Regioselective synthesis of long-chain ethers and their sulfates derived from methyl beta-D-galactopyranoside and derivatives via dibutylstannylene acetal intermediates.
A number of different conditions were investigated for the alkylation of the dibutylstannylene acetals of methyl beta-d-galactopyranoside with long-chain primary alkyl bromides, decyl, dodecyl, and tetradecyl bromide. The best yields of the major products, the 3-O-alkyl ethers, were obtained by reaction of the alkyl bromide with the monodibutylstannylene acetal in DMF in the presence of cesium fluoride for extended periods of time at moderate temperatures (65 degrees C). These products were always accompanied by minor amounts of the 3,6-di-O-alkyl derivative. Performing the reaction with excess alkyl halide on the bis(dibutylstannylene) acetal resulted in more of the 3,6-di-O-alkyl derivative, particularly for the shorter alkyl bromides, but this product was never predominant. Sulfation of the dibutylstannylene acetal of methyl 3-O-tetradecyl-beta-D-galactopyranoside resulted in the 6-sulfate in 96% yield.
Gonçalves
Alan G
AG
Department of Chemistry, Dalhousie University, Halifax, NS, Canada B3H 4J3.
Noseda
Miguel D
MD
Duarte
M E R
ME
Grindley
T Bruce
TB
D004987:Ethers / Q000138:chemical synthesis*; D008756:Methylgalactosides / Q000138:chemical synthesis / Q000737:chemistry*; D013463:Sulfuric Acid Esters / Q000138:chemical synthesis*
D004987:Ethers; D008756:Methylgalactosides; D013463:Sulfuric Acid Esters