Explanation:
Amino acids are the organic compounds which contains both amine as well as carboxyl functional groups, with a side chain along to the molecule which is specific to each amino acid.
Threonine is a naturally occurring amino acid which has two stereogenic centers. The possible stereoisomers of theronine is 4. The naturally occurring amino acid has the 2S, 3R configuration at its two stereogenic centers.
The structure is shown in image below.
