Lithium hydroxide, monohydrate → 2-(Tert-butoxycarbonyl)-1-butyl-1,2,3,4-tetrahydroisoquinoline-7-carboxylic acid

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Reaction Steps

To a solution of 2-tert-butyl 7-methyl 1-butyl-3,4-dihydroisoquinoline-2,7(1H)-dicarboxylate prepared in step 2 (347 mg, 1.0 mmol) in 2:1:1 dioxane/methanol/water (6.6 mL) was added lithium hydroxide monohydrate (125 mg, 3.0 mmol) and the reaction mixture stirred 24 h at room temperature. The reaction mixture was concentrated under reduced pressure and the solid residue partitioned between ethyl acetate and water. The aqueous phase was acidified with 1 N hydrochloric acid to pH 1 and extracted several times with 3:1 chloroform/2-propanol. The combined organic phases were washed with water and saturated sodium chloride, dried (sodium sulfate), filtered, and concentrated under reduced pressure to provide 2-(tert-butoxycarbonyl)-1-butyl-1,2,3,4-tetrahydroisoquinoline-7-carboxylic acid (205 mg). ESI MS m/z 332 [M−H]−.

Provenance & Evidence