorine percentage of chlorinated paraffin mixtures.

A new simple method for chlorine percentage calculations (method C), from proton nuclear magnetic resonance (1H NMR) spectroscopy, has been established and applied to an industrial chlorinated paraffin (CP) mixture and 13 single-chain CPs of known carbon chain lengths. Two modified methods (method A and B), originating from the work of Sprengel et al., have been utilized on the same single-chain mixtures. All samples were analysed by 1H NMR and two-dimensional heteronuclear quantum coherence (HSQC) for this purpose. All three methods worked well for medium chlorinated (45-55% Cl) single-chain mixtures of known carbon chain lengths. Method A yielded the best result for mixtures of lower chlorine content (<45% Cl), method C gave better estimations for higher chlorine contents (>55% Cl). Compared to Mohr's titration, method A showed a deviation of 0.7-7.8% (3.6% average), method B 4.1-11.3% (7.0% average) and method C 0.6-11.6% (5.2% average), for all 13 single-chain mixtures. The new method C is the only method that could be applied for determining the chlorine percentage of industrial mixtures of multiple, unknown chain lengths.

Syntheses and anti-tubercular activity of ß-substituted and α,ß-disubstituted peptidyl ß-aminoboronates and boronic acids.

Tuberculosis is still affecting millions of people worldwide, and new resistant strains of Mycobacterium tuberculosis are being found. It is therefore necessary to find new compounds for treatment. In this paper, we report the synthesis and in vitro testing of peptidyl ß-aminoboronic acids and ß-aminoboronates with anti-tubercular activity.

Boron-containing peptidomimetics--a novel class of selective anti-tubercular drugs.

Medical treatment for tuberculosis is complicated nowadays by the appearance of new multiresistant strains, and therefore, new antibiotics are in great need. Here, we report the synthesis and in vitro testing of a new class of highly selective antimicrobial boron-containing peptidomimetics with compounds exhibiting activity against Mycobacterium tuberculosis at ≤5 µg/mL. The new approach developed makes it possible to synthesize variously substituted ß-aminoboronic acids and their derivatives with a high level of diastereoselectivity.

Potassium [(1S)-1-azido-2-phenyl-eth-yl]trifluorido-borate.

The title compound, K(+)·C(8)H(8)BF(3)N(3) (-), is a salt containing the chiral organic trifluorido-borate anion. The organic anions and potassium cations are tightly bound to each other by the coordination K-F [2.654 (3)-3.102 (3) Å] and K-N [2.951 (4)-3.338 (4) Å] inter-actions. Thus, the potassium cation adopts a nine-vertex coordination polyhedron, which can be described as a distorted monocapped tetra-gonal anti-prism. In the crystal, the organic anions and potassium cations form layers parallel to (001). Weak C-H⋯π inter-actions between neighbouring phenyl rings further stabilize the crystal.