ABSTRACT
An efficient synthesis of potentially carcinogenic dibenzo[a,l]tetracene 1 and dibenzo[a,j]tetracene 2 has been developed and the synthetic standards were used to establish their environmental presence. The synthesis involves Diels–Alder reaction of in situ generated ortho-quinodimethane with phenanthrene-1,4-dione, followed by reductive aromatization as key steps. This synthetic strategy resulted in good overall yield and the mixture of 1 and 2 is easily separable by reversed-phase liquid chromatography (RP-LC). Compounds 1 and 2 were identified in a complex mixture of polycyclic aromatic hydrocarbons from coal tar (Standard Reference Material 1597a) and thus could be potential environmental hazards.
Funding
The authors thank the Department of Pharmacology and Penn State Cancer Institute, Penn State College of Medicine for financial support.