De novo structure determination of vancomycin aglycon using the anomalous scattering of chlorine

The crystal structure of vancomycin aglycon has been determined by exploiti ng the anomalous scattering of Cl atoms present within the molecule. Real-s pace-reciprocal-space cycling with Shake-and-Bake successfully located the chlorine positions from the Bijvoet differences, even though the anomalous difference Patterson map proved to be uninterpretable. The chlorine anomalo us differences lacked sufficient phasing power to produce interpretable ele ctron-density maps. However, when combined with high-resolution native data , the chlorine positions were sufficient to determine the structure using e ither Shake-and-Bake or a tangent-formula expansion.