Solid‐state tautomeric structure and invariom refinement of a novel and potent HIV integrase inhibitor

The conformation and tautomeric structure of (Z)‐4‐[5‐(2,6‐difluorobenzyl)‐1‐(2‐fluorobenzyl)‐2‐oxo‐1,2‐dihydropyridin‐3‐yl]‐4‐hydroxy‐2‐oxo‐N‐(2‐oxopyrrolidin‐1‐yl)but‐3‐enamide, C₂₇H₂₂F₃N₃O₅, in the solid state has been resolved by single‐crystal X‐ray crystallography. The electron distribution in the molecule was evaluated by refinements with invarioms, aspherical scattering factors by the method of Dittrich et al. [Acta Cryst. (2005), A 61 , 314–320] that are based on the Hansen–Coppens multipole model [Hansen & Coppens (1978). Acta Cryst. A 34 , 909–921]. The β‐diketo portion of the molecule exists in the enol form. The enol –OH hydrogen forms a strong asymmetric hydrogen bond with the carbonyl O atom on the β‐C atom of the chain. Weak intramolecular hydrogen bonds exist between the weakly acidic α‐CH hydrogen of the keto–enol group and the pyridinone carbonyl O atom, and also between the hydrazine N—H group and the carbonyl group in the β‐position from the hydrazine N—H group. The electrostatic properties of the molecule were derived from the molecular charge density. The molecule is in a lengthened conformation and the rings of the two benzyl groups are nearly orthogonal. Results from a high‐field ¹H and ¹³C NMR correlation spectroscopy study confirm that the same tautomer exists in solution as in the solid state.     

Bromine Complexes of Polyvinylpyrrolidone Supports: A Mild Reagent for the Transformation of α‐Oxoketene Dithioacetals to β‐Oxothiolesters

When α‐oxoketene dithioacetals 1a–n were treated with the bromine complex of a copolymer of 1‐vinyl‐2‐pyrrolidone and 4‐vinylpyridine, the corresponding thiolcarboxylates 2a–n were formed in excellent yields. The reaction also works with other 1‐vinyl‐2‐pyrrolidone‐derived polymers as well as commercially available polyvinylpyrrolidone–bromine complexes. The method is suitable for preparing aliphatic, aromatic, and γ,δ‐unsaturated β‐oxothiolcarboxylates.     

Personal Sun Exposure and Serum 25‐hydroxy Vitamin D Concentrations

Solar ultraviolet‐B radiation (UVB) is essential for epidermal vitamin D production. We aimed to quantitate the relationship between personal solar UV exposure and serum 25hydroxy vitamin D (25[OH]D) concentration. Blood was collected for 25(OH)D analysis in 207 South Australian adults aged 27–61 years. At the time of blood collection, each participant completed a questionnaire, which included a calendar for recall of sun exposure in the preceding 16 weeks. We examined the association between solar UV exposure and serum 25(OH)D graphically from smoothed scatter plots, and modeled it using multiple linear regression, with age, sex and body mass index as covariates. Estimated erythemal solar UV exposure in the 6 weeks before blood collection best predicted serum 25(OH)D concentrations. Serum 25(OH)D rose with increasing personal solar UV exposure to a maximum of about 89 nmol L^?1 at an estimated mean weekly solar erythemal UV exposure of about 1230 mJ cm^?2. The maximum was the same after accounting for clothing coverage and was reached at an estimated whole body equivalent exposure to ambient UV of ca 700 mJ cm^?2. These results suggest that an average maximum serum 25(OH)D of ca 89 nmol L^?1 is achieved from sun exposure in a healthy Australian adult population.     

Montmorillonite K-10 Clay Catalysed Glycosidation of 1-O-Acetyl-2,3-dideoxy-dl-pent-2-enopyrano-4-ulose

The O-glycosidation reaction of 1-O-acetyl-2,3-dideoxy-DL-pent-2-enopyran - 4 -ulose catalysed by the environmentally accepted and inexpensive industrial catalyst Montmorillonite K-10 clay with variety of alcohols in high yield is reported.     

Electro-disclinic effect in tilted smectic phases of banana-shaped liquid crystal materials

We give the first evidence that the director tilt angle can be reduced by electric fields in the tilted smectic phase of banana-shaped molecules. In these phases the value of polarization is determined by the molecular packing and no electro-clinic effect is expected. Our studies show that high electric fields eventually induce a meta-stable phase with zero director tilt. The tilted phase slowly recovers at low fields. We propose that the field-induced quenching of the layer fluctuations is responsible for the observed effects.     

Photoinduced phase transitions

Employing actinic light to alter/stabilise a particular thermodynamic phase via the photo-isomerisation of the constituent molecules is an interesting tool to investigate soft matter from a new dimension. This article focuses on our recent results on several aspects of these non-equilibrium phase transitions, which are isothermal in nature. We specifically discuss (i) the influence of different parameters, such as confinement, applied electric field, pressure etc., on the dynamics associated with both the photochemical transition driving the equilibrium nematic to the non-equilibrium isotropic phase and the thermal back relaxation recovering the nematic phase, (ii) unique light-driven disorder–order transition in a reentrant system, (iii) dynamic self-assembly of the smectic A phase, which is stabilised only in the presence of actinic light, (iv) novel temperature-intensity phase diagrams and an example of primary and secondary photo-ferroelectric effects in an antiferroelectric smectic C system. These results highlight the fact that the actinic light can be used as a new tool to study phase transitions and the associated critical phenomena that could also bring about effects that are not seen in equilibrium situations.     

S‐Alkylation of Soft Scorpionates

The alkylation reactions of soft scorpionates are reported. The hydrotris(S‐alkyl‐methimazolyl)borate dications (alkyl=methyl, allyl, benzyl), which were prepared by the reaction of Tm^Me anion and primary alkyl halides, have been isolated and structurally characterised. The reaction is, however, not universally successful. DFT analysis of these alkylation reactions (C?S versus B? H alkylation) indicates that the observed outcome is driven by kinetic factors. Extending the study to incorporate alternative imine thiones (mercaptobenzothiazole, bz; thiazoline, tz) led to the structural characterisation of di[aquo‐μ‐aquohydrotris(mercaptobenzothiazolyl)boratosodium], which contains sodium atoms in the κ³‐S,S,S coordination mode. Alkylation of Na[Tbz] and Na[tzTtz] leads to decomposition resulting in the formation of the simple S‐alkylated heterocycles. The analysis of the species involved in these reactions shows an inherent weakness in the B? N bond in soft scorpionates, which has implications for their use in more advanced chemistry.     

Synthesis of enantiopure furo[2,3-b]pyrroles

A simple method for the preparation of enantiopure furo[2,3-b]pyrroles, a rare class of concave bicyclic nitrogen and oxygen heterocycle, in promising yield has been developed. The 3-substituted pyrrolidinediones prepared from (2S,3S)-tetrahydro-3-hydroxy-5-oxo-2,3-furandicarboxylic acid (Garcinia acid) have been cyclized diastereo as well as enantioselectively to furo[2,3-b]pyrroles. The cyclization follows Baldwin’s rule.     

Hydrogen bonding interaction and topological insights of the electron localization/delocalization of l- arginine acetate

The vibrational spectral studies of the semi-organic material l- arginine acetate (LAA) are carried out with the help of density functional calculations to derive the equilibrium geometry as well as the vibrational wavenumbers and intensities of the spectral bands. The vibrational spectrum assignments are performed using normal coordinate analysis (NCA) in accordance with the scaled quantum mechanical force field approach (SQMFF). Vibrational spectra confirm the COO- modes split due to intra- and intermolecular association based on C–O….H, N–H….O, and O–H?O hydrogen bonding in the molecule, which lowers carboxylate wavenumbers. The natural bond orbital (NBO) analysis and DFT computations also confirm the occurrence of strong intra and intermolecular N–H?O and O–H?O ionic hydrogen bonding between charged species, providing the non-centrosymmetric structure in the LAA crystal.     

Allyl ether of aralkyl phenolic resin with low melt viscosity and its Alder‐ene blends with bismaleimide: synthesis,curing, and laminate properties

This paper outlines the synthesis and characterization of O‐allyl aralkyl phenolic (O‐allyl Xylok, OAX) resins having low melt viscosity and its Alder‐ene blends with 2, 2′‐bis 4‐[(4′‐maleimido phenoxy) phenyl] propane. The blends manifested a three‐stage curing pattern that converged to a two‐stage pattern on enhancing the maleimide content. The polymerization kinetics of typical allyl and maleimide rich resin systems showed apparent activation energy increasing and pre‐exponential factor decreasing from ene to the Diels–Alder step. Increased allyl content improved mechanical and impact properties of the composites at ambient temperature, although it diminished the retention of interlaminar shear strength at elevated temperature. Increased maleimide content of the resin was conducive for the higher rigidity for the composite and its retention at elevated temperature. A substantial increase in T_g (from 153°C to 280°C) and thermal stability was observed with an increase in maleimide content. High allyl content resulted in improved mechanical properties thanks to better resin–reinforcement interaction as revealed from morphological analysis. Copyright © 2014 John Wiley & Sons, Ltd.