Studies on the syntheses of heterocyclic compounds. Part CDVIII. Crystal structure of capaurimine mono-p-bromobenzoate

Abstract

The crystal structure and absolute configuration of capaurimine mono-p-bromobenzoate, C₂₇H₂₆O₆NBr, have been determined by a three-dimensional X-ray analysis. The crystals are monoclinic, space group P2₁, with Z= 2 in a unit cell of dimensions a= 13·18, b= 7·71, c= 13·37 Å, β= 117·0°. The structure was determined by the heavy-atom method and refined by least-squares methods using 1780 observed reflexions to R 0·109. The absolute configuration was also determined by use of the anomalous dispersion effect of the bromine atom. Capaurimine, 13a(S)-5,6,13,13a-tetrahydro-1,10-dihydroxy-2,3,9-trimethoxy-8Hdibenzo[a,g]quinolizine, takes a cis-conformation in the quinolizidine ring. The molecules are connected by N ⋯ H–O (N ⋯ O 2·74 Å) hydrogen bonds along the b axis.