Abstract
An improved synthetic approach to tenatoprazole 1 is described. It started from 2,3,5‐trimethyl‐4‐nitropyridine‐N‐oxide 2 with acetic anhydride via rearrangement and hydrolysis to give 3, Chlorination with SOCl2 yielded 2‐chloromethyl‐3,5‐dimethyl‐4‐nitropyridine hydrochloride 4, then 4 condensed with 2‐mercapto‐5‐methoxy imidazole [4,5‐b]pyridine 5 to give 5‐methoxy‐2‐[(4‐nitro‐3,5‐dimethyl‐2‐pyridinyl)methylthio]imidazole[4,5‐b]pyridine 6. At last the title compound 1 was produced by two methods: 6 was oxidized with MCPBA and then methoxylated with CH3ONa to give 1 and 6 was first methoxylated with CH3ONa and then oxidized with MCPBA to give 1. The overall yield is around 26% for both five‐step syntheses.
Acknowledgment
The authors thank the management of Zhejiang Shangyu Sanhe Pharmachem Co., Ltd., for financial assistance. We also thank Yuanjiang Pan for his assistance on 1H NMR work.