Reactions of some 2- and 4-O-triflylglycopyranosides with MeLi, t-BuOK, and pyridine Original Research Article

As an extension of our previous work on secondary triflates of carbohydrates [El Nemr, A.; Tsuchiya, T. Tetrahedron Lett. 1995, 36, 7665–7668. El Nemr, A.; Tsuchiya, T.; Kobayashi, Y. Carbohydr. Res. 1996, 293, 31–59. El Nemr, A.; Tsuchiya, T. Carbohydr. Res. 1997, 301, 77–87. El Nemr, A.; Tsuchiya, T. Carbohydr. Res. 1997, 303, 267–281], the reaction modes of several methyl 2- and 4-O-triflyl-d-glycopyranosides with MeLi (strong base), t-BuOK (moderately strong base), and pyridine (weak base) have been studied. This paper describes the reactions of 3-O-benzyl-4,6-O-benzylidene-2-O-triflyl-d-gluco and -mannopyranosides with MeLi to give mainly the corresponding 2-C-methyl derivatives through α-elimination, with t-BuOK to give either the 2,3-unsaturated compounds through β-elimination or detriflyl 2-ols, and with hot pyridine to give the corresponding 2-pyridinium salts with inversion (except for the 2-O-triflyl-α-d-mannopyranoside (8)). 2,3,6-Tri-O-benzyl-4-O-triflyl-α-d-gluco and -mannopyranosides were also examined similarly.