CHAMPAIGN, Ill. - The synthesis of both left- and right-handed versions (enantiomers) of alpha-, beta- and gamma- (aryl) amino acids is the latest application of a new chemical methodology developed by a chemist at the University of Illinois.

"The importance of both natural and unnatural amino acids to medicinal and biological chemistry has made these compounds a focal point for chemical synthesis," said Peter Beak, a U. of I. professor of chemistry. "We have demonstrated that our methodology will produce both enantiomers of three types of aryl amino acids more efficiently and more conveniently than conventional techniques."

Amino acids ­ like many organic molecules ­ exhibit a particular "handedness," or chirality. The two resulting structures, called enantiomers, are analogous to a pair of hands: They form nonsuperimposable mirror images of each other. The reactions of chiral compounds are highly structure dependent, just as the right hand of one person requires the right hand of another to perform a handshake. Thus, the correct chirality must be built into a synthesized biomolecule.

"Our chemistry begins with a molecule that is superimposable on its mirror image, and converts it into an aryl amino acid that is nonsuperimposable on its mirror image," Beak said. "Our yields are high, depending upon the reagent being used and the type of amino acid being produced."

Beak's methodology, developed in collaboration with Yong Sun Park, a postdoctoral research associate, uses a process of transient molecular bonding called chiral ligand binding. In this synthetic approach, an auxiliary molecule ­ the ligand ­ binds to a lithium ion, which is associated with an amine derivative present in the solution, to make a complex. Because the ligand is chiral, it also imparts the correct "handedness" to subsequent reactions.

"The key to our technique is the association between the lithium ion and the chiral ligand in a critic
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Contact: James E. Kloeppel, Physical Sciences Editor
kloeppel@uiuc.edu
217-333-5802
University of Illinois at Urbana-Champaign
2-May-1997