Aminoacyl derivatives of nucleosides, nucleotides, and polynucleotides. III. Reaction of N-benzyloxycarbonylglycine ethyl orthoester with uridylyl-(3'→5')-uridine or cytidylyl-(3'→5')-adenosine; An alternate approach to the synthesis of 2'(3')-O-glycyl diribonucleoside phosphates