Second generation synthesis of the anti-infective natural product gallinamide A

Gallinamide A is a depsipeptide natural product produced by cyanobacteria that possesses potent anti-parasitic activity through the inhibition of essential cysteine protease enzymes. Recently, gallinamide A was also shown to possess potent antiviral activity against SARS-CoV-2 via the covalent inhibition of the host cysteine protease cathepsin L that plays a role in viral entry. In order to perform detailed pre-clinical studies on gallinamide A as a potential antiviral for COVID-19, access to significant quantities of the natural product was necessary and required the design of a more efficient synthetic route to the natural product. Herein, we describe a second generation total synthesis of gallinamide A that delivered the natural product on a 315 mg scale over 16 total steps (9 steps in the longest linear sequence) in an overall yield of 32%.