18268-81-0Relevant academic research and scientific papers
Catechol oxidase activity of Di-Cu2+-substituted aminopeptidase from Streptomyces griseus
Da Silva, Giordano F. Z.,Ming, Li-June
, p. 16380 - 16381 (2005)
Streptomyces griseus aminopeptidase exhibits activities toward the hydrolyses of peptides and bis(p-nitrophenyl)phosphate (40 billion fold) and catechol oxidation reported herein with catalytic efficiency (kcat/Km) only about 10 times smaller than that of gypsywort catechol oxidase. The multifunctionality of this enzyme suggests that it is a unique system for further exploration of protein structure and function and a template for design of enzymes of diverse activities. Copyright
Mechanism for Semiquinone Formation in the Oxygen Negative Chemical Ionization Mass Spectrometry of 2,3,7,8-Tetrachlorodibenzo-p-dioxin
Mitchum, Ronald K.,Korfmacher, Walter A.,Althaus, James R.
, p. 63 - 66 (1984)
The high toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) has led to the development of selective and highly sensitive quantitative methods for mass spectral analysis.Analytical selectivity has been demonstrated for the oxygen negative chemical ionization (ONCI) reaction of TCDD in an oxygen-rich plasma.While the reaction product (4,5-dichloro-1,2-benzoquinone anion) of 2,3,7,8-TCDD and oxygen is well known, the mechanism of its formation has not been studied thoroughly.In this report the results of a study involving the reaction of (18)O2 with 2,3,7,8-TCDD under high pressure and low pressure ONCI conditions are reported.A mechanism is proposed which is compatible with the observation that one (18)O atom is incorporated into the product anion.
A surprising mechanistic "switch" in Lewis acid activation: A bifunctional, asymmetric approach to α-hydroxy acid derivatives
Abraham, Ciby J.,Paull, Daniel H.,Bekele, Tefsit,Scerba, Michael T.,Dudding, Travis,Lectka, Thomas
supporting information; experimental part, p. 17085 - 17094 (2009/04/13)
We report a detailed synthetic and mechanistic study of an unusual bifunctional, sequential hetero-Diels-Alder/ring-opening reaction in which chiral, metal complexed ketene enolates react with o-quinones to afford highly enantioenriched, α-hydroxylated carbonyl derivatives in excellent yield. A number of Lewis acids were screened in tandem with cinchona alkaloid derivatives; surprisingly, trans-(Ph3P)2PdCl2 was found to afford the most dramatic increase in yield and rate of reaction. A series of Lewis acid binding motifs were explored through molecular modeling, as well as IR, UV, and NMR spectroscopy. Our observations document a fundamental mechanistic "switch", namely the formation of a tandem Lewis base/Lewis acid activated metal enolate in preference to a metal-coordinated quinone species (as observed in other reactions of o-quinone derivatives). This new method was applied to the syntheses of several pharmaceutical targets, each of which was obtained in high yield and enantioselectivity.
