ABSTRACT

Installation of the amide linkage into amino sugar substrates is an important task in carbohydrate chemistry, particularly for the synthesis of naturally occurring glycosyl amides and novel glycomimetics. 1 The original reaction of phenyl azide with a phosphane, to generate the aza-ylide, 2 discovered by Staudinger opened avenues to subsequent chemistry from aza-Wittig reactions and amide ligations, by treatment with aldehydes and ketones or acyl derivatives, respectively. A wide variety of phosphanes have since been employed in this context, ranging from the ubiquitous PPh3, to lower molecular weight variants, such as PMe3 and P(n-Bu)3, as well as the more recent examples of aryl phosphanes used in traceless Staudinger ligations. 3 While these materials work efficiently to provide good yields of the desired amides, they each have drawbacks that limit their use. For example, PPh3 forms an oxide byproduct (O=PPh3) that is notoriously difficult to separate by chromatography due to it streaking on silica gel. The lower molecular weight phosphanes tend to be liquids with unpleasant odors, and the more functionalized phosphanes used in modern traceless ligation reactions are somewhat expensive to produce.