Abstract Synthesis of the two isomers 2, 3 of the mono coenzyme A ester of o- succinylbenzoic acid (1, OSB, ie 4-(2-carboxyphenyl)-4-oxobutanoic acid) and enzymic conversion of 3, to 1, 4-dihydroxy-2-naphthoic acid 7 shows that as opposed to previous assumptions the “aliphatic” rather than the “aromatic” carboxyl group in o-succinylbenzoic acid 1 is activated during vitamin K 2 biosynthesis in Escherichia coli and Mycobacterium ...