The Crystal and Molecular Structure of Bromoanhydrotetrodoic Lactone Hydrobromide

The absolute configuration of bromoanhydrotetrodoic lactone, C11H14O7N3Br, has been determined on the basis of an X-ray study of its hydrobromide. The crystals are orthorhombic, with four chemical units in a unit cell of these dimensions: a=10.88±0.04, b=15.95±0.05, and c=8.55±0.03 A; the space group is P212121. The observations for Bijvoet inequalities were made on equi-inclination integrating Weissenberg photographs taken with CuKα radiation around the a axis. On the other hand, the calculations were carried out with the parameters at the stage of the R factor of 11.9% and with anomalous dispersion correction of −0.9 for Δf′Br and 1.5 forΔf″Br . The observed and calculated inequalities for ten pairs of reflections were all in agreement with each other, so the absolute configuration was determined without any uncertainty. In addition to the X-ray determination of the absolute configuration mentioned above, the present paper will describe the details of the crystal and molecular structure.