A Natural Alkaloid, β-Carboline, as a One- and Two-Photon Responsive Fluorescent Photoremovable Protecting Group: Sequential Release of the Same or Different Carboxylic Acids.

The β-carboline moiety, substituted at the C1 and C3 benzylic positions with a leaving group, has been demonstrated for the first time as a photoremovable protecting group for time-dependent sequential release of two (same or different) carboxylic acids upon one- and two-photon light irradiation. Density functional theory calculations suggest that the electronic environment of the β-carboline moiety at C1 and C3 positions plays a key role in the rate of photorelease.