Photoinduced Bioorthogonal 1,3-Dipolar Poly-cycloaddition Promoted by Oxyanionic Substrates for Spatiotemporal Operation of Molecular Glues

Abstract

© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. PGluePZ, a pyrazoline (PZ)-based fluorescent adhesive which can be generated spatiotemporally in living systems, was developed. Since PGluePZ carries many guanidinium ion (Gu+) pendants, it strongly adheres to various oxyanionic substrates through a multivalent salt-bridge interaction. PGluePZ is given by bioorthogonal photopolymerization of a Gu+-appended monomer (GlueTZ), bearing tetrazole (TZ) and olefinic termini. Upon exposure to UV light, GlueTZ transforms into a nitrileimine (NI) intermediate (GlueNI), which is eligible for 1,3-dipolar polycycloaddition. However, GlueNI in aqueous media can concomitantly be deactivated into GlueWA by the addition of water, and the polymerization hardly occurs unless GlueNI is concentrated. We found that, even under high dilution, GlueNI is concentrated on oxyanionic substrates to a sufficient level for the polymerization, so that their surfaces can be point-specifically functionalized with PGluePZ by the use of a focused beam of UV light.