Although carbohydrates were previously thought of as little more than an energy source, it is now recognised that they play a key role in many biochemical processes including intercellular recognition, immune function, fertilisation and certain types of cancer. From a synthetic viewpoint, the structural complexity that makes carbohydrates important in so many biological processes poses significant challenges. Unlike oligonucleotides and peptides, carbohydrates can form branched as well as linear structures, and there are a staggering number of ways in which monosaccharides can be combined. Increasingly powerful and versatile methods have been developed to allow the synthesis of pure oligosaccharides in the laboratory, but the process requires regioselective protection of hydroxyl groups as well as stereoselective assembly of glycosidic linkages and is technically difficult and very time consuming. Speaking at the annual meeting of the American Chemical Society in Salt Lake City, Dr Peter H Seeberger has described the development of a fully automated carbohydrate synthesiser that should make complex carbohydrates more accessible. A simple cleavage, deprotection and purification protocol provides rapid access to naturally occurring and synthetic oligosaccharides and is suitable for use by non-experts.
One application that Seeberger’s group have been addressing with the new technology is the development of a vaccine against malaria. Fatalities caused by the malaria parasite, Plasmodium falciparum, are thought to result, at least in part, from a reaction to the malaria toxin, glycosylphosphatidylinositol (GPI). Anti-GPI vaccination was found to protect against fatality in mice and clinical trials of an anti-toxin vaccine to protect against the inflammation and anaemia associated with malarial infection are scheduled for 2010 in Mozambique and Tanzania. Seeberger also believes that carbohydrate-based vaccines could be used against other serious infectious diseases, including antibiotic-resistant infections and HIV.