Synthesis and properties of sulfated alkyl glycosides

Alkyl glycosides were sulfated with sulfur trioxide-pyridine. Dodecyl alpha- and beta-D-glucopyranoside gave the corresponding 6-sulfates in 75 and 51% yields, respectively. Separation from polysulfated compounds was carried out by reversed-phase HPLC. Tetradecyl beta-maltopyranoside (16) gave a 88: 12 mixture of 6'- and 6-sulfates. The sulfated compounds were characterized by 1H-, 13C-, and 2-dimensional NMR spectroscopy. Surfactant and thermotropic liquid-crystalline properties of the sugar derivatives were examined. All of the glycosides show smectic phases (SA), and the clearing points rise by introduction of sulfate groups. Even glycosides having no unprotected hydroxy groups may show SA-phases when bearing sulfate groups. The mesomorphic properties cannot be explained by formation of distinct aggregates, but rather must be interpreted by an effective intramolecular contrast.