New catalyst selectively generates amino acid precursors from cyanide at room temperature

Oct 10, 2012
The self-supporting catalyst (top) is covered with tiny chiral pockets, within which simple starting materials (bottom, left) are converted into chiral amino acid precursors (bottom, right). Credit: 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Cyanide exposure can be lethal, but with careful handling, the molecule can be a very useful chemical building block. For example, from cyanide chemists can make life-essential amino acids that are in great demand as food additives and components in pharmaceutical production. The key step in this process is called the asymmetric Strecker reaction. Until now, this reaction has needed complex and costly catalysts, restricting its use to small-scale laboratory research. A new Strecker catalyst more amenable to scale-up  is now available, thanks to Abdul Seayad, Balamurugan Ramalingam and their co-workers at the A*STAR Institute of Chemical and Engineering Sciences in Singapore. The catalyst also offers a safer way to handle the cyanide.

Seayad and Ramalingam made their Strecker from an inexpensive material based on titanium. It is called the self-supported chiral titanium cluster (SCTC). When warmed in the presence of water, the SCTC precursor assembles into robust solid clusters (see image). The key to its performance in the Strecker reaction is that the surface of each cluster is covered in tiny asymmetric "chiral pockets", says Seayad. The reactions take place in these pockets, generating molecules that are a trivial chemical step away from amino acids.

Amino acids are chiral: they can exist in either of two mirror-image forms called enantiomers. For many applications—such as —chemists need a pure supply of only one . Seayad and Ramalingam found that SCTC's chiral pockets very selectively produce one enantiomer over the other, with a purity—or 'enantiomeric excess'—of up to 99%. Unlike previous catalysts, which required temperatures as low as -30 °C to operate effectively, the researchers achieved this at room temperature.

Stability is a further advantage of SCTC. The catalyst is impervious to air or moisture, and remains stable to 300 °C, making it well suited to use in a continuous flow reactor. The researchers could pack the catalyst into a cartridge and pump through the cyanide and other starting materials, generating amino acids in a steady stream. Safety is another key advantage, says Ramalingam. "Since only a limited amount of cyanide is present at the reaction zone at any point in time, any unforeseen situation can be easily handled," he explains.

So far, the researchers have used an expensive reagent called TMSCN as their cyanide source. They are currently researching ways to generate SCTC in situ from inexpensive salts. "We will also evaluate the feasibility of up-scaling the reaction under flow conditions," Seayad says.

Explore further: Recycling industrial waste water: Scientists discover a new method of producing hydrogen

More information: Seayad, A. M., Ramalingam, B., Chai, C. L. L., Li, C., Garland, M. V. & Yoshinaga, K. Self-supported chiral titanium cluster (SCTC) as a robust catalyst for the asymmetric cyanation of imines under batch and continuous flow at room temperature. Chemistry – A European Journal 18, 5693–5700 (2012). onlinelibrary.wiley.com/doi/10.1002/chem.201200528/abstract

add to favorites email to friend print save as pdf

Related Stories

Organic chemistry: Amino acids made easy

May 04, 2011

Amino acids are the building blocks of proteins. There are 22 different amino acids and they can combine in a myriad ways to form a vast array of proteins. All amino acids except glycine are chiral molecules, ...

Taming the molecule's Dr. Jekyll and Mr. Hyde

Jun 14, 2011

Many organic molecules are non-superimposable with their mirror image. The two forms of such a molecule are called enantiomers and can have different properties in biological systems. The problem is to control which enantiomer ...

High-yield selective synthesis of specific molecules

Jul 06, 2012

Organic chemists seek synthesis reactions that produce high yields of very pure products. European researchers have developed novel synthetic reactions for a class of compounds particularly relevant to potential ...

Plants and caterpillars make the same cyanide

Apr 13, 2011

(PhysOrg.com) -- With an amazing example of convergent evolution, Niels Bjerg Jensen of the University of Copenhagen published a report in Nature Communications discussing the bird's-foot trefoil plant and th ...

Efficient catalysis on chiral surfaces

Aug 24, 2012

(Phys.org)—Practice is when everything works but nobody knows why. This light-hearted saying can equally be applied to chemical processes. "The process of so-called heterogeneous asymmetric catalysis is ...

Recommended for you

A greener source of polyester—cork trees

Apr 16, 2014

On the scale of earth-friendly materials, you'd be hard pressed to find two that are farther apart than polyester (not at all) and cork (very). In an unexpected twist, however, scientists are figuring out ...

User comments : 0

More news stories

LinkedIn membership hits 300 million

The career-focused social network LinkedIn announced Friday it has 300 million members, with more than half the total outside the United States.

Magnitude-7.2 earthquake shakes Mexican capital

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.