Mannopyranosyl uronic acid donor reactivity.

The reactivity of a variety of mannopyranosyl uronic acid donors was assessed In a set of competition experiments, in which two (S)-tolyl mannosyl donors were made to compete for a limited amount of promoter (NIS/TfOH). These experiments revealed that the reactivity of mannuronic acid donors is significantly higher than expected based on the electron-withdrawing capacity of the C-5 carboxylic acid ester function. A 4-O-acetyl-beta-(S)-tolyl mannuronic acid donor was found to have similar reactivity as per-O-benzyl-alpha-(S)-tolyl mannose.