Tomatoes get defensive

Efficient synthesis of methyl lycotetraoside, the tetrasaccharide constituent of the tomato defence glycoalkaloid a-tomatine  

Nigel A. Jones, Sergey A. Nepogodiev and Robert A. Field       

Complex natural products called saponins are produced by plants as a response to attack by pathogenic fungi. Saponins specifically disrupt the cell membrane of invading microorganisms, resulting in death of the fungus. In response, fungi produce a variety of enzymes that modify saponins, resulting in their inactivation. Little is currently known about this 'chemical conversation' between plants and fungi. Saponins tend to be produced in nature in very low quantities; they are very difficult to extract and purify from natural sources. Hence the availability of pure materials from chemical synthesis is crucial to enabling key studies to understand the ecological relationship between plants and fungi.    

Sergey Nepogodievand colleagues at the University of East Anglia, UK provide a fast and flexible synthetic route to the complex carbohydrate structures found in the saponins produced by tomatoes as part of their response to attack by fungi. 

The challenge is to develop flexible methods that allow late-stage decisions about which sugars to incorporate and where. The need to stitch together multiple sugars residues in linear or branched arrangements pushes the limits of current chemical methods. The saponin challenge presents opportunities for development of highly selective one-pot, multiple-coupling strategies, and for the application of solid-phase and/or automated technologies