SYNTHESIS OF OLIGONUCLEOTIDE ADDUCTS OF THE BAY-REGION DIOL EPOXIDE METABOLITES OF CARCINOGENIC POLYCYCLIC AROMATIC-HYDROCARBONS

An efficient method for the site-specific synthesis of adducts between the biologically active diol epoxide metabolites of carcinogenic polycyclic aromatic hydrocarbons (PAHs) and oligonucleotides in which a PAH component of predetermined stereochemistry is linked covalently to the exocyclic amino groups of deoxyadenosine (dA) and deoxyguanosine (dG) is described. The synthetic strategy involves in the key step coupling a protected halopurine derivative with an amino derivative (or an aminotriol derivative) of the PAH. This method was initially employed to prepare the dA and dG adducts of the model PAH 1-methylpyrene. The appropriately protected dA adduct was then incorporated into the oligonucleotide sequence d(GCAGGTCA(*)AGAG) where A(*) represents N6-pyrenylmethyl-dA. This methodology was extended to the synthesis of trans adducts of anti-diol epoxide metabolites of benzo[a]pyrene and 5-methylchrysene linked to the 6-amino function of dA. The parent hydrocarbons are widespread environmental carcinogens. This synthetic approach, dubbed the total synthesis method, complements the direct synthesis method which involves the direct reaction of PAH diol epoxides with oligonucleotides. The total synthesis method is broader in scope than the latter, and it is readily adaptable to the large scale preparation of PAH-oligonucleotide adducts required for structure determination by high resolution NMR and X-ray crystallographic techniques.