... as polar. Together with serine, threonine is one of two proteinogenic amino acids bearing an alcohol group ... as phosphothreonine.Threonine is one of two amino acids out of the twenty with two chiral centers, threonine ... 3R). However, the name L-threonine is used for one single enantiomer, (2S,3R)-2-amino-3-hydroxybutanoic ... nature, is called L-allo-threonine. The two stereoisomers (2R,3S)- and (2R,3R)-2 ...