Thursday, August 25, 2011

New building blocks for synthesis of complex molecules

Chemists at the University of Illinois have developed a way of fitting chemical pieces together to more efficiently build complex molecules, beginning with a powerful and promising antioxidant.

A standard synthesis technique called iterative cross-coupling (ICC) uses simple, stable chemical building blocks sequentially joined in a repetitive reaction. With more than 75 of the building blocks available commercially, pharmaceutical companies and other laboratories use ICC to create complex small molecules that could have medicinal properties.

The University of Illinois chemists have now developed a variant of ICC called reverse-polarity ICC that allows them to better match the target molecules’ electronic structure. The reversal in polarity enables a whole new class of building blocks, so researchers can synthesize molecules more efficiently and even construct molecules that standard ICC cannot.

Creating a more powerful antioxidant

The chemists used the new method to make synechoxanthin, a molecule first isolated from bacteria in 2008 that shows great promise as an antioxidant.  Studies suggest that synechoxanthin allows the bacteria that produce it to live and thrive in highly oxidative environments.

Studies on the activity of synechoxanthin have been limited by the difficulty of extracting the molecule from bacterial cultures. The chemists successfully synthesized it from just three types of readily available, highly stable, non-toxic building blocks. Thanks to the ease of ICC, they can produce relatively large quantities of synechoxanthin for study as well as derivatives to test against the natural product.

“Because this building-block-based design is inherently flexible, once we’ve made the natural product, we can make any derivative we want simply by swapping in one different building block, and then using the reverse-polarity ICC to snap them together,” said professor Martin Burke. “That’s where synthesis is so powerful. Oftentimes, the cleanest experiment will require a molecule that doesn’t exist, unless you can piece it together.”

The researchers can also use blocks that have been tagged with a fluorescent or radioactive dye to make it easier to study a particular molecule and its activity.


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