CATION-EXCHANGE RESIN-CATALYZED ADDITION OF METHANOL TO BENZOYLATED 1,5-ANHYDRO-2-DEOXY-D-HEX-1-ENITOLS

Article abstract of DOI:10.1016/S0008-6215(00)81000-9

1,5-Anhydro-3,4,5-tri-O-benzoyl-2-deoxy-D-arabino-hex-1-enitol (1) was boiled under reflux with methanol and AG 50W-X8 cation-exchange resin.A two-product mixture of glycosides (2 and 3) was obtained in 38percent yield, together with 19percent of unreacted material. 1,5-Anhydro-3,6-di-O-benzoyl-2-deoxy-D-arabino-hex-1-enitol (7) was prepared from 1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol by selective benzoylation, from wich the corresponding 4-methansulphonate 8 was obtained.Treatment of 8 with sodium benzoate in hexamethylphosphoric triamide for 72 h at 100 deg C afforded 1,5-anhydro-3,4,6-tri-O-benzoyl-2-deoxy-D-xylo-hex-1-enitol (9) in 52percent yield.An unknow byproduct (B), tentitatively shown to be a tri-O-benzoyl-D-hex-2-enopyranose analog, was also isolated in 14percent yield.The 270-MHz n.m.r. spectrum of B was analyzed in terms of its J_1,3, J_2,4 and J_4,5 coupling constant in relation to the various configurational and conformational possibilities for hex-2-enopyranose, and was identified as 1,4,6-tri-O-benzoyl-2,3-dideoxy-α-D-threo-hex-2-enopyranose having the ^oH₅ conformation.The analysis presented should also be applicable to pent-2-enopyranose systems.When 9 was treated with methanol in the presence of AG 50W-X8 cation-exchange resin, a mixture of glycosides 4 and 5 was obtained in 47percent yield.The low yields were attributed to methanolysis of the benzoyl groups during the reaction.