Oxyma-B, an excellent racemization suppressor for peptide synthesis

Area of Science:

• Organic Chemistry
• Medicinal Chemistry
• Biochemistry

Background:

• Peptide-bond formation is crucial for synthesizing peptide oligomers.
• Carbodiimides are widely used coupling reagents, often with additives like 1-hydroxybenzotriazole (HOBt) and 1-hydroxy-7-azabenzotriazole (HOAt).
• OxymaPure (ethyl 2-cyano-2-(hydroxyimino)acetate) is a modern, safer alternative to benzotriazolic additives.

Purpose of the Study:

• To introduce and evaluate a novel oxime additive, 5-(hydroxyimino)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (Oxyma-B).
• To assess Oxyma-B's solubility, effectiveness in controlling optical purity, and performance in synthesizing challenging peptide sequences.
• To compare Oxyma-B with existing additives like OxymaPure and benzotriazole-based reagents.

Main Methods:

• Synthesis and characterization of the new oxime additive, Oxyma-B.
• Evaluation of Oxyma-B's solubility in common organic solvents (DMF, ACN, THF).
• Assessment of coupling efficiency and optical purity control during the synthesis of various peptide sequences using carbodiimide chemistry with Oxyma-B.

Main Results:

• Oxyma-B demonstrated satisfactory solubility in DMF, ACN, and THF.
• It provided superior control of optical purity compared to OxymaPure and benzotriazole-based reagents for several model peptides.
• Oxyma-B showed excellent performance in synthesizing demanding sequences, including the Aib-enkephalin pentapeptide.
• Oxyma-B is compatible with carbodiimide coupling, unlike some other oxime additives (e.g., HONM).

Conclusions:

• Oxyma-B is a highly effective and versatile additive for peptide synthesis.
• It offers significant advantages in controlling optical purity and coupling efficiency, especially for complex sequences.
• Oxyma-B represents a valuable new tool for synthetic chemists in peptide research and drug discovery.