Bromamine-T as an efficient amine source for Sharpless asymmetric aminohydroxylation of olefins

Asymmetric aminohydroxylation of various olefins was carried out using bromamine-T as nitrogen source in the presence of (DHQ)₂PHAL ligand. The new nitrogen source has been found to be effective in terms of yield and reaction time. The optical purities of the products could be obtained with up to 99% ee.     

Generation of exact analytic bound state solutions from solvable non-powerlaw potentials by a transformation method

A transformation method has been applied to the exactly solvable Hulthen problem to generate a hierarchy of exactly solved quantum systems in any chosen dimension. The generated quantum systems are, in general, energy-dependent with a single normalized eigenfunction, as the Hulthen potential is a non-powerlaw potential. A method has been devised to convert a subset of the generated quantum systems with energy-dependent potentials to a single normal system with an energy-independent potential that behaves like a potential qualitatively similar to the Poschl-Teller potential. A second-order application of the transformation method on the Hulthen system produces another Sturmian quantum system and a different method is given to regroup them into a normal quantum system which resembles the Morse potential. Existence of normalizable eigenfunctions for these systems are found to be dependent on the local and asymptotic behaviour of the transformation function. Received 30 August 2000 and Received in final form 16 March 2001     

Bakers' Yeast–Catalyzed Ring Opening of Benzofuroxans: An Efficient Green Synthesis of Aryl-1,2-diamines

A simple and inexpensive method for the reductive cleavage of N–O bond of benzofuroxans with bakers' yeast under nonfermenting condition in aqueous media was achieved. The procedure gives excellent yields of aryl-1,2-diamines.     

Concerted and stepwise proton-coupled electron transfers in aquo/hydroxo complex couples in water: oxidative electrochemistry of [Os(II)(bpy)(2)(py)(OH(2))](2+)

Successive oxidation of transition metal(II) aqua complexes (M(II)OH(2) to M(III)OH) is a domain in which proton-coupled electron transfer reactions are extremely common. The mechanism of these PCET reactions-concerted or stepwise-is an important issue in the understanding and design of natural or artificial systems catalyzing the formation of dioxygen by four-electron oxidation of water. Concerted proton-coupled electron transfer from an aqua metal(II) to a hydroxo metal(III) complex requires the close proximity of a proton-accepting group with a pK value between those of the aqua complexes. Otherwise, stepwise electron-proton or proton-electron pathways involving high-energy intermediates are followed. Concerted proton-electron pathways involving water as proton-acceptor or proton-donor group are inefficient. Cyclic voltammetry of the title complex in buffered aqueous solution and re-examination of previous results for the same complex attached to an electrode surface are used to establish these conclusions, which provide a starting point on the route to higher degrees of oxidation, such as those involved in the catalysis of water oxidation.     

Intramolecular 1,3-dipolar cycloaddition reactions in the synthesis of complex annelated quinolines, α-carbolines and coumarins

In this study, we report the synthesis of several novel dihydroisoxazole-, tetrahydroisoxazole- and dihydropyrazole-fused pyrido[2,3-b]quinolines, α-carbolines, and pyrido[2,3-c]coumarins, respectively, from simple precursors and by exploring intramolecular 1,3-dipolar cycloaddition reactions involving nitrile oxides, nitrones, and nitrile imines as 1,3-dipoles.     

A simple and efficient tetradentate Schiff base derived palladium complex for Suzuki–Miyaura reaction in water

A simple and efficient catalytic system based on Pd complex of tetradentate Schiff base ligands is found to be highly active (up to 99% isolated yield) for Suzuki–Miyaura reaction of aryl bromides with arylboronic acids in water at room temperature. Further the scope of this protocol has been extended to the Suzuki–Miyaura cross-coupling reaction of aryl chlorides with arylbronic acids in isopropanol.     

Pluronic F-127: An Efficient Delivery Vehicle for 3-(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH or Photochlor)

To determine the impact of delivery vehicles in photosensitizing efficacy of HPPH, a hydrophobic photosensitizer was dissolved in various formulations: 1% Tween 80/5% dextrose, Pluronic P-123 and Pluronic F-127 in 0.5%, 1% and 2% phosphate buffer solutions (PBS). HPPH was also conjugated to Pluronic F-127, and the resulting conjugate (PL-20) was formulated in PBS. Among the different delivery vehicles, only Pluronic P-123 displayed significant vehicle cytotoxicity, whereas Pluronic F127 was nontoxic. Compared to PL-20, HPPH formulated in Tween80 and Pluronic F-127 showed higher cell-uptake, but lower long-term retention in Colon26 cell compared to PL-20. The higher retention of PL-20 was similarly observed during in vivo uptake with BALB/c mice baring Ct26 tumors. In contrast to the in vitro uptake experiments, PL-20 showed slightly higher uptake compared to HPPH formulated in Tween or Pluronic-F127. A significant difference in pharmacokinetic profile was also observed between the HPPH-Pluronic formulation and PL-20. Under similar in vivo treatment parameters (drug dose 0.47 µmol kg⁻¹, light dose: 135 J cm⁻² at 24 h post-injection of PS), HPPH formulated either in Tween or Pluronic F-127 formulation showed similar in vivo PDT efficacy (20–30% tumor cure on day 60), whereas PL-20 showed 40% tumor cure (day 60).