ABSTRACT
1-Butyl-3-methylimidazolium chloroaluminate ionic liquids have been employed as an unconventional reaction media and as Lewis acid catalyst for Friedel-Crafts sulfonylation reaction of benzene and substituted benzenes with 4-methyl benzenesulfonyl chloride. The substrates exhibited enhanced reactivity, furnishing almost quantitative yields of diaryl sulfones, under ambient conditions. Studies concerning the effect of Lewis acidity of the ionic liquid on the initial extent of conversion of this reaction has been carried out. (27)Al NMR spectroscopy has been exploited as a tool to investigate the mechanistic details of the reaction. (27)Al NMR spectral studies show the predominance of [Al(2)Cl(7)](-) species in [bmim]Cl-AlCl(3), N = 0.67, acidic ionic liquid in the presence of 4-methyl benzenesulfonyl chloride, and after the reaction with the aromatic hydrocarbon, [AlCl(4)](-) species predominates. This change in speciation of aluminum can be attributed to the interaction of the Lewis acidic species [Al(2)Cl(7)](-) of the ionic liquid with the formed HCl during the sulfonylation reaction, which is evidenced by the control experiment. Preliminary investigations on Friedel-Crafts acylation further substantiate the argument.
ABSTRACT
Resolution of (R)- and (S)-dropropizine which is an antitussive and central sedative therapeutic agent in high optical and chemical yields was achieved by lipases of Pseudomonas cepacia supported on ceramic particles (lipase PS-C) and on diatomite (lipase PS-D) with oxime esters in organic solvents. The influence of several factors (lipase source, structural variations in oxime esters, the amount of lipase and its recyclability) on the enantioselectivity have been investigated. Different properties were used to describe the solvents, namely the hydrophobicity (quantified by log P) and the dielectic constant (epsilon). This enzymatic acylation using oxime esters was significant as only (S)-dropropizine and (R)-dropropizine monoacetate was obtained. (R)-Dropropizine monoacetate was chemically hydrolyzed to obtain (R)-dropropizine. The highest enantioselectivity was observed when O-acetyl benzophenone oxime was used. This enzymatic resolution provides a versatile method for getting the pure enantiomers of dropropizine by effectively optimizing the various reaction parameters.
ABSTRACT
(+/-)-Atenolol/(+/-)-propranolol and their acetates were incubated with the fungus Rhizopus arrhizus and Geotrichum candidum separately for different time intervals to afford (S)-atenolol/(S)-propranolol in good optical yield. The time and pH for this biotransformation was optimised. The present biodegradations using Rhizopus arrhizus and Geotrichum candidum provides a simple and useful method to obtain (S)-atenolol and (S)-propranolol which are active enantiomers of the beta-adrenergic blockers.
Subject(s)
Adrenergic beta-Antagonists/chemistry , Atenolol/chemistry , Geotrichum/metabolism , Propranolol/chemistry , Rhizopus/metabolism , Adrenergic beta-Antagonists/metabolism , Atenolol/metabolism , Biodegradation, Environmental , Biotransformation , Geotrichum/chemistry , Hydrogen-Ion Concentration , Molecular Conformation , Molecular Structure , Propranolol/metabolism , Rhizopus/chemistry , Stereoisomerism , Time FactorsABSTRACT
A new approach to the liquid phase synthesis of oligonucleotide is described, it is based on oxidative coupling using alkyl H-phosphonate synthon and polyethylene glycol (PEG5000) as a soluble support. Nucleoside alkyl H-phosphonate undergoes oxidative coupling in presence of NBS. The use of polyethylene glycol as a soluble polymeric support preserves some convenient features of the solid phase synthesis with new interesting advantages. This liquid phase method appears effective in terms of speed and coupling yield and can be evaluated for the production of large amount of oligonucleotide (100 microM).
Subject(s)
Oligonucleotides/chemical synthesis , Organophosphonates/chemistry , Base Sequence , Magnetic Resonance Spectroscopy , Oxidation-ReductionABSTRACT
A new chelating ion-exchange resin with a spacer CH(2)-NH-C(6)H(4)- based on a microreticular chloromethylated styrene-divinylbenzene copolymer containing alpha-nitroso-beta-naphthol as a functional group has been synthesized. The sorption characteristics for manganese(II), iron(III), cobalt(II), nickel(II), copper(II), and zinc(II) have been investigated over the pH range 1.0-7.0. The resin is highly stable in acidic and alkaline medium. Iron(III) and cobalt(II); copper(II) and iron(III) are separated very effectively in a column operation by stepwise elution.
