Zeolite-catalyzed Helferich-type glycosylation of long-chain alcohols. Synthesis of acetylated alkyl 1,2-trans glycopyranosides and alkyl 1,2-cis C2-hydroxy-glycopyranosides.
Zeolite-catalyzed glycosylation of long-chain alcohols, using the inexpensive and readily available peracetylated beta-D-gluco- and galactopyranoses as glycosyl donors under solvent free conditions, has been explored for the first time. Among the various forms (H-, Na-, Fe- and Zn) of beta zeolite examined as catalysts in the reaction of 1,2,3,4,6-penta-O-acetyl-beta-D-galactopyranose with cetyl alcohol, Fe-beta zeolite gave the maximum yield of 63% of cetyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranoside and cetyl 3,4,6-tri-O-acetyl-alpha-D-galactopyranoside. Fe-beta Zeolite-catalyzed glycosylation was found to be general affording the title compounds in each case in a moderate yield, but with a good stereoselectivity. The yield of synthetically valuable acetylated long-chain alkyl 1,2-cis C2-hydroxy-glycopyranosides obtained in the present single-step procedure is considerably higher than that of the previously reported multi-step method employing the Stork silicon tether approach.
Aich
Udayanath
U
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India.
Loganathan
Duraikkannu
D
D002384:Catalysis; D005233:Fatty Alcohols / Q000138:chemical synthesis / Q000737:chemistry*; D005697:Galactosides / Q000138:chemical synthesis / Q000737:chemistry*; D006017:Glycolipids / Q000138:chemical synthesis* / Q000737:chemistry; D006031:Glycosylation; D017641:Zeolites / Q000138:chemical synthesis / Q000737:chemistry*
D005233:Fatty Alcohols; D005697:Galactosides; D006017:Glycolipids; C519394:cetyl 2,3,4,6-tetra-O-acetylgalactopyranoside; C519393:cetyl 3,4,6-tri-O-acetylgalactopyranoside; D017641:Zeolites; C020450:1,2,3,4,6-penta-O-acetylgalactopyranose; C005031:cetyl alcohol