Possible Origins of Diastereomeric Impurities in Synthesized Peptides

21 POSSIBLE ORIGINS OF DIASTEREOMERIC IMPURITIES IN SYNTHESIZED PEPTIDES 

The objective of a synthesis is usually the preparation of an enantiopure peptide. 

However, the product sometimes contains one or more diastereomeric impurities. 

Possible actions and reactions that might have led to the generation of these impurities are as follows  

Use of nonenantiopure amino acid derivatives as starting materials. Notable examples have been serine derivatives that isomerized during tert-butylation and glutamate that isomerized during cyclodehydration to pyro-glutamate. 

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