1 C66 2-aminoethyllysine-carbonylmethylene-cytosine 1.000 2 T66 2-aminoethyllysine-carbonylmethylene-thymine 0.885 3 CPN 2-aminoethylglycine-carbonylmethylene-cytosine 0.792 4 A66 2-aminoethyllysine-carbonylmethylene-adenine 0.786 5 40C N-[(4-amino-2-oxopyrimidin-1(2h)-yl)acetyl]-N-[(2s)-2-aminopropyl]glycine 0.760