Reductive Ring‐Opening Reaction of 1,2‐O‐Benzylidene and 1,2‐O‐p‐Methoxybenzylidene‐α‐D‐glucopyranose Using Diisobutyl Aluminum Hydride
摘要:
Regioselectivity in the reductive ring-opening reaction of 3,4,6-tri-O-benzyl-1,2-O-benzylidene and 3,4,6-tri-O-benzyl-1,2-O-p-methoxybenzylidene-alpha-D-glucopyranose using diisobutyl aluminum hydride (DIBAH) was examined. The ratio of the 1-O- and 2-O-p-methoxybenzyl ethers, which were generated from endo-type 1,2-O-p-methoxybenzylidene, was variable by the change of solvent.
An improved and practical synthesis of 1,2-O-benzylidene and 1,2-O-p-methoxybenzylidene hexopyranoses as useful synthons in carbohydrate chemistry is described. The reaction of 2-benzoyloxyglycosyl bromide with sodium borohydride using excess amount of potassium iodide proceeded smoothly to give the corresponding 1,2-O-benzylidene derivative in good yields.