A methodology for the synthesis of oligophosphate conjugates using phosphordiamidites is described. This strategy facilitates the straightforward preparation of C2-symmetric dinucleoside tri-, penta-, and heptaphosphates. Moreover, unsymmetric compounds such as thiamine adenosine triphosphate and thiamine cytidine triphosphate can be prepared. The material is used to study the inhibitory activity of thiaminylated nucleotides against adenosine diphosphate ribosyltransferases.