2D NMR experiments at 60 MHz: COSY-90 and COSY-45

In December 2016 it was widely reported† that students from Sydney Grammar School reproduced the drug Daraprim®, also known as pyrimethamine. The students followed a reaction pathway to produce it, and the final product was analysed at the University of Sydney, School of Chemistry (200 MHz ¹H NMR spectrum). This substance is used as an example to illustrate 60 MHz NMR spectrometer performance, and the difference between the two-dimensional (2D) experiments, COSY-90 and COSY-45.