Development of New Pyrrolocoumarin Derivatives with Satisfactory Fluorescent Properties and Notably Large Stokes Shifts

Abstract Small, organic, fluorescent molecules with large Stokes shifts and long emission wavelengths are ideal dyes for various modern fluorescent imaging technologies such as FRET. In this study, we designed and synthesized a number of new fluorescent molecules on the basic structures of two pyrrolocoumarin skeletons where Fischer's indole synthesis and the Suzuki coupling successfully served as the efficient molecular editing protocols. The examination of the fluorescent properties and further structural optimization of these compounds afforded three new pyrrolocoumarin dyes with notably large Stokes shifts and satisfactory fluorescent properties. Among these, 30 showed a large Stokes shift (113 nm) and intense fluorescence (φ = 0.55, λem = 523 nm), and thus showed great potential in biological imaging studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)