Manifestations of Stereoisomerism

Stereoisomerism manifests itself in various forms, such as those related to enantiomers, epimers, diastereoisomers, meso compounds, geometrical isomers, etc. Generally speaking, the consequences of stereoisomerism for the disposition and biological action of xenobiotics in living... 

Threonine (a-amino-d-hydroxybutyric acid) is the next higher homolog to serine. Its name points to the relationship with the sugar threose. Threonine has two asymmetric centers (cf. Chapt. 1-4) manifested by four stereoisomeric forms of which two are always mirror images of the other two namely d- and L-threonine and D- and L-allothreonine. Threonine was discovered in an interesting manner it was identified as a necessary supplementary factor of a synthetic diet mixture (Rose 1935) and thus became the first amino acid to be recognized as indispensable. 

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