The cyclic phosphoramidite reagent c-PyPA enables iterative polyphosphorylations.

An iterative polyphosphorylation approach is described, which is based on a phosphoramidite (P-amidite) derived reagent (c-PyPA) obtained from the cyclization of pyrophosphate with a reactive diisopropylamino dichlorophosphine. This type of reagent is unprecedented as it represents a reactive P-amidite without protecting groups. The reagent proved to be stable in solution over several weeks. Its utility is described in the context of iterative monodirectional and bidirectional polyphosphorylations. The ensuing functionalized cyclotriphosphate can be opened with a variety of nucleophiles providing ready access to diverse functionalized polyphosphate chains of defined length with several tags, including both P-N and P-O labels. Their interaction with exo- and endopolyphosphatases is described.