[OH-].[Na+].C[O:4][C:5]([C:7]1[CH:12]=[N:11][C:10]([N:13]2[CH2:17][CH2:16][CH2:15][CH2:14]2)=[C:9]([O:18][CH2:19][CH:20]2[CH2:23][CH2:22][CH2:21]2)[N:8]=1)=[O:6].CO>O1CCCC1>[CH:20]1([CH2:19][O:18][C:9]2[N:8]=[C:7]([C:5]([OH:6])=[O:4])[CH:12]=[N:11][C:10]=2[N:13]2[CH2:17][CH2:16][CH2:15][CH2:14]2)[CH2:23][CH2:22][CH2:21]1Sodium hydroxide 2M (10 mL) was added to a solution of the 6-cyclobutylmethoxy-5-pyrrolidin-1-yl-pyrazine-2-carboxylic acid methyl ester (2.2 g, 7.4 mmol) in a (1:1) mixture of methanol and tetrahydrofuran (30 mL), the reaction mixture was stirred at room temperature for 2 hours. The reaction mixture was concentrated in vacuo and the residue was dissolved in ether (30 mL) and extracted with water (50 mL), the aqueous layer was washed with ether (2×50 mL) until only product remained in the aqueous layer. The aqueous layer was cooled to 0° C. and acidified with concentrated hydrochloric acid until precipitation was observed. The precipitate was filtered and dried in vacuo to afford 6-cyclobutylmethoxy-5-pyrrolidin-1-yl-pyrazine-2-carboxylic acid as a cream solid 1.65 g (80% yield) LC@215 nm; Rt 1.98: 93%, m/z (ES+): 278 (M+H).
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