Synthesis of enterochelin

Abstract

Enterochelin (enterobactin), the cyclic trilactone of N-(2,3-dihydroxybenzoyl)-L-serine 6, an important enterobacterial iron-transporting compound, has been synthesised from N,N-dibenzyl-L-serine 2 in four steps. The protected amino acid was oligomerised using N,N–dicyclohexylcarbodiimide in a high-dilution procedure yielding a mixture of di-, tri- and tetra-lactones. The trilactone 3b was deprotected by hydrogenolysis and the resultant amine 4 was acylated with 2,3-dibenzyloxybenzoyl chloride to yield hexa-O-benzylenterochelin 5. This upon hydrogenolysis gave enterochelin in moderate yield.