Ambiguous aspirin

AspirinTwo back-to-back papers in the well-known chemistry journal Angewandte Chemie recently could have potentially serious consequences for the pharmaceutical industry, because they reveal what the authors claim are inherent ambiguities in the crystalline forms of aspirin.

A team of scientists from Denmark, Germany, and India suggest that the recently reported form II of the ubiquitous pharmaceutical may indeed exist but the crystallographic evidence could just as readily be interpreted as being from a single crystal of form I. The findings could have implications for patent arguments over novel forms of the purportedly generic drug.

Even from the early days of crystal studies into aspirin, there were serious issues surrounding its structure. PJ Wheatley obtained the first crystal structure in 1964, but certainly not without a degree of ambiguity. “After Wheatley, Chick Wilson got very high R-factors in his neutron study of 2000,” Desiraju told SpectroscopyNOW.com, “this is what was nagging me throughout, why were these R-factors so high?” Desiraju and his colleagues suggest that the Zaworotko study does not represent much of an improvement on the precision of these earlier studies and moreover confounds attempts to define a new polymorphic form of aspirin.

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