Hydrogen cyanide (HCN) generation was observed and characterized by NMR during pre-activation studies of various Fmoc-protected amino acids using diisopropyl carbodiimide (DIC) and Oxyma. Initially it was thought that a noticeable level of Fmoc de-protection was being observed resulting in the formation of dibenzofulvene (DBF) which gives a characteristic singlet in the <sup>1</sup>H NMR spectrum at around ~6.2ppm. This became a concern as any de-protection would likely result in the formation of impurities. However, after collection of additional NMR data for characterization purposes, it was revealed that this singlet was in fact HCN. The mechanism of formation was determined through characterization of a corresponding byproduct formed during the background reaction of DIC and Oxyma.

Discovery of hydrogen cyanide formation during amino acid activation studies utilizing NMR

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