Highly Z-Selective Horner-Wadsworth-Emmons Olefination Using Modified Still-Gennari-Type Reagents.

In this report, new, easily accessible reagents for highly Z-selective HWE reactions are presented. Alkyl di-(1,1,1,3,3,3-hexafluoroisopropyl)phosphonoacetates, structurally similar to Still-Gennari type reagents, were tested in HWE reactions with a series of various aldehydes. Very good Z-selectivity (up to a 98:2 Z:E ratio) was achieved in most cases along with high yields. Application of the new reagents may be a valuable, practical alternative to the well-established Still-Gennari or Ando Z-selective carbonyl group olefination protocols.

Preparative scale application of Mucor circinelloides ene-reductase and alcohol dehydrogenase activity for the asymmetric bioreduction of α,ß-unsaturated γ-ketophosphonates.

The fungus Mucor circinelloides exhibits high potential for green chemistry and technological applications. Recently M. circinelloides, which so far was considered mainly as a platform for biodiesel production, was found to exhibit high ene-reductase activity. In our current research we applied this promising microorganism to the biotransformation of a series of α,ß-unsaturated γ-ketophosphonates. The biotransformations were conducted using cheap corn steep liquor or minimal media. The products were obtained with excellent enantiomeric purity (>99% ee in most cases) and in good isolated yields, highlighting the great potential of this microorganism for asymmetric synthesis. Moreover, the products obtained may be further applied as chiral building blocks for the synthesis of biologically active compounds, such as glutamic acid or fosmidomycin derivatives.

The first enzyme-promoted addition of nitromethane to imines (aza-Henry reaction).

Enzyme catalytic promiscuity is the ability of a single enzyme active site to catalyze several chemical transformations, among them those which are different from natural. We have attempted to use this feature of enzymes in the nucleophilic addition of nitromethane to aldimines (the aza-Henry reaction) whose chemically catalyzed version leads to synthetically useful ß-nitroamines. We succeded in obtaining for the first time the desired products in the yields up to 81%. The most efficient proved lipase TL (from Pseudomonas stutzeri) and oxynitrilase from Arabidopsis thaliana. However, all the reactions investigated were non-stereoselective.