50624-94-7Relevant articles and documents
Identification and Reactivity of s- cis, s- cis-Dihydroxycarbene, a New [CH2O2] Intermediate
Quanz, Henrik,Bernhardt, Bastian,Erb, Frederik R.,Bartlett, Marcus A.,Allen, Wesley D.,Schreiner, Peter R.
, p. 19457 - 19461 (2020)
We report the first preparation of the s-cis,s-cis conformer of dihydroxycarbene (1cc) by means of pyrolysis of oxalic acid, isolation of the lower-energy s-trans,s-trans (1tt) and s-cis,s-trans (1ct) product conformers at cryogenic temperatures in a N2 matrix, and subsequent narrow-band near-infrared (NIR) laser excitation to give 1cc. Carbene 1cc converts quickly to 1ct via quantum-mechanical tunneling with an effective half-life of 22 min at 3 K. The potential energy surface features around 1 were pinpointed by convergent focal point analysis targeting the AE-CCSDT(Q)/CBS level of electronic structure theory. Computations of the tunneling kinetics confirm the time scale of the 1cc → 1ct rotamerization and suggest that direct 1cc → H2 + CO2 decomposition may also be a minor pathway. The intriguing latter possibility cannot be confirmed spectroscopically, but hints of it may be present in the measured kinetic profiles.
Cationic Chiral Pd-Catalyzed “Acetylenic” Diels–Alder Reaction: Computational Analysis of Reversal in Enantioselectivity
Honda, Kazuya,Ohkura, Shun,Hayashi, Yoshihiro,Kawauchi, Susumu,Mikami, Koichi
supporting information, p. 2842 - 2846 (2018/09/25)
The highly enantioselective Diels–Alder reaction of acetylenic dienophiles is shown to be effectively catalyzed by cationic chiral palladium complexes. Not only the degree but also the sense of enantioselectivity critically depends on the steric demand of ligands. Computational analyses indicate that the steric demand does not affect the endo/exo-selectivity but the enantioface selectivity of dienes.
O-alkyl hydroxamates as metaphors of enzyme-bound enolate intermediates in hydroxy acid dehydrogenases. Inhibitors of isopropylmalate dehydrogenase, isocitrate dehydrogenase, and tartrate dehydrogenase
Pirrung, Michael C.,Han, Hyunsoo,Chen, Jrlung
, p. 4527 - 4531 (2007/10/03)
The inhibition of Thermus thermophilus isopropylmalate dehydrogenase by O-methyl oxalohydroxamate was studied for comparison to earlier results of Schloss with the Salmonella enzyme. It is a fairly potent (1.2 μM), slow-binding, uncompetitive inhibitor against isopropylmalate and is far superior to an oxamide (25 mM Ki competitive) that is isosteric with the ketoisocaproate product of the enzyme. This improvement in inhibition was attributed to its increased NH acidity, which presumably is due to the inductive effect of the hydroxylamine oxygen. This principle was extended to the structurally homologous enzyme isocitrate dehydrogenase from E. coli, for which the compound O-(carboxymethyl) oxalohydroxamate is a 30 nM inhibitor, uncompetitive against isocitrate. The pH dependence of its inhibition supports the idea that it is bound to the enzyme in the anionic form. Another recently discovered homologous enzyme, tartrate dehydrogenase from Pseudomonas putida, was studied with oxalylhydroxamate. It has a relatively low affinity for the enzyme, though it is superior to tartrate. On the basis of these leads, squaric hydroxamates with increased acidity compared to squaric amides directed toward two of these enzymes were prepared, and they also show increased inhibitory potency, though not approaching the nanomolar levels of the oxalylhydroxamates.
