New di‐ and triorganotin(IV) carboxylates derived from a Schiff base: synthesis,characterization and in vitro antimicrobial activities

A new carboxylic acid, 2‐{[5‐(2‐nitrophenyl)furan‐2‐yl]methyleneamino}benzoic acid (HOBZ), has been produced by reacting 5‐(2‐nitrophenyl)furfural with 2‐aminobenzoic acid. Reactions of NaOBZ with organotin chlorides led to formation of [Me₃Sn(OBZ)] ( 1 ), [Bu₃Sn(OBZ)] ( 2 ), [Me₂Sn(OBZ)₂] ( 3 ) and [Bu₂Sn(OBZ)₂] ( 4 ). Complexes 1 , 2 , 3 , 4 have been characterized using elemental analyses and infrared, ¹H NMR, ¹³C NMR, ¹¹⁹Sn NMR and ¹¹⁹Sn Mössbauer spectroscopies. In the solid state, the OBZ ligands might coordinate to tin in an anisobidentate fashion via the carboxylate group. The in vitro antimicrobial activity of all compounds has been screened against the following fungi: Aspergillus niger, A. flavus, A. parasiticus, Penicillium citrinum, Candida dubliniensis, C. lusitaniae, C. albicans, C. tropicalis, C. parapsilosis and C. glabrata; and against the following bacteria: Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Streptococcus sanguinis, Escherichia coli, Citrobacter frendii, Salmonella typhimurium and Pseudomonas aeruginosa. Complexes 2 and 4 exhibited higher biocide activity in comparison to 1 and 3 and to the control drugs nystatin and miconazole nitrate for the yeasts, and chloramphenicol and ampicillin for the bacteria. The biological activity of 2 was superior to that of 4 . In addition, the toxicity of HOBZ, NaOBz and 1 , 2 , 3 , 4 were determined using Chlorella vulgaris, revealing low toxicity of the complexes at MIC₅₀ concentrations. We also performed cell viability studies, using XTT assay, displaying no change in the mitochondrial function after 2–4 h of exposure of the microorganism to the complexes at MIC₅₀ concentrations. The butyl‐containing complexes 2 and 4 display greater lipophilicities than do the methyl analogues 1 and 3 , thereby endowing 2 and 4 with superior abilities to cross the microbe cell membrane, the possible mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd.     

Isomerizing Olefin Metathesis

Isomerizing olefin metathesis is currently undergoing a transformation from laboratory curiosity to powerful synthetic concept at the heart of orthogonal tandem catalysis. In this process, an isomerization catalyst continuously moves double bonds along carbon chains, while a metathesis catalyst scrambles the residues at the C−C double bonds. This cooperative action of two catalysts can be used to access single, defined products from a complex mixture of compounds. Alternatively, it enables the transformation of uniform starting materials into complex product blends with defined, tunable properties. This concept article highlights recent developments and potential applications of this fascinating reaction concept.     

Structure of 2,2′-anhydro-3′-O-acetyl-2′thio-1-β-D-arabinofuranosylcytosine hydrochloride1

2,2-Anhydro-3-O-acetyl-2-thio-1--D-arabinofuranosylcytosine hydrochloride crystallizes in space group P2₁2₁2₁ witha=10.373(1),b=14.517(2),c=9.496(1) Å. Reflections were measured on a diffractometer and the structure was solved by direct methods. Least-squares refinement converged atR=0.056 andR _w =0.063. The study of this crystal structure showed that the alterations in the geometry of 2,2-anhydro-1--D-arabinofuranosylcytosine when the bridge oxygen is replaced by sulfur are localized in the region of the fused ring. The angle at the bridge atom decreases to nearly 90°, with concomitant enlargements of about 5°–7° in the angles opposite to the bridge atom. Angle C(1)-N(1)-C(6) decreases by 4°. Also, the amount of double bond character in the bond formed by C(2) and the bridge atom decreases. A survey of the conformational features of S,2-cyclonucleosides and comparison with O,2-cyclonucleosidcs showed that their preferred conformations are the same. However, S,2-cyclonucleosides exhibit a wider range of P and values. This correlates with a greater ease of the sulfur containing five-membered ring to pucker as compared to the oxygen-cyclo ring.This paper is part of the authors' dissertation (Vitali, 1986).     

Synthesis of the C(26)-C(42) and C(43)-C(67) pyran-containing fragments of amphidinol 3 via a common pyran intermediate

The pyran-containing fragments 1 and 2 of AM3 have been synthesized from the common pyran intermediate 3. Careful orchestration of the alcohol protecting groups was necessary to facilitate deprotection of alcohol functionality in the presence of the chemically sensitive polyene chain.     

Orientational disorder in 4‐chloronitrobenzene

The crystal structure of 4‐chloronitrobenzene, C₆H₄ClNO₂, a material that exhibits disorder in the solid state, is re‐examined using multiple‐temperature single‐crystal X‐ray diffraction. Our results show a marked improvement on previous crystal structure determinations and our comprehensive multiple temperature measurements help to rationalize the structural anomalies. 4‐Chloronitrobenzene exhibits twofold orientational disorder of the NO₂/Cl substituents, with the molecule lying across an inversion centre. There is also evidence of large thermal motion, which exists at all temperatures and reflects the presence of significant disorder in this material. The nitro group shows possible libration, with one O atom exhibiting larger thermal motion than the other across the whole temperature range. This is explained by a difference in hydrogen‐bonding environment.     

Convenient method for the rapid generation of highly active and enantioselective yttrium catalysts for asymmetric hydroamination

A facile method for the preparation of highly active and enantioselective yttrium precatalysts for asymmetric hydroamination of gem-disubstituted aminoalkenes, from the combination of YCl(3) or YCl(3)(THF)(3.5) with ligand (R)- and n-BuLi is described.     

NMR and X-ray diffraction analysis of 3-thioamido-5-phosphono-1-cyclohexene derivatives: Conformational and stereochemical assignments

Reaction of N-(dienyl)-4-(R)-phenyloxazolidin-2-thione (1) with 1-diethoxyphosphoryl-1-buten-3-one (2a), methyl 3-(diethoxyphosphoryl)acrylate (2b) and 3-(diethoxyphosphoryl)acrylonitrile (2c) furnished the [4 + 2] cycloadducts 3a, 3b and 3c, respectively, as single stereoisomers, confirming the efficiency of the oxazolidin-2-thione chiral auxiliary in the facial discrimination of Diels–Alder reactions. The absolute configuration of the 3,4,5-trisubstituted cyclohexene derivatives (3a–c) was established by X-ray diffraction analysis. NMR studies confirmed the relative stereochemistries and showed two possible conformers in solution.