Synthesis, characterization and photophysical studies of the flavopeptide conjugates as model for the covalently linked flavoenzymes

Here, we have demonstrated an easy and efficient synthetic route for the synthesis of the flavo-peptide conjugates as model for the naturally occurring covalently linked flavoenzymes. A judicially functionalized flavin analogue was used for the coupling reaction with the pre-synthesized peptidic motifs using solution-phase chemistry. Representative examples using mono-, di- and tripeptides were reported to couple with the C7-position of the flavin moiety to showcase the generic nature of the synthetic strategy. Further photophysical investigation including quantum yield measurements, concentration-dependent studies and fluorescence quenching experiments reveal the intramolecular nature of the charge transport process in cases where tyrosine is present, similar to that found in the natural counterpart.

Graphical abstract

This manuscript discusses a simple/efficient approach for the synthesis of flavopeptide conjugates as a true model for covalently-liked-flavoenzymes. Coupling reaction between the suitably functionalized flavin moiety and the pre-synthesized peptide entities was envisaged and undertaken to prove the generality of the approach. Further photophysical investigation including quantum yield measurements, concentration-dependent studies and fluorescence quenching experiments reveal the intramolecular nature of the charge transport process in cases where tyrosine is present, similar to that found in the natural counterpart. Such a synthetic flavopeptide model may provide a further investigation to provide an insight into the corresponding biological phenomenon.