organocatalyst trityl chloride (ph3ccl), by in situ formation of trityl carbocation with inherent instability, efficiently catalyzes the condensation of dimedone (5,5-dimethyl-1,3-cyclohexanedione) (2 equiv.) with arylaldehydes (1 equiv.) under solvent-free conditions to afford 9-aryl-1,8-dioxo-octahydroxanthenes in high to excellent yields and in relatively short reaction times. formation of t...

Deamination of native rat tail collagen followed by treatment with 1,2-cyclohexanedione removes the positive charge from the side chains of the lysine and hydroxylysine residues and blocks approximately 7 0 % of the positively charged side chains of the arginine residues. When such specimens are examined in the electron microscope after negative staining with 2 % potassium phosphotungstate at p...

We report results on dispersion relations and instabilities of traveling waves in excitable systems. Experiments employ solutions of the 1,4-cyclohexanedione Belousov–Zhabotinsky reaction confined to thin capillary tubeswhich create a pseudo-one-dimensional system. Theoretical analyses focus on a threevariable reaction–diffusion model that is known to reproduce qualitatively many of the experim...

The immunoglobulin G binding site in the globular regions of human complement subcomponent C1q has been investigated by chemical modification of histidine residues with diethylpyrocarbonate and arginine residues with phenylglyoxal and cyclohexane-1,2-dione (CHD). Only the modification of arginine residues with CHD fulfills the requirements of a specific modification without unwanted side reacti...

Metabolic heterogeneity in low density lipoprotein (LDL) may be detected by examination of the daily urinary excretion rate of radioactivity after injection of trace-labeled lipoprotein. Two distinct pools are observed within LDL. The first (pool A) is cleared rapidly from the plasma, whereas the second (pool B) is catabolized more slowly. In the present study we examined LDL metabolism in seve...

Cyclic alcohols Cyclohexane-1.2-dione hydrolase Thiamine diphosphate Flavoenzyme Alicyclic alcohols are naturally occurring compounds wh ich can be degraded by microorgan isms via cleavage of the ring CC bond. DenitrifyingAzoarcus sp. strain 22Lin grows on cyclohexane-l .2-diol which serves as electron donor and carbon source. The diol is converted to cyclohexane-l.2-dione followed by hydrolysi...

Human serum albumin (HSA) has been chemically modified with 1,2-cyclohexanedione and N-acetylimidazole under nondenaturing conditions. Derivatives, in which 10 arginine residues (1,2-dihydroxycyclohex-1,2-ylene (DHCH)-HSA), 56 to 57 lysine and 5 tyrosine residues (acetyl-HSA), or 56 to 57 lysine residues alone (O-deacetyl-HSA) are modified, have been isolated. Their conformation has been tested...

Incubation of homogeneous preparations of L-threonine dehydrogenase from Escherichia coli with 2,3-butanedione, 2,3-pentanedione, phenylglyoxal, or 1,2-cyclohexanedione causes a time- and concentration-dependent loss of enzymatic activity; plots of log percent activity remaining versus time are linear to greater than 90% inactivation, indicative of pseudo-first order inactivation kinetics. The ...

ABSTRACT Polyvinylpolypyrrolidone supported chlorosulfonic acid ([PVPP-SO3H]+Cl-) was synthesized and evaluated as a recoverable catalyst for the one-pot synthesis of hexahydroquinolines by reaction of arylaldehydes, dimedone (5,5-dimethylcyclohexane-1,3-dione) or 1,3-cyclohexanedione, ethylacetoacetate and ammonium acetate in high to excellent yield in ethanol at 70 °C. The [PVPP-SO3H]+Cl- cat...

A simple and efficient method for the synthesis of quinolines and polycyclic quinolines using Li+ modified nanoporous Na+-montmorillonite is described. This new nanocatalyst proceeds via Friedlander annulation under solvent-free conditions. It describes our observations about a trend of catalytic activity of Lithium cation in nanoporous Na+-montmorillonite. In this study, several types of 1,3-d...