Iron complexes acyl group reductions

This iron anion is a good soft nucleophile for alkyl halides and can be used twice over to produce first a monoanion with one alkyl group and then a neutral complex with two alkyl groups and four CO ligands. Each of these complexes has 18 electrons. If extra CO is added by increasing the pressure, CO inserts into one Fe—C bond to form an iron acyl complex. Finally, reductive elimination couples the acyl group to the other alkyl group in a conceptually simple ketone synthesis. It does not matter which Fe—C bond accepts the CO molecule the same unsymmetrical ketone is produced at the end. 

Polyketides form a group of diverse and structurally complex bioactive natural products. Their biosynthesis is directed by multi-domain polyketide megasynthases (PKSs), which extend the acyl chain by a series of condensation and optional reduction steps. Phylogenetic work has shown that, in a particular group of type I systems known as Irons-AT PKSs, the ketosynthase (KS) domains potentially harbour specificity towards the nature of the first four carbons of the intermediate substrate (e.g. beta-hydroxy, enoyl, methyl-branched). These results suggest a close link between KS evolution and substrate specificity. 

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