the bridge containing only two carbon atoms

Full Title

Heterocyclic compounds containing 4aH-8, 9 c- Iminoethano-phenanthro [4, 5-b, c, d] furan ring systems, e.g. derivatives of [4, 5-epoxy]-morphinan of the formula: [IMAGE cpc-sch-C07D-0991.gif] > containing 4aH-8, 9 c-Iminoethano- phenanthro [4, 5-b, c, d] furan ring systems condensed with carbocyclic rings or ring systems > with a bridge between positions 6 and 14 > the bridge containing only two carbon atoms