Antiviral glyoxal derivative. Specifically reacts with unpaired guanine residues of nucleic acids. Prepn: L. Rappen, J. Prakt. Chem. 157, 177 (1941); and antiviral activity: B. D. Tiffany et al., J. Am. Chem. Soc. 79, 1682 (1957). Reaction with guanine residues: M. Staehelin, Biochim. Biophys. Acta 31, 448 (1959); R. Shapiro, J. Hachmann, Biochemistry 5, 2799 (1966). Use as RNA probe: M. Litt, V. Hancock, ibid. 6, 1848 (1967); M. Balzer, R. Wagner, Anal. Biochem. 256, 240 (1998). Use in peptide mapping to identifiy arginine residues: O. T. Akinsiku et al., J. Mass Spectrom. 40, 1372 (2005).