O[Li].O.CO.[NH:6]([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[C@H:7]([C:9]([NH:11][C@H:12]([C:14]([O:16]C)=[O:15])[CH3:13])=[O:10])[CH3:8].C(O)(=O)CC(CC(O)=O)(C(O)=O)O>O>[NH:6]([C:18]([O:20][C:21]([CH3:23])([CH3:22])[CH3:24])=[O:19])[C@H:7]([C:9]([NH:11][C@H:12]([C:14]([OH:16])=[O:15])[CH3:13])=[O:10])[CH3:8]To a solution of LiOH.H2O (275 mg, 6.56 mmol) in a mixture of solvents MeOH:H2O (10.9 mL:3.6 mL) was added Boc-Ala-Ala-OMe (1.2 g, 4.38 mmol) and stirred for 4 hours at r.t. The solution was acidified to pH 2 with saturated aqueous solution of citric acid and the mixture was extracted with EtOAc (3×20 mL). The organic layer was dried over Na2SO4 and concentrated under vacuum to give the desired product Boc-Ala-Ala-OH as a highly viscous and hygroscopic oil in quantitative yields (1.14 g). The product was taken for further reactions directly without any purification.
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