Synthesis and Mutagenicity of Some Benzo[g]- and Indeno[a]phenanthrenes

The synthesis of two aromatic ketones 7(H)-indeno[2,1-a]phenanthren-7-one and 11(H)-indeno[1,2-a]phenanthren-11-one by Diels-Alder cycloaddition of 1-vinyl-3,4-dihydro-naphthalene with inden-1-one generated in situ from 3-bromo-indan-1-one and triethylamine, followed by dehydrogenation-aromatization reaction of the cycloadducts, is reported. Further the synthesis of 7(H)-indeno[2,1-a]phenanthrene, 11(H)-indeno[1,2-a]phenanthrene, 9(H)-benzo[g]indeno[2,1-a]phenanthrene and 13(H)-benzo[g]indeno[1,2-a]phenanthrene by a procedure based on the reduction of the corresponding cycloadducts followed by a dehydration-aromatization reaction is presented. The assignments of the structure by 1H- and 13C-NMR spectroscopy is discussed. Estimates of the mutagenic activity of the compounds in Salmonella typhymurium determined by Ames' test show that three compounds are mutagenic for TA 98 strain and four for TA 100 strain. The mutagenic activities exhibited by these compounds are compared with those shown by cyclopenta[a]phenanthrenes. The effect of benzoannulation on cyclopenta[a]phenanthrenes and related cyclopenta[a]phenanthrenones is discussed.