Studies of specifically fluorinated carbohydrates. Part II. Nuclear magnetic resonance studies of pentopyranosyl fluoride derivatives

Abstract

Detailed studies, by 1 H and 19 F nuclear magnetic resonance spectroscopy, of a series of fully esterified pentopyranosyl fluorides, show that all such derivatives favor that conformer in which the fluorine substituent is axially oriented. This conclusion is supported by separate considerations of the vicinal and geminal 19 F– 1 H and 1 H– 1 H coupling constants, of the long-range ( 4 J) 1 H– 1 H and 19 F– 1 H coupling constants and of the 19 F chemical shifts. The limitations of the above conformational model are discussed.