Chirality in amino acids

Barlow S, Raval R (2008) Nanoscale insights in the creation and transfer of chirality in amino acid monolayers at defined metal surfaces. Curr Opin Colloid Inter Sci 13 65... 

Asymmetric hydrogenation of either a carbonyl or an imino group to a hydroxyl group or an amino group has frequently been employed for the introduction of chirality in amino acid syntheses. Corey s catecolborane-oxazaborolidine protocol enables transformation of difluoromethyl ketone 1 into alcohol 2 with excellent enantioselectivity. The reaction of diastereoselective amination of a-hydroxyaldehyde 3 with A,A-diallylamine and 2-furyl-boronic acid provides furyl amino alcohol 4 in good chemical yield along with excellent diastereoselectivity. This protocol is applicable for the preparation of amino acids and amino alcohols with a trifluoromethyl group by the combination of /V,/V-diallyl or N,N-dibenzyl amine and aromatic, heteroaromatic and alkenyl boronic acids [7]. The usual chemical transformations as shown in steps 5 to 8 in Scheme 9.1 lead to (2S,3R) difluorothreonine 5 [8]. 

While the answer to this question is uncertain, there have been some interesting developments in this area. It has been shown that life (as it exists today anyway) cannot arise from a racemic mixture of amino acids because the presence of chiral centers in many biomolecules is crucial for biological function. The self-replication of DNA relies on the presence of chiral centers and without a shared chirality, the error rate in DNA replication would cause severe problems for many longer-lived plants and animals. One hypothesis for the origin of chirality is that molecules from outer space reached Earth with a net chirality already present. Another is that the net chirality in amino acids was established on Earth in a very short period of time. It s a pretty interesting thing to think about, and this topic is a subject of ongoing research and debate. 

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