Sulfonylation sites for adenine and its nucleosides/nucleotides

Sulfonylation is extensively used to label DNA and RNA, assess their interactions and quantify components including nucleobases and nucleosides/nucleotides although the sulfonylation sites remain controversial. Here, we systematically investigated the sulfonylation of adenine and its nucleosides/nucleotides with 5-(dimethylamino)-naphthalene-1-sulfonyl chloride (DNS-Cl), 5-(diethylamino)-naphthalene-1-sulfonyl chloride (DEANS-Cl), and 5-((N,N-diethylleucyl) amino)-naphthalene-1-sulfonyl chloride (DELANS-Cl). Detailed spectral analysis with nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS) showed similar sulfonylation behaviors among the reagents. For adenine, its secondary amine in the imidazole ring (N⁹H) sulfonylated more readily than the exocyclic amino group (N6H2). For adenosine and its nucleotides, the 2'-OH group in the ribosyl moiety was preferably sulfonylated whereas the 3'-OH was the preferred site for 2'-deoxyadenosine and its nucleotides. Alkylation and amidation of the aromatic amino group in these 5-aminonaphthalene-1-sulfonyl chlorides did not influence the sulfonylation preferences. This offered a reliable approach and comprehensive details of such sites for adenine and its nucleosides/nucleotides.