The Crystal and Molecular Structure of Kinamycin C <i>p</i>‐Bromobenzoate

Abstract

Abstract The molecular structure of kinamycin C has been determined by means of an X‐ray study of its p ‐bromobenzoate derivative, C 31 H 23 N 2 O 11 Br. The crystals are monoclinic, P2 1 , with four molecules of the derivative and four molecules of benzene in a unit cell of dimensions: a = 18.404 ± 0.005, b = 21.299 ± 0.004, c = 9.049 ± 0.001 Å, and β = 90.07 ± 0.03°. Reflection intensities were measured visually from equi‐inclination Weissenberg photographs taken with Cu Ka radiation. The structure was solved by the heavy‐atom method, and was refined by the block‐diagonal‐matrix least‐squares method using anisotropic temperature factors for all the atoms. The final R factor is 8.9%. The stereostructures of the two crystallographically independent molecules are almost identical. The skeleton of the molecule is made up of four fused rings: two of these form a 1,4‐naphthoquinone system and the rest are a pyrrole and a cyclohexene ring. A cyano group is bonded to the nitrogen atom of the pyrrole ring, which is rather unusual in an antibiotic.