Rebamipide
(1) is a superior drug compared to existing
drugs for use in healing of peptic ulcers, gastrointestinal bleeding,
and dyspepsia. It is also useful as an ophthalmic drug for the treatment
of dry eye syndrome. Process intensification for its synthesis was
achieved by (i) averting uncontrollable frothing using Krapcho decarboxylation
instead of conventional acid hydrolysis, where uncontrollable frothing
became chaotic, (ii) minimizing organic waste generation by using
a single organic solvent, and (iii) avoiding anti-foaming agents (n-octanol, acetophenone) and acetic acid. With these trifling
modifications, the overall yield of active pharmaceutical ingredient
(API) was ≥83% with excellent purity (≥99.89%), and
the process meets the metrics of “green” chemistry with
an E-factor = 11.5. The developed hassle-free commercial
process is viable for multi-kilogram synthesis of Rebamipide (1) as the key step, Krapcho decarboxylation is safe to run
at 130–140 °C in DMSO, and it was proved to be effective
by differential scanning calorimetry thermal screening studies. The
characterization data of intermediates, process-related impurities,
and API are reported. The carryover and process-related impurities
were controlled efficiently. The present work can enhance the scope
and worldwide adoptability of Rebamipide (1), which is
currently limited to Asian countries.
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