Posts Tagged ‘SN’

Ritonavir: a look at a famous example of conformational polymorphism.

Monday, January 2nd, 2017

Here is an inside peek at another one of Derek Lowe’s 250 milestones in chemistry, the polymorphism of Ritonavir.[1] The story in a nutshell concerns one of a pharma company’s worst nightmares; a drug which has been successfully brought to market unexpectedly “changes” after a few years on market to a less effective form (or to use the drug term, formulation). This can happen via a phenomenon known as polymorphism, where the crystalline structure of a molecule can have more than one form. In this case, form I was formulated into soluble tablets for oral intake. During later manufacturing, a new less-soluble form appeared and “within weeks this new polymorph began to appear throughout both the bulk drug and formulation areas[1]

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References

  1. J. Bauer, S. Spanton, R. Henry, J. Quick, W. Dziki, W. Porter, and J. Morris, "Array", Pharmaceutical Research, vol. 18, pp. 859-866, 2001. http://dx.doi.org/10.1023/A:1011052932607

Bond stretch isomerism. Did this idea first surface 100 years ago?

Tuesday, February 9th, 2016

The phenomenon of bond stretch isomerism, two isomers of a compound differing predominantly in just one bond length, is one of those chemical concepts that wax and occasionally wane.[1] Here I explore such isomerism for the elements Ge, Sn and Pb.

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References

  1. J.A. Labinger, "Bond-stretch isomerism: a case study of a quiet controversy", Comptes Rendus Chimie, vol. 5, pp. 235-244, 2002. http://dx.doi.org/10.1016/S1631-0748(02)01380-2