Convenient multigram scale glycosylations of scented alcohols employing phase-transfer reactions

Various conditions for glycosylation (Koenigs-Knorr, Helferich, trichloroacetimidate, Fischer-Raske, phase-transfer methods) of 3-ethoxy-4-hydroxybenzaidehyde (ethyl vanillin), 3-hydroxy-2-methyl-4-pyranone (maltol) and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (furaneol((R))) were evaluated, taking into account yields and ease of preparation (e.g., utilized donor, catalyst, conditions). The best results were achieved employing phase transfer catalysis in a two-phase solvent mixture. To increase water solubility for better applicability, the hitherto unknown maltosides of the corresponding alcohols were synthesized, again proving the value of phase-transfer conditions for glycosylation of phenols.