Département de Chimie, Université de Montréal, P.O. Box 6128, Station Downtown, Montréal, Québec, Canada H3C 3J7.
Published: April 2003
AI Article Synopsis
Article Abstract
A new class of orthoacylimine-derived chiral auxiliaries has been synthesized and tested in the nucleophilic addition of organolithium reagents to imines. The precursors can be prepared by an aza-Wittig reaction between the corresponding orthoacyl azide and a variety of aldehydes in the presence of trialkylphosphines. The nucleophilic addition of organolithium reagents led to the addition products in good yields and with good to excellent diastereoselectivities (from 85:15 to 99:1). The chiral, nonracemic secondary amines could be readily obtained under mild hydrolytic condition. Furthermore, the chiral auxiliary can be recovered in quantitative yield and reconverted to the starting orthoacyl azide precursor. This method was applied to the synthesis of (S)-t-leucine.
Biodiesel offers an alternative to fossil fuels, primarily because it is derived from renewable sources, with the potential to mitigate issues such as pollutant and greenhouse gas emissions, resource scarcity, and the market instability of petroleum derivatives. However, lower durability and stability pose challenges. To address this, researchers worldwide are exploring technologies that employ specific molecules to slow down biodiesel's oxidation process, thereby preserving its key physicochemical properties.
Enzyme promiscuity is the ability of an enzyme to catalyze an unexpected side reaction in addition to its main reaction. Here, we describe a biocatalytic process to produce non-hydrolyzable NAD+ analogs based on the ADP-ribosyltransferase (ART) activity of pertussis toxin PtxS1 subunit. First, in identical manner to normal catalysis, PtxS1 activates NAD+ to form the reactive oxocarbenium cation.
The Division of Structural Biology, The Nuffield Department of Medicine, University of Oxford, UK; The Rosalind Franklin Institute, Harwell Campus, Didcot, OX11 0QS, UK. Electronic address:
Multifunctionality, processivity, and thermostability are critical for the cost-effective enzymatic saccharification of non-food plant biomass polymers such as β-glucans, celluloses, and xylans to generate biofuels and other valuable products. We present molecular insights into a processive multifunctional endo-1,3-1,4-β-d-glucanase (Tt_End5A) from the hyperthermophilic bacterium Thermogutta terrifontis. Tt_End5A demonstrated activities against a broad spectrum of β-polysaccharides, including barley glucan, lichenan, carboxymethyl cellulose, regenerated amorphous cellulose (RAC), Avicel, xylan, laminarin, mannan, curdlan, xanthan, and various chromogenic substrates at pH 7 and temperatures ranging from 70 to 80°C.
Nucleophilic addition to α,β-unsaturated carbonyl compounds normally occurs at the carbonyl carbon or β-carbon. The direct α-nucleophilic addition at the α-carbon can hardly be achieved due to electronic mismatch. In this work, we report the nucleophilic addition of β-fluoroalkyl α-carbonyl carbocations that are prepared via -induced redox-neutral photocatalysis.
We disclose a broad platform for copper-catalyzed atom transfer radical addition (ATRA) of electron-deficient olefins. Catalytic Cu(dtbbpy)(OTf) enables radical addition of electron-deficient alkyl halides to acrylates, acrylamides, and vinyl sulfones in fair to excellent yields. The resultant ATRA products can be used in a variety of telescoped reactions, including substitution with basic amine nucleophiles to afford α-amino esters.
