The conformations of new CF3 and CF3-CHF containing amides derived from carbohydrates: NMR, crystallographic and DFT study.

A new convenient synthetic procedure for the preparation of tri- and tetrafluoropropanamides derived from sugars has been described. The conformations of fluorinated amides calculated for isolated molecules and those in the crystal state have been compared. In contrast to single α-fluorine substituted amides, which preferred the anti conformation around the F–C–C=O bond, for tetrafluorinated amides the additional trifluoromethyl group forces the conformation of the F–C–C=O bond to be nearly syn. [ABSTRACT FROM AUTHOR]