Thermodynamically Controlled Regioselective Glycosylation of Fully Unprotected Sugars through Bis(boronate) Intermediates

Fully unprotected D‐glucose, D‐mannose, and D‐fructose were regioselectively glycosylated with several phenylthioglycosides to afford glycosyl‐β(1→6)‐α/β‐D‐glucopyranose, glycosyl‐β(1→1)‐α‐D‐mannofuranoside, and glycosyl‐β(1→1)‐β‐D‐fructopyranose in good yields. The regioselectivity might have arisen from a thermodynamically controlled bis(phenylboronate) intermediate, which leaves only one free hydroxy group to be glycosylated in complete regioselectivity.