Protein Modification of Lysine with 2-(2-Styrylcyclopropyl)ethanal.

A new lysine-reactive cyclopropropyl aldehyde for the covalent modification of proteins was developed. The reagent exploits a divinylcyclopropane-cycloheptadiene rearrangement to render the initial condensation irreversible. A labeling study on eGFP demonstrated excellent chemoselectivity for the modification of amine-nucleophiles with the possibility of subsequent modifications.

Dienamine-Induced Divinylcyclopropane-Cycloheptadiene Rearrangements.

Sigmatropic rearrangements constitute an important group of pericyclic reactions. In contrast to cycloaddition reactions, examples of catalytic variants of electrocyclic reactions and sigmatropic rearrangements are still scarce in the chemical literature. Herein, we report the first organocatalytic Cope rearrangement of in situ-generated divinylcyclopropanes. The reactive motif was generated by condensation of 4-(2-vinylcyclopropyl)but-2-enal derivatives with a secondary amine catalyst to form a transient dienamine. The cycloheptadiene products could be obtained in high yield and excellent diastereoselectivity. Importantly, the reaction was demonstrated to be stereospecific, proceeding under mild conditions, while exhibiting broad functional group tolerance.