Strong Hydrogen Bonding to the Amide Nitrogen Atom in an "Amide Proton Sponge": Consequences for Structure and Reactivity.

N-Protonated amides have been proposed as intermediates in several biologically important reactions, but they have yet to be identified spectroscopically. The first step toward this goal is now reported in the form of spectroscopic and crystallographic proof of a strong intramolecular hydrogen bond between a charged proton donor and an amide nitrogen atom in the "proton sponge" derivative 1; novel reactivity results from this interaction. TfO-= trifluoromethanesulfonate. © 1999 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.