Water-Soluble Glucosyl Pyrene Photosensitizers: An Intramolecularly Synthesized 2- C-Glucoside and an O-Glucoside.

Prevalent photosensitizing agents for photodynamic therapy (PDT) suffer from their relatively large molecular weights causing photodermatosis. In this regard, low molecular weight pyrene could be an efficient photosensitizer except for its extreme hydrophobicity. To tackle the insolubility of pyrene, we synthesized 1-carboxypyren-2-yl C-glucoside 4 by a tethered C-glucosylation and 1-pyrenylmethyl O-glucoside 5 by a simple O-glucosylation. Compounds 4 and 5 showed modest water solubilities of 72 and 47 μg/mL, respectively. Whereas compound 4 partially underwent a cyclization reaction at pH 3 to give the corresponding δ-valerolactone 15b in 31% yield after 24 h, it is stable at pH 5-9 for at least a week. The 1O2-producing photosensitizabilities of 4 and 5 were sufficient to apply to PDT. Although compound 5 was uptaken by HeLa cells and showed a good PDT activity, compound 4 showed neither a sufficient cell uptake nor PDT effect. The binding modes of compounds 4 and 5 to concanavalin A were specific and unspecific, respectively. These results demonstrate that compounds 4 and 5 are within a pharmacologically acceptable range as oral drugs and could be a fluorescence imaging probe for α-glucose/mannose receptors and a photosensitizing agent for PDT, respectively.