Electrochemical synthesis and X-ray crystal structures of beta-D-2-phenylselenyl-1,3,4,6-tetra-O-acetylglucopyranose and alpha-D-2-phenylselenyl-1,3,4,6-tetra-O-acetylmannopyranose

摘要

Electrochemical acetoxyphenylselenation of 3,4-dihydro-2H-pyran and D-3,4,6-tri-O-acetylglucal was studied.The constant current electrolysis (50 mA)of dihydropyran and diphenyl diselenide in an acetic acid solution of tetamethylamonium chloride was performed at room temperautre in an undivided cell using a graphite anode and an aluminum cathode and yielded trans-DL-2-acetoxy-3-phenylselenyltetrahydropyran (27%),in agreement with markovnikov's rule.The analysis of the ~1H NMR spectral data showed tha thte acetoxy and phenylselenyl groups adopt axial positions inthe most stable conformation of this compound due to the anomeric effect.Under the same conditions D-3,4,6-tri-O-acetylglucal afforded D-2-phenylselenyl-1,3,4,6-tetra-O-acetylglucopyranose and D-2-phenylselenyl-1,3,4,6-tetra-O-acetylmannopyranose,which were separated by column chromatography and isolated in 87% overall yield (isomer ratio 60:40).The structures of these compounds were established by spectral data.single crystal X-ray structure determinations of the diasteromers are reported.