C–C Bond Formation and Decarboxylation

Carbon–carbon forming reactions have always been the mainstay of conventional synthetic organic chemistry with two recent Nobel prizes being awarded for developments in this area. These were in 2010 to R. F. Heck, E. Negishi and A. Suzuki with palladium cross coupling reactions and in 2005 to Y. Chauvin, R. H. Grubbs and R. R. Schrock for the development of metathesis reactions. However difficulties have often been encountered in developing novel biocatalytic processes at the industrial scale for the application to C–C bond forming enzymatic reactions due factors that include generating phosphorylated substrates, unfavourable equilibria, low product concentrations and inhibition by substrates and products. This chapter describes some recent developments in C–C lyase chemistry which are now being used in reactions such as the enzymatic Pictet–Spengler reactions and amino acids synthesis using tyrosine phenol lyase. A related enzyme group that could be of interest for synthesis is the tryptophan synthase enzymes that have been also shown to couple a wide range of substituted indoles to serine forming a range of substituted tryptophan derivatives1 (Scheme 10.1) and this reaction nicely complements the halogenase enzymes described in Chapter 11. Decarboxylase enzymes are extremely common in nature and many uses for these are now being found in organic synthesis and two examples are presented which demonstrate the potential use in both chiral synthesis and bulk chemical synthesis.