(Nonracemic) thiols and ZnII. Structural and catalytic aspects of some natural and non-natural zinc thiolates

Abstract

The catalytically active Zn^II ion of the enzyme horse liver alcohol dehydrogenase (HLADH) is well known to be co-ordinated to two thiolates and an imidazole. Attempts to prepare models of this catalytically active Z^II complex are complicated by the great tendency of Zn^II thiolates to form oligomeric structures. Some approaches to monomeric structures are described. Work on this problem has led to spin-offs in the form of the use of β-aminothiols as ligands in the addition of diethylzinc to aldehydes. Monomeric zinc complexes are believed to be the active intermediates in this reaction. Excellent control over the enantioselectivity can be obtained. Methods developed in recent years for the synthesis of a variety of functionalized chiral nonracemic thiols open the way to the development of a catalytic chemistry of thiols in general and Zn^II thiolates in particular.