Chemoselective Saponification in the Synthesis of Danuglipron Facilitated with Trifluoroethanol

Danuglipron (PF-06882961), a potent, orally bioavailable small-molecule glucagon-like peptide-1 receptor (GLP-1R) agonist, is currently being developed for glycemic control among patients with Type-2 diabetes (J. Med. Chem. 2022, 65, 8208–8226; JAMA Netw. Open. 2023; 6(5): e2314493). The earlier synthesis of danuglipron suffered from chemoselective issues due to the competing nitrile hydrolysis in the final saponification step, which resulted in highly convoluted operations and extensive chromatographic purifications. We found that the methyl ester could be converted to trifluoroethyl ester, and the latter underwent hydrolysis to carboxylic acid in a much cleaner reaction profile. A thorough design of experiments (DOE) was conducted to expand the operating time window of the process to aid the process robustness during manufacturing. The improved process increased the yield by ∼20% and reduced the process mass intensity (PMI) by 86%.