An Improved Stereocontrolled Synthesis of Pyochelin, Siderophore of Pseudomonas aeruginosa and Burkholderia cepacia

A considerably improved stereocontrolled synthesis of pyochelin, a hydroxyphenylthiazolinylthiazolidine type of siderophore common to most strains of Pseudomonas aeruginosa and Burkholderia cepacia is described. 2′-(2-Hydroxyphenyl)-2′-thiazoline-4′-carboxaldehyde, a key molecule involved in this synthesis has been prepared by reduction of 2′-(2-hydroxyphenyl)-2′-thiazoline-4′-(N-methoxy,N-methyl) carboxamide with lithium aluminium hydride. The aldehyde was further coupled with (R)-N-methylcysteine to yield pyochelin. Under the conditions reported, epimerization at the C-4′ center was considerably diminished.