Reaction of O-nucleosid-5'-yl (or 3'-yl) O-alkyl H-phosphonate diesters wit
h L-lysine methyl ester dihydrochlorides in the presence of Et3N and CCl4 p
roduced the corresponding N-alpha, N-epsilon- lysine linked 5', 5'(or 3', 3
')-dinucleotides in excellent yield.