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Reduction Sequence (reduction + sequence)
Selected AbstractsEnantioselective Synthesis of 4-(Dimethylamino)pyridines through a Chemical Oxidation-Enzymatic Reduction Sequence.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2006Application in Asymmetric Catalysis Abstract Enantiomerically pure 4-(dimethylamino)-3-(1-hydroxyalkyl)pyridines and 4-(dimethylamino)-3-[hydroxy(phenyl)methyl]pyridine have been prepared through efficient chemoenzymatic routes. For this purpose different lipases and oxidoreductases have been tested in the preparation of optically active 4-chloro derivatives and baker's yeast was found to be an excellent catalyst for the bioreductions of the corresponding ketones. Their applications as enantioselective nucleophilic catalysts have been studied, important catalytic properties were observed in the stereoselective construction of quaternary centers. [source] 1,4-Butanediol as a Reducing Agent in Transfer Hydrogenation ReactionsCHEMISTRY - AN ASIAN JOURNAL, Issue 3 2010Hannah Abstract 1,4-Butanediol is able to deliver two equivalents of H2 in hydrogen-transfer reactions to ketones, imines, and alkenes. Unlike simple alcohols, which establish equilibrium in the reduction of ketones, 1,4-butanediol acts essentially irreversibly owing to the formation of butyrolactone, which acts as a thermodynamic sink. It is therefore not necessary to use 1,4-butanediol in great excess in order to achieve reduction reactions. In addition, allylic alcohols are reduced to saturated alcohols through an isomerization/reduction sequence using a ruthenium catalyst with 1,4-butanediol as the reducing agent. Imines and alkenes are also reduced under similar conditions. [source] Efficient and Chirally Specific Synthesis of Phenanthro-Indolizidine Alkaloids by Parham-Type CycloacylationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2010Ziwen Wang Abstract A concise, efficient and modular route involving Parham-type cycloacylation as the key step has been used to synthesize six enantiopure phenanthro-indolizidine alkaloids 1a,c. The preparation of enantiomerically pure tylophora alkaloids and their seco analogues on a large-scale is now feasible. The alcohol intermediates 8a,c, which are difficult to prepare by other synthetic methodologies, have been synthesized by a metallation,cyclization,reduction sequence in excellent yields. [source] Biocatalytic Racemization of (Hetero)Aryl-aliphatic ,-Hydroxycarboxylic Acids by Lactobacillus spp.EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2006Proceeds via an Oxidation, Reduction Sequence Abstract The biocatalytic racemization of a range of (hetero)aryl- and (di)aryl-aliphatic ,-hydroxycarboxylic acids has been achieved by using whole resting cells of Lactobacillus spp. The essentially mild (physiological) reaction conditions ensure the suppression of undesired side reactions, such as elimination, decomposition or condensation. Cofactor/inhibitor studies using a cell-free extract of Lactobacillus paracasei DSM 20207 reveal that the addition of redox cofactors (NAD+/NADH) leads to a distinct increase in the racemization rate, while strong inhibition is observed in the presence of Thio-NAD+, which suggests that the racemization proceeds by an oxidation,reduction sequence rather than involvement of a "racemase" enzyme. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Left ventricular mechanical dyssynchrony is load independent at rest and during endotoxaemia in a porcine modelACTA PHYSIOLOGICA, Issue 4 2009R. A'roch Abstract Aim:, In diseased or injured states, the left ventricle displays higher degrees of mechanical dyssynchrony. We aimed at assessing mechanical dyssynchrony ranges in health related to variation in load as well as during acute endotoxin-induced ventricular injury. Methods:, In 16 juvenile anaesthetized pigs, a five-segment conductance catheter was placed in the left ventricle as well as a balloon-tipped catheter in the inferior vena cava. Mechanical dyssynchrony during systole, including dyssynchrony time in per cent during systole and internal flow fraction during systole, were measured at rest and during controlled pre-load reduction sequences, as well as during 3 h of endotoxin infusion (0.25 ,g kg,1 h,1). Results:, Systolic dyssynchrony and internal flow fraction did not change during the course of acute beat-to-beat pre-load alteration. Endotoxin-produced acute pulmonary hypertension by left ventricular dyssynchrony measures was not changed during the early peak of pulmonary hypertension. Endotoxin ventricular injury led to progressive increases in systolic mechanical segmental dyssynchrony (7.9 ± 1.2,13.0 ± 1.3%) and ventricular systolic internal flow fraction (7.1 ± 2.4,16.6 ± 2.8%), respectively for baseline and then at hour 3. There was no localization of dyssynchrony changes to segment or region in the ventricular long axis during endotoxin infusion. Conclusion:, These results suggest that systolic mechanical dyssynchrony measures may be load independent in health and during acute global ventricular injury by endotoxin. More study is needed to validate ranges in health and disease for parameters of mechanical dyssynchrony. [source] | ||||||||||