is illustrated in the below figure. Note that the above product can be protonated from either face with equal probability. The final acid is generated by hydrolysis of the imine. It's worth noting that the alpha keto acid is believed to be formed from a Strecker-like reaction, shown below. From figure 5, we see that the L alpha-methyl amino acids do not directly act as a chiral directing group to generate the normal L amino acid. Researchers hoped that a second molecule of the alpha-methy amino acid could act as a directing group, however they found that the D enantiomer was slightly favored when only L alpha-methyl amino acids were present. The figure below shows how the D enantiomer is favored. When researchers added copper to the reaction, the resulting product was the L enantiomer. Meteors have been found to contain both copper and zinc-justifying the researchers' use of the metal. However, when zinc was used in the same reaction, the L enantiomer was not preferentially formed. Based on computational calculations, the copper forms a square planar complex (shown below) and sterics facilitate protonation to generate the L amino acid. When a slight enantiomeric excess is present, the solubility's of the pure and racemic crystal can be manipulated to generate large ee's of the pure enantiomer. If we define certain solubility's as such: KL= [L] represents the solubility of the pure enantiomer KDL= [D][L] represents the solubility product of the racemic mixture such that [D]= KDL/[L] We can then define the ratio of [L]/[D] = [L]2/KDL When both enantiomers are present, a racemic crystal structure is formed-however it is lower in energy, has a higher melting point, and is less soluble than the enantiomerically pure crystal structure. As a result, when a slight excess of one enantiomer is present, the ee can be amplified by evaporating solvent-causing the racemate to precipitate. Researchers have been able to start with an ee of 1% L, and ultimately end up with 95:5 solution of L: D. The results discussed above (particularly the synchrotron argument) led Breslow to propose that the D amino acids and L sugars could generate life in other parts of the universe. References External links Official biography A Video interview of Professor Breslow 1931 births 2017 deaths People from Rahway, New Jersey Columbia University faculty National Medal of Science laureates Foreign Members of the Royal Society Members of the United