PURPOSE: To obtain the subject compound, by treatment of a 2,3- dihydroxybenzoic acid or its salt with 2,3-dihydroxybenzoate-3,4-dioxygenase in a specific liquid medium, followed by the reaction with a source of ammonia or a primary amine.
CONSTITUTION: A 2,3-dihydroxybenzoic acid of formula I (R1 and R2 are each H, alkyl, alkoxy, halogen, mercapto, phenyl or phenoxy; R3 is H or alkyl; R2 and R3 together form a residue of an aromatic ring fused to the pyridine ring) is treated with 2,3-dihydroxybenzoate-3,4-dioxygenase in a liquid medium which lacks active decarboxylase and which has a pH of 4-9, an ionic strength below about 1 mole, and a low concentration of metal cations and complex anions, thereby to accumulate the 2-hydroxy-3-carboxymuconic acid semialdehyde, which is allowed to react with a source of ammonia or a primary amine to give a pyridine-2,3-dicarboxylic acid of formula II useful as an intermediate for herbicides.
JIYOOJI DABURIYU MATSUCHIYAMU
DEIBITSUDO AI SUTAARINGU
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