The 4, 5-epoxy-10-normorphinans 2a and 2b featuring the morphine skeleton lacking the B- ring were synthesized using the “nitrous acid deamination” of indolenines as the key step. Thus, indolenines 13 and 15 were prepared by Fischer synthesis from the corresponding bicyclic ketolactams 6 and 12, respectively, and further transformed into the related hexahydrodibenzofurans. Ketolactam 6 was obtained from 3-nitromethylcyclohexanone ...