名称:
DDQ-Mediated Oxidation of 4,6-O-Methoxybenzylidene-Protected Saccharides in the Presence of Various Nucleophiles: Formation of 4-OH, 6-Cl, and 6-Br Derivatives
摘要:
Treatment of 4,6-O-p-methoxybenzylidene-protected pyranosidic mono- and disaccharides with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), in the presence of a few equivalents of water, gave the corresponding 6- and 4-O-p-methoxybenzoates with unprotected hydroxyl groups in the 4- and 6-position in the ratio similar to 4:1 and in 85-98% yield. Dry conditions in the presence of halide salts gave the 6-deoxychloro and -bromo 4-O-p-methoxybenzoates exclusively, in >90% yield.