Structure of a modified β-lactam antibiotic

1-Phenoxy-9b-phenyl-1,4,5,9b-tetrahydro-2H-azeto[1, 2-a]isoquinolin-2-one, C23H19NO2, is a carbocyclic analogue of cephalosporin. The crystals are monoclinic, M(r) = 341, C2/c, a = 23.054 (1), b = 7.315 (2), c = 23.713 (4) angstrom, beta = 115.08 (6)-degrees, V = 3621.9 angstrom-3, Z = 8, D(m) = 1.24, D(x) = 1.25 g cm-3, lambda-(Cu K-alpha) = 1.5418 angstrom, mu = 5.96 cm-1, F(000) = 1440, T = 288 K, final R = 0.071 for 2450 observed reflections. The beta-lactam N atom, N(7), is 0.229 angstrom away from mean plane containing C(11), C(5) and C(25). From the plane N(7)-C(5)-C(11)-C(3), atoms O(2) and O(1) are in the trans position whereas O(1) and C(8) are in the cis position. The crystal structure is stabilized by base-base interactions about the center of inversion.