Herein, the synthesis and photochemical study of (E)-2-cyano-3-(6-(dimethylamino)naphthalen-2-yl)-N-(β-D-glucopyranosyl)acrylamide, a β-D-glucopyranosyl analogue of the widely used molecular rotor julolidine. The new compound is a fluorescent inhibitor of rabbit muscle glycogen phosphorylase with properties of a molecular rotor. Fluorescence measurements in solutions of increasing viscosity determined that the fluorescence intensity increases with the viscosity of the medium, indicating that the new compound exhibits molecular rotor characteristics. Although the compound fluoresces negligibly in aqueous buffer solution, in the presence of increasing amounts of rabbit muscle glycogen phosphorylase, we observed an increase of fluorescence intensity, attributed to the formation of and inhibitor:enzyme complex. Invitro cellular studies were also undertaken, yielding promising preliminary results for the use of the new compound as a fluorescent probe.

A study of the first fluorescent potent inhibitor of glycogen phosphorylase showcases how emission is controlled by two independent rotations of two aromatic moieties.

Dysregulation of glycogen phosphorylase, an enzyme involved in glucose homeostasis, may lead to a number of pathological states such as type 2 diabetes and cancer, making it an important molecular target for the development of new forms of pharmaceutical intervention. Based on our previous work on the design and synthesis of 4-arylamino-1-(β-d-glucopyranosyl)pyrimidin-2-ones, which inhibit the activity of glycogen phosphorylase by binding at its catalytic site, we report herein a general synthesis of 2-substituted-5-(β-d-glucopyranosyl)pyrimidin-4-ones, a related class of metabolically stable, C-glucosyl-based, analogues. The synthetic development consists of a metallated heterocycle, produced from 5-bromo-2-methylthiouracil, in addition to protected d-gluconolactone, followed by organosilane reduction. The methylthio handle allowed derivatization through hydrolysis, ammonolysis and arylamine substitution, and the new compounds were found to be potent (μM) inhibitors of rabbit muscle glycogen phosphorylase. The results were interpreted with the help of density functional theory calculations and conformational analysis and were compared with previous findings.

Molecular rotors belong to a family of fluorescent compounds characterized as molecular switches, where a fluorescence on/off signal signifies a change in the molecule’s microenvironment. Herein, the successful synthesis and...