In vitro Dimroth rearrangement of 1-(2-carboxyethyl) adenine to N6-(2-carboxyethyl)adenine in single-stranded calf thymus DNA

Abstract

The new adduct N 6-(2-carboxyethyl)adenine ( N 6-CEA) was prepared from 1-(2-carboxyethyl)adenine (1-CEA) by base catalyzed (Dimroth) rearrangement of 1-CEA. The structure of N 6-CEA was assigned on the basis of UV spectra and electron impact and isobutane chemical ionization mass spectra. When the carcinogen β-propiolactone was reacted in vitro with calf thymus DNA, 1-CEA but not N 6-CEA was detected on paper chromatograms following acid hydrolysis of the DNA. When BPL-reacted single-stranded DNA was incubated at pH 11.7 (37°C, 18 h) prior to acid hydrolysis, it was found that 1-CEA was completely converted to N 6-CEA in DNA by Dimroth rearrangement, whereas no conversion occurred at pH 7.5. The extent of Dimroth rearrangement at various pHs and temperatures was determined for 1-CEA, 1-methyladenine (1-MeA), 1-(2-carboxyethyl)-deoxyadenosine-5′-monophosphoric acid (1-CEdAdo5′P) and the phosphodiester 5′- O-(2-carboxyethyl)phosphono-1-(2-carboxyethyl)deoxyadenosine (1-CE-dAdo-5′-P-CE).