Chemical Synthesis of Cap Analogues: P1,P2-Dinucleoside-5′-diphosphates

Abstract
A procedure was developed for the chemical synthesis of P1,P2-dinucleoside-5''-diphosphates (N1(5'')pp(5'')N2) on a nanomolar scale. Reaction conditions for activating purine-5''-monophosphates (pA, pG and pm G) by 1,1''-carbonyldiimidazole were studied and optimized in respect to solvents and amount of activating reagent used. Various dinucleosie-5''-diphosphates were synthesized in 62-98% yield by incubating activated and non-activated purine-5''-monophosphates. Two unexpected by-products were formed by competition reactions: the imidazolidate of the non-activated nucleotide and the corresponding symmetrically substituted dinucleoside-5''-diphosphate. A mechanism is proposed to explain the observed side reactions.