Synthesis of 6,6′- and 6-MeO–PEG–BINOL-Ca soluble polymer bound ligands and their application in asymmetric Michael and epoxidation reactions

Design and synthesis of a flexible spacer attached 6-MeO–PEG–BINOL ligand has been described. The enantioenriched Ca soluble polymer bound ligand (SPB-II) was generated utilizing easily available, eco-friendly CaCl₂, and applied for CC as well as CO bond forming reactions. The ligand was precipitated adding diethylether, and the same ligand was used with equal efficiency for two more cycles.     

Hydroxy-rhodium(I) catalyzed regioselective Michael addition of cyclic enones

Hydroxy-rhodium catalyzed dimerization of various cyclic enones to the corresponding α-enone adducts is developed. The key feature of this method is that the base-sensitive, highly substituted enones also undergo dimerization and the resultant products are obtained in moderate to good yields.     

Enantioselective synthesis of cyclopropyl δ-lactonealdehydes and dodecyl-5-ene-1-yne-3-ol: advanced intermediates of solandelactone A and B

A stereocontrolled synthesis of cyclopropyl δ-lactonealdehydes and dodecyl-5-ene-1-yne-3-ol is accomplished with predictable absolute stereochemistry via organocatalytic and catalytic asymmetric transfer hydrogenation reactions. The salient feature of this protocol is the genesis of chirality through an organocatalytic reaction and utilized for installing a critical bifunctional trans-cyclopropane motif, which is a key segment of every representative member of the oxylipin class of natural products such as solandelactone A and B.     

Low field AC susceptibility study of intergranular critical current density in Mg-substituted CuBa2Ca3Cu4O12−y high temperature superconductors

Measurements of the a.c.susceptibility (χ=χ′+iχ″) have been made on the Mg substituted high T_C superconducting system, CuBa₂(Mg_xCa_1−x)₃Cu₄O_12−y (Cu-1234) with x=0, 0.10 & 0.20, at different values of the a.c.field amplitude. Estimates of the intergranular critical current density(J_C) made from the field dependent χ″-T curves show an improvement in the Mg-substituted Cu-1234 system. Results have been analysed in the light of the crystal structure and the superconducting anisotropy factor (γ=ξ_ab/ξ_c) of the Cu-1234 system. Lower superconducting anisotropy emanating from Mg substitution has been found to be significant, resulting in better superconducting properties.     

HPMA copolymer-doxorubicin-gadolinium conjugates: synthesis, characterization, and in vitro evaluation

This study describes the synthesis, characterization, and in vitro evaluation of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-gadolinium (Gd)-doxorubicin (Dox) conjugates. Copolymers of HPMA were derivatized to incorporate side chains for Gd chelation and Dox conjugation. The conjugates were characterized by their side chain contents, T(1) relaxivity (r(1)), stability, and in vitro cytotoxicity. High stability and relaxivity of these conjugates coupled with low toxicity show their potential for monitoring the in vivo fate of HPMA-based drug delivery systems by magnetic resonance imaging techniques.     

Enantioselective total synthesis of eicosanoid and its congener, using organocatalytic cyclopropanation, and catalytic asymmetric transfer hydrogenation reactions as key steps

An enantioselective unified strategy for the syntheses of the oxylipin class of natural products was accomplished. Our strategy relies on three catalytic steps: (a) organocatalytic cyclopropanation, (b) the catalytic asymmetric transfer hydrogenation (CATHy) reaction, and (c) the Nozaki-Hiyama-Kishi reaction.     

Pathway to copolymer collapse in dilute solution: uniform versus random distribution of comonomers

Monte Carlo simulations show that copolymers with uniformly (or periodically) distributed sticky comonomers collapse "cooperatively," abruptly forming a compact intermediate comprising a monomer shell surrounding a core of the aggregated comonomers. In comparison, random copolymers collapse through a relatively less-compact intermediate comprising a comonomer core surrounded by a fluffy monomer shell that densifies over a wide temperature range. This difference between the collapse pathways for random and uniform copolymers persists to higher chain lengths, where uniform copolymers tend to form multiple comonomer cores. In this paper, we describe the formation of such an intermediate state, and the subsequent collapse, by recognizing that these arise from the expected balance between comonomer aggregation enthalpy and loop formation entropy dictated by the chain microstructure.     

Design,synthesis, and biological evaluation of novel substituted imidazo[2,1-a]isoindole derivatives as antibacterial agents

An efficient protocol has been developed for the synthesis of fused imidazo[2,1-a]isoindol-5-ones (2a–d) from 2-iodo benzoic acids and N,N-carbonyldiimidazole (CDI) using one-pot Pd-catalyzed C?C bond coupling. The reaction of imidazo[2,1-a]isoindol-5-one (2a–d) with substituted α-bromo ketones in toluene afforded corresponding imidazo[2,1-a]isoindolium derivatives (3a–i) in good yields. The structures of the title compounds were well established on the basis of infrared (IR), ¹H NMR, carbon-13 nuclear magnetic resonance (¹³C NMR), mass spectral data, and elemental analysis (C, H, and N). In vitro antibacterial results revealed that, the compounds 3b and 3i were found to possess an excellent broad spectrum of inhibiting potency against all the tested bacterial strains with minimum inhibitory concentration values ranging from 3.125 to 25?µg mL^?1.     

Highly Enantioselective Synthesis of Orthogonally Protected (2S)‐2,3‐Diaminopropanoates through Catalytic Phase‐Transfer Aza‐Henry Reaction

The syntheses of enantiomer‐enriched orthogonally protected different (2S)‐2,3‐diaminopropanoates and unnatural furyl‐substituted (tert‐butoxy)carbonyl (Boc) as well as (benzyloxy)carbonyl (Cbz) protected amino acid esters are accomplished by means of an enantioselective aza‐Henry reaction. A key feature of this protocol is organocatalysis as a genesis of chirality to ensure high enantioselectivity.