SYNTHESIS OF DINUCLEOTIDES CONTAINING A BRIDGED NONCHIRAL INTERNUCLEOTIDE 5'-PHOSPHORAMIDATE OR 3'-PHOSPHORAMIDATE LINKAGE

The synthesis of several dinucleoside phosphate derivatives which are linked by phosphoramidate bands [3'-O-P(=O)(O)-NH-5' or 3'-NH-P(=O)(O)-O-5'] has been accomplished. The internucleoside phosphoramidate linkage was performed using the Staudinger reaction which is directly followed by a Michaelis-Arbuzov type transformation. Due to the exclusive use of base labile blocking groups deprotection could be carried out very easily in a single step by treatment with concentrated ammonia for 24 hours at 55 degrees C.