Lithium Hydroxide → 18-Ethoxymethoxy-14-(4-methoxy-benzyl)-2,15-dioxo-3,14,16-triaza-tricyclo[14.3.0.0*4,6*]nonadec-7-ene-4-carboxylic acid

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Reaction Steps

A solution of the ester 21g (0.775 g, 1.39 mmol) in 1:1:1 THF-Methanol-aq. 1M LiOH (36 ml) was stirred at rt for 3.5 h after which TLC (95:5 and 9:1 dichloromethane-methanol) and LC-MS indicated complete conversion into the carboxylic acid. The reaction mixture was then concentrated into approximately ⅓ of the volume, then diluted with water (10 ml) and acidified to approx. pH 4 using aq. 10% citric acid (60 ml) upon which a precipitate formed. The mixture was washed with ethyl acetate (3×25 ml) and the combined organic layers were washed with brine (2×50 ml), then dried (Na2SO4), filtered and concentrated. The residue was concentrated from toluene (3×10 ml) which gave the crude title compound as an off-white foam (0.75 g, quantitative). LR-MS: Calcd for C28H40N3O7: 530. Found: 530 [M−H].

Provenance & Evidence