Copper coordination chemistry of the patellamides – cyanobactins in the ascidian-Prochloron symbiosis

Abstract

Prochloron didemni, an obligate symbiont of certain ascidians (sea squirts found in tropical areas), produces various cyclic pseudo-octapeptides in large quantities. These secondary metabolites have attracted the attention of medicinal chemists and, due to their four azol(in)e and four amide donor groups, coordination chemists have become interested in these molecules. The structures of the metal-free macrocycles and their dinuclear copper(II) complexes are known, and solution equilibria, spectroscopic properties and a range of biologically relevant reactions have been studied in detail. However, until recently, the properties of the patellamides and structures of the copper(II) complexes in living systems have not been known unambiguously. These are reviewed in the present Perspective and, as a result, it now is possible to discuss possible biological functions of these species.