A series of linear peptides with the general formula H‐Glu(R1)‐Glu(R2)‐OH was subjected to cyclization under standard conditions. Formation of respective 2,5‐diketopiperazines was accompanied by transformation of the N‐terminal Glu(R1) to… Click to show full abstract
A series of linear peptides with the general formula H‐Glu(R1)‐Glu(R2)‐OH was subjected to cyclization under standard conditions. Formation of respective 2,5‐diketopiperazines was accompanied by transformation of the N‐terminal Glu(R1) to pyroglutamic acid residue. Even in the case R1 is an amino acid residue attached to the N‐terminal γ‐carboxyl group, lactamization leads to its elimination. The observed reaction has not been reported so far in the literature. Correspondingly, an alternative route to Glu(R1)‐Glu(R2)‐containing 2,5‐diketopiperazines was applied to improve the overall yields.
               
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