Minor products from the reaction of (+) and (−) benzo[a]-pyrene-anti-diolepoxide with DNA

The reaction of trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BP-diolepoxide) with deoxyguanosine has been studied. In addition to the expected N2-guanine derivative minor products resulting from reaction at the O6 and 7-positions have been identified. Reaction of racemic, (+) or (-) BP-diolepoxide with [14C] and [3H]purine labelled DNA allowed these same products to be identified and their yields estimated. It was found that the O6 and 7-guanine products were derived mainly from reaction of the (-)isomer. The 7-substituted guanine derivative in DNA was unstable, undergoing either spontaneous release of the substituted guanine or imidazole ring opening.