In silico anticipation of metabolic pathways extended to organic chemistry reactions: a case study with caffeine alkaline hydrolysis and the origin of camellimidazoles

Camellimidazoles A-C were recently reported as new natural substances in Keemun black tea. Although a "biosynthetic" route to these intriguing imidazole dimers was proposed from caffeine by the authors in this seminal report, we envisioned that a artefactual scenario, consisting of alkaline hydrolysis of caffeine and spontaneous cascade reactions with a methylene donor such as formaldehyde or methylene chloride, could also have led to their formation. To capture the diversity of molecules obtained under these conditions ( i. e. alkaline treatment of caffeine/formaldehyde), an in silico MetWork-based pipeline was implemented, highlighting the sought-after camellimidazoles B and C. A wealth of further compounds were also tagged, notably comprising the herein newly described and unnatural camellimidazoles D-F that were subsequently confirmed as anticipated in silico upon extensive spectroscopic analyses. Likewise, camellimidazoles B and C could also be obtained using methylene chloride as an alternative methylene donor which may also have occurred in the initial phytochemical pipeline that implied this solvent.  The current investigation emphasizes the fitness of MetWork-tagging to extend the logic of in silico anticipation of metabolic pathways to organic chemistry reactions.