Lithium hydroxide, monohydrate → 1-[4'-(2"-Ethyl-5",7"-dimethylimidazo[4,5-b]pyridin-3-yl)methylphenyl]cyclopent-3-ene-1-carboxylic acid

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Reaction Steps

A solution of the product of Step 5, above (5.76 g, 14.9 mmol) and lithium hydroxide monohydrate (6.23 g, 148 mmol) in 148 ml of methanol and 148 ml of water was heated at reflux for 2 hours. The reaction was then concentrated in vacuo, the residue was taken up in water and the pH was adjusted to 4 with concentrated HCl when the title compound precipitated as a colorless solid which was filtered off, dried in vacuo and recrystallized first from ethyl acetate/methanol, then from methanol to yield 1.9 g of title compound which was contaminated with 2.5% of 1-[4'-(2"-ethyl-5",7"-dimethylimidazo[4,5-b]pyridin-3-yl)methylphenyl]-2-vinylcyclopropane-1-carboxylic acid. Another recrystallization from methanol yielded 1.5 g of title compound, mp 232°-233° C., now about 98.3% pure, as determined by reverse-phase HPLC using a C-18 Beckman 25 cm long column and 30% pH 2.3 phosphate buffer in acetonitrile as eluant.

Provenance & Evidence