Heteroaromatic monothiocarboxylic acids from Pseudomonas spp

Pyridine derivatives substituted with monothiocarboxylic acid groups are the uniquemetabolites of certain Pseudomonas species. Pyridine-2,6-di-(monothiocarboxylic acid) 1a was found during a screening program for antibiotically active bacterial metabolites due to its ability to complex Fe³⁺. The structure of this complex, itsredox behavior and the biogenesis of the ligand molecule were studied in detail. Thislead to the discovery of a new class of natural products, viz. acylsulfenic acid derivatives. Interest in 1a was revived shortly when complexes with other metals were studied as models for sulfur-containing enzymes. It could also be shown that a quinoline monothiocarboxylic acid derivative acted as an alternative siderophorefor Pseudomonas fluorescens. But a real renaissance was observed only whenthe role of 1a in the degradation of CCl₄ by Pseudomonas stutzeri became evident.