A. Glendinning et al., STRUCTURE OF [2]BENZOXEPINO[4,3-B]INDOLE, Acta crystallographica. Section C, Crystal structure communications, 49, 1993, pp. 2126-2128
The crystal structure of [2]benzoxepino[4,3-b]indole, (2), shows that
this tetracyclic molecule comprises two essentially flat 'wings', the
indole and benzene aromatic moieties, linked via a 'hinge' comprising
the CH2O and carbonyl groups, and producing a butterfly shape; the ang
le between the wings is 29.2 (7)-degrees.