Isoserine
Isoserine is a non-proteinogenic α-hydroxy-β-amino acid, and an isomer of serine. Non-proteinogenic amino acids are not part of the genetic code of any known organism. Isoserine has only been produced synthetically. Although it does not occur in natural proteins, such amino acids can be inserted into a protein through post-translational modification.
The first documented synthesis of isoserine in a laboratory setting was by Miyazawa et al., who published their results in 1976.