A series of experiments was oarriod out to study the reaotions between ribonucleotides and N-acylimidazoles.In presence of morpholine-N,N'-dicyolohogyloarboxa-midine(MDCAI) or tetraethylammonium hydroxide(TEAH),the N-aoylimidazoles are found to be exoellent aoylating agents for the 3'-ribonuclootides,bnt in the absence of MDCAI or TEAH,they predominantly give 2',3'-ycloribonuoleotide with 3'-ribonuoleotide.