RESUMO
The catalytic use of a sodium amide has been exploited for formal allylic C(sp3)-H bond activation of alkenes under mild conditions. Subsequent C-C bond formations with imines have proceeded in high yields with complete regioselectivity and excellent geometric selectivity. Aromatic cyano, chloro, and bromo functionalities are tolerated by the transition metal-free catalyst. Complex amines bearing a CâC double bond and distinct heteroaromatic units have been prepared in a single step. The critical importance of sodium versus other s-, p-, d-, and f-block metals as well as metal-free systems has been revealed. In addition, two catalytically active sodium-based intermediates were detected by NMR and HRMS analyses.
RESUMO
Described in this work is a novel method for photochemically manipulating peptides and proteins via the installation of cysteine-selective photoactive tags. Thiomaleimides, generated simply by the addition of bromomaleimides to reduced disulfide bonds, undergo [2 + 2] photocycloadditions to reconnect the crosslink between the two cysteine residues. This methodology is demonstrated to enable photoactivation of a peptide by macrocyclisation, and reconnection of the heavy and light chains in an antibody fragment to form thiol stable conjugates. Finally we report on an intriguing thiomaleimide mediated photochemical decarboxylation of C-terminal cysteines, discovered during this study.
Assuntos
Cisteína/química , Dissulfetos/química , Maleimidas/química , Ciclização , Descarboxilação , Maleimidas/síntese química , Estrutura Molecular , Processos FotoquímicosRESUMO
Tuning the properties of maleimide reagents holds significant promise in expanding the toolbox of available methods for bioconjugation. Herein we describe aryloxymaleimides which represent 'next generation maleimides' of attenuated reactivity, and demonstrate their ability to enable new methods for protein modification at disulfide bonds.
