(NONRACEMIC) THIOLS AND ZN-II - STRUCTURAL AND CATALYTIC ASPECTS OF SOME NATURAL AND NONNATURAL ZINC THIOLATES

The catalytically active Zn-II ion of the enzyme horse river alcohol d ehydrogenase (HLADH) is well known to be co-ordinated to two thiolates and an imidazole. Attempts to prepare models of this catalytically ac tive Zn-II complex are complicated by the great tendency of Zn-II thio lates to form oligomeric structures. Some approaches to monomeric stru ctures are described. Work on this problem has led to spin-offs in the form of the use of B-aminothiols as ligands in the addition of diethy lzinc to aldehydes. Monomeric zinc complexes are believed to be the ac tive intermediates in this reaction. Excellent control over the enanti oselectivity can be obtained. Methods developed in recent years for th e synthesis of a variety of functionalized chiral nonracemic thiols op en the way to the development of a catalytic chemistry of thiols in ge neral and Zn-II thiolates in particular.