Recognition of substituted cytosine derivatives by the base pairing with guanine connected to pyrene

The association constant between guanine and a series of cytosine derivatives in dichloromethane was determined by fluorescence quenching experiment of pyrene connected to guanine with methylene spacer. The association constant for guanine with 5-methylcytosine is found to be higher than that with cytosine. This enables us to distinguish target cytosine from its derivatives.