Diels-Alder Reactivity of Allenylboronic Acid Pinacol Ester and Related Dienophiles: Mechanistic Studies and Distortion/Interaction-Activation Strain Model Analysis.

A DFT study of the Diels-Alder reactions of vinylboronic acid pinacol ester, allenylboronic acid pinacol ester, methyl acrylate, and methyl 2,3-butadienoate with cyclopentadiene has been performed. Competitive mechanisms for the reactions of the carboxylic esters have been fully investigated, and similar results to those previously found for the organoboron compounds were obtained. Moreover, reactivity and selectivity patterns were correctly reproduced.

Allenylboronic Acid Pinacol Ester: A Selective Partner for [4 + 2] Cycloadditions.

We have studied the reaction of allenylboronic acid pinacol ester with cyclopentadiene with experimental and computational methods. The reaction occurred efficiently with complete Diels-Alder periselectivity and regioselectivity at the proximal double bond. The concerted mechanism for the observed transformation was computed to be favored over competitive addition to the distal double bond, [3,3]-sigmatropic rearrangements, and stepwise radical mechanism.

An NMR-Based Biosensor to Measure Stereospecific Methionine Sulfoxide Reductase Activities in Vitro and in Vivo*.

Oxidation of protein methionines to methionine-sulfoxides (MetOx) is associated with several age-related diseases. In healthy cells, MetOx is reduced to methionine by two families of conserved methionine sulfoxide reductase enzymes, MSRA and MSRB that specifically target the S- or R-diastereoisomers of methionine-sulfoxides, respectively. To directly interrogate MSRA and MSRB functions in cellular settings, we developed an NMR-based biosensor that we call CarMetOx to simultaneously measure both enzyme activities in single reaction setups.