Palladium (II) coordination complexes catalyze the reaction of alcohols with ketones to yield ethers. During the catalytic cycle, the alcohol adds selectively to the β-carbon (anti-Markovnikov). In this work, mechanism and kinetics for the reaction of methanol with methyl vinyl ketone (MVK), being catalyzed by Pd, has been theoretically investigated in detail. Using quantum mechanical approach,...

Cholest-8(14)-enol is the major radioactive component of the 4-di-demethyl sterol fraction biosynthesized from 4,4-dimethyl[2-(3)H(2)]cholest-8(14)-enol by rat liver microsomal fractions, and therefore the first steps in the biosynthesis of cholesterol from the latter compound probably involve removal of the 4-methyl groups. 4,4-Dimethylcholesta-8,14-dienol therefore is not an intermediate in t...

NEIL1 (Nei-like 1) is a DNA repair glycosylase guarding the mammalian genome against oxidized DNA bases. As the first enzymes in the base-excision repair pathway, glycosylases must recognize the cognate substrates and catalyze their excision. Here we present crystal structures of human NEIL1 bound to a range of duplex DNA. Together with computational and biochemical analyses, our results sugges...

Equilibrium constants for keto-enol tautomerisation and migration of hydrogen from carbon to nitrogen to form enamine or zwitterion tautomers have been measured for 2-, 3and 4phenacylpyridines (PyCH,COPh) in aqueous solution at 25 "C. Relative tautomeric stabilities fall in the order ketoimine > enamine > enol and (for the 3-isomer) enol > zwitterion. Values of pKT, (-log KT) where KT = [enamin...

The enol of a-cyano-a-phenylacetic acid was observed as a short-lived transient species formed upon flash photolytic generation of phenylcyanoketene by a photo-Wolff reaction of a-cyano-a-diazoacetophenone followed by hydration of the ketene. Rates of ketonization of the enol were measured in dilute hydrochloric acid solutions and acetic acid, biphosphate ion, tris(hydroxymethyl)methylamine, an...

Palladium (II) coordination complexes catalyze the reaction of alcohols with ketones to yield ethers. During the catalytic cycle, the alcohol adds selectively to the β-carbon (anti-Markovnikov). In this work, mechanism and kinetics for the reaction of methanol with methyl vinyl ketone (MVK), being catalyzed by Pd, has been theoretically investigated in detail. Using quantum mechanical approach,...

A robust method for preparing (E)and (Z)-stereodefined fully substituted enol tosylates is described. α-Substituted β-keto esters undergo (E)-selective enol tosylations using TsCl–Me2N(CH2)6NMe2 as the reagent (method A, 13 examples; 63–96%) and (Z)-selective enol tosylations using TsCl–TMEDA–LiCl as the reagent (method B, 13 examples; 62–99%). A plausible mechanism for the (E)and (Z)-enol tosy...

quirement that 13 be converted to an enol, which is also a methylenecyclobutane totally shuts down turnover. That 13 is not a better inhibitor reveals the subtlety of the recognition of this enzyme for its substrate. The isoleucine precursor cu,p-dihydroxy-p-methylvaleric acid differs from 13 only by the addition of two hydrogens. The activity of vinyl fluoride 15, possibly acting as a stable e...