Structures of covalent adducts derived from the reactions of the 9,10-epoxides of 7,8,9,10-tetrahydrobenzo [a] pyrene and 9,10,11,12-tetrahydrobenzo [e] pyrene with DNA.

The reaction of the racemic mixture of 7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo [a] pyrene (B[a]PDE) and its enantiomer with DNA is highly stereoselective. About 90% of the adducts are derived from the former enantiomer reacting with the amino group of guanine residues. To investigate this stereoselectively we compared the reactions of 9,10-epoxy-7,8,9,10-tetrahydrobenzo [a] pyrene and 9.10-epoxy-9,10,11-12-tetrahydrobenzo [e] pyrene with DNA. Most of the stereoselectivity seen with B [a] PDE is lost. Both epoxide give mainly adducts on the N2 group of guanine by both cis and trans additions to the epoxide. Other adducts, tentatively identified as deoxyadenosine derivatives, were also detected.