Abstract
Fluorescence is a powerful and versatile spectroscopic method for studying molecular and biological interactions or cellular processes. In this field, the development of small functionalized red-emitting dyes with a large Stokes shift for convenient biomolecules labeling is a hot topic, either to minimize the perturbations of the native biochemical processes, to avoid the reabsorption of light and to improve sensitivity.[1] For this purpose, phospholes which have the characteristics of a dienic system bridged with a tetrahedral phosphorus atom, are attractive π-conjugated heterocycles, mainly developed for optoelectronic devices.[2] However, the use of fluorescent phospholes in bioimaging is rare despite their relatively low molecular weight, lack of known toxicity and high photochemical stability in regard to other classes of fluorophores.[3,4] As the chemistry and the functionalization of phospholes require of strategies often associated with severe conditions, this constitutes an unquestionable limit for their design.[5] Therefore, we investigated the grafting of phosphole-based fluorophores to the pendant group of peptides through the P-center by formation of P-N and P-S bonds. Herein, we report the synthesis of a new class of fluorescent phospholes bearing a leaving group at the P-center and their use in coupling to peptides, under mild conditions, for Solution Phase Synthesis (SPS) and Solid Phase Peptide Synthesis (SPPS). This new method was illustrated by the labeling of the Growth Hormone Secretagogue Receptor type 1a (GHS-R1a) ligands. Finally, binding assay of GHS-R1a based on Fluorescence Resonance Energy Transfer (FRET) with labeled ligands has been demonstrated.References:[1] H. Singh et al. Chem. Rev. 2019, 119, 11718-11760.[2] M. P. Duffy et al. Chem. Soc. Rev. 2016, 5296-5310.[3] C. Wang et al. J. Am. Chem. Soc. 2017, 139, 10374−10381.[4] Y. Sugihara et al. Chem. Sci., 2021, 12, 6333-6341.[5] M. Arribat et al. J. Am. Chem. Soc. 2018, 140, 1028-1034.