[CH:1]([NH:3][C:4]1[S:5][CH:6]=[C:7]([C:9](=[O:13])[C:10]([OH:12])=[O:11])[N:8]=1)=[O:2].C(=O)(O)[O-].[Na+].C(OCC)C.[BH4-].[Na+]>O>[OH:13][CH:9]([C:7]1[N:8]=[C:4]([NH:3][CH:1]=[O:2])[S:5][CH:6]=1)[C:10]([OH:12])=[O:11]To a suspension of 2-(2-formylamino-1,3-thiazol-4-yl)glyoxylic acid, which can be represented as 2-(2-formylimino-2,3-dihydro-1,3-thiazol-4-yl)glyoxylic acid, (20 g.) in water (400 ml.) was added sodium bicarbonate (8.4 g.) under ice-cooling and stirring, and the mixture was stirred for 10 minutes at the same temperature, and then diethyl ether (10 ml.) was added thereto. To the mixture was added sodium borohydride (1.52 g.) over 10 minutes with stirring at the same temperature, and the mixture was stirred for 1 hour and 50 minutes at the same temperature. After the reaction, the reaction mixture was filtered. The filtrate was adjusted to pH 4.0 with 10% hydrochloric acid and then concentrated under reduced pressure till the volume became 100 ml. The concentrated filtrate was adjusted to pH 1 with 10% hydrochloric acid, and crystallization was induced by scratching. The concentrated filtrate was stirred for 1 hour at room temperature and then allowed to stand overnight in a refrigerator. The precipitates were collected by filtration, washed with ice-water twice and then dried under suction to give 2-hydroxy-2-(2-formylamino-1,3-thiazol-4-yl)acetic acid, which can be represented as 2-hydroxy-2-(2-formylimino-2,3-dihydro-1,3-thiazol-4-yl)acetic acid, (14.8 g.), mp. 188° to 189° C. (dec.).
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