The donor–acceptor biphenyl platform: A versatile chromophore for the engineering of highly efficient two-photon sensitive photoremovable protecting groups

Different photoremovable protecting groups in the o -nitrobenzyl, phenacyl, and 2-( o -nitrophenyl)propyl series with a donor–acceptor biphenyl backbone, known to display excellent two-photon absorption cross-sections, were investigated in order to develop efficient two-photon sensitive photoremovable protecting groups. The 2-( o -nitrophenyl)propyl series was a more versatile platform to increase the two-photon sensitivity of photoremovable protecting groups, leading to the p -alkoxy and p -bisalkylamino-4-nitro-[1,1′-biphenyl]-3-yl)propyl derivatives: PENB and EANBP respectively. Those two photoremovable protecting groups are to date the best caging groups for two-photon excitation at 800 and 740 nm respectively, offering attracting perspectives in chemical biology.