Reactions of 'bay-region' and non-'bay-region' diol-epoxides of benz(a)anthracene with DNA: evidence indicating that the major products are hydrocarbon-N2-guanine adducts.

The rates of reaction and the products formed when two vicinal diol-epoxides derived from benz(a)anthracene, anti-BA-3,4-diol 1,2-oxide (t-3,r-4-dihydroxy-t-1,2-oxy-1,2,3,4-tetrahydrobenz(a) anthracene)* and anti-BA-8,9-diol 10,11-oxide (r-8,t-9-dihydroxy-t-10,11-oxy-8,9,10,11-tetrahydrobenz(a)anthracene) reacted with DNA were studied in vitro and the results were compared with those obtained in similar experiments using anti-BP-7,8-diol 9,10-oxide (r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo(a)pyrene). The reactivities appeared to decrease in the order anti-BP-7,8-diol 9,10-oxide > anti-BA-3,4-diol 1,2-oxide > anti-BA-8,9-diol 10,11-oxide. The diol-epoxides reacted to a similar extent with single- and with double-stranded DNA but reactions with dGMP, at equivalent concentrations, were much slower than with DNA. With the diol-epoxides of benz(a)anthracene, two principal adducts were present in DNA hydrolysates and evidence was obtained, based on pK determinations before and after nitrous acid treatment, consistent with their being N2-guanine derivatives, analogous to the known DNA-reaction products of benzo(a)pyrene 7,8-diol 9,10-oxide.