Allothreonine metal complexes

Decomposition of the copper complex with HjS in acid leads to allothreonine and (in about 2-fold excess) threonine. Following the pioneering work of Akabori et this reaction has been extended to a variety of metals and aldehydes and to complexes such as A- and A-Co(en)2gly with intriguing stereoselectivity behavior (optically-active allothreonine and threonine products). ... 

Threonine and allothreonine are thermally unstable amino acids. The same is true for the simplest hydroxy amino add, (S)-serine (39). High levels of this amino add have however been reported from certain petroleum brine waters and its preservation may be due to the formation of stable chelates. Ahrens has suggested that metal-amino acid chelates may be important in the sedimentary cycle, and the uptake of certain metals in sediments, particularly in binding of metal-amino acid chelates to clays, has been proposed as a possible mechanism for the incorporation of metal ions in carbonaceous materials. Similar complexes are thought to contribute to the stabilization of amino acids in coals, lignites and peats, but, as has been outlined in a previous section, many other ligands are also present in these media, and their relative importance is difScult to assess. Much of this work is unfortunately of a speculative nature since no well-characterized complex of an amino acid has been isolated from a geological source, as far as the author is aware. 

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