SYNTHESIS OF ENTEROCHELIN

Enterochelin (enterobactin), the cyclic trilactone of N-(2,3-dihydroxy benzoyl)-L-serine 6, an important enterobacterial iron-transporting co mpound, has been synthesised from N,N;dibenzyl-L-serine 2 in four step s. The protected amino acid was oligomerised using N,N-dicyclohexylcar bodiimide in a high-dilution procedure yielding a mixture of di-, tri- and tetra-lactones, The trilactone 3b was deprotected by hydrogenolys is and the resultant amine 4 was acylated with 2,3-dibenzyloxybenzoyl chloride to yield hexa-O-benzylenterochelin 5. This upon hydrogenolysi s gave enterochelin in moderate yield.