RESUMO
Strategies for the formation of carbon-carbon bonds from the α-thioaryl carbonyl products of substituted lactams are described. Although direct functionalization is possible, a two step process of oxidation and magnesium-sulfoxide exchange has proven optimal. The oxidation step results in the formation of two diastereomers that exhibit markedly different levels of stability toward elimination, which is rationalized on the basis of quantum mechanical calculations and X-ray crystallography. Treatment of the sulfoxide with i-PrMgCl results in the formation of a magnesium enolate that will undergo an intramolecular Michael addition reaction to form two new stereogenic centers. The relationship between the substitution patterns of the sulfoxide substrate and the efficiency of the magnesium exchange reaction are also described.
Assuntos
Carbono/química , Compostos Heterocíclicos/química , Compostos Heterocíclicos/síntese química , Catálise , Cristalografia por Raios X , Estrutura MolecularRESUMO
Two approaches are presented for the synthesis of the macrolide core of the mycolactone polyketides. The first intertwines ring closing metathesis (RCM) within a two-step Julia olefination protocol, while the second intercepts the optimized routes of Kishi, thereby providing formal access to the mycolactones.
Assuntos
Toxinas Bacterianas/química , Toxinas Bacterianas/síntese química , Alcenos , Macrolídeos , Mycobacterium/químicaRESUMO
Interest in multicomponent reactions (MCRs) has surged during the past two decades as interest in the efficient synthesis of small molecule libraries has gained prominence. MCRs fill an important niche in library synthesis by providing direct access to library compounds and by serving as starting points for Diversity-Oriented Synthesis (DOS). Recent advances in the area of MCR chemistry have included the discovery of new reactions, development of the first asymmetric catalysts, and the application of MCRs to natural products and other targets of biological interest. This review will highlight recent developments in MCRs as a rich source of molecular diversity.
