Synthesis and evaluation of dual wavelength fluorescent benzo[b]thiophene boronic acid derivatives for sugar sensing.

Cell surface glycoproteins have been known to play very important roles in various physiologic and pathologic processes. Small molecule compounds capable of carbohydrate recognition can be very useful for the development of sensing, diagnostic, and therapeutic agents. Along this line, we are interested in developing water-soluble fluorescent boronic acid compounds for carbohydrate recognition. As such, a series of benzo[b]thiophene boronic acid derivatives have been synthesized and their fluorescent properties analyzed at physiologic pH. Benzo[b]thiophene derivatives were found to be a new type of fluorescent reporter compounds capable of dual fluorescent emission under physiologic pH conditions. Compounds 1, 3, 4, 5, and 6 showed unusual emission wavelength shifts upon binding of sugars. These boronic acids will be useful tools for building glycoprotein biosensors for biologic applications.