Buffer-Mediated Catalyst-Free Strecker Reaction Toward Enzymatic Implementation.

Area of Science:

• Organic Chemistry
• Green Chemistry
• Biocatalysis

Background:

• The Strecker reaction is a fundamental method for synthesizing α-aminonitriles.
• Traditional Strecker reactions often require harsh conditions, catalysts, or extensive purification.
• Developing environmentally friendly and efficient synthetic routes is crucial for sustainable chemistry.

Purpose of the Study:

• To develop a catalyst-free Strecker reaction in aqueous buffer.
• To optimize reaction conditions for enhanced yield and efficiency.
• To explore the potential of enzymes in accelerating the reaction.

Main Methods:

• Systematic investigation of catalyst-free Strecker reaction in aqueous buffer.
• Optimization of pH and buffer concentration.
• Evaluation of different cyanide sources (potassium cyanide, acetone cyanohydrin).
• Exploration of mixed solvent systems (buffer-methyl tert-butyl ether).
• Inclusion of hydroxynitrile lyases (AtHNL, HbHNL) to assess enzymatic acceleration.

Main Results:

• Achieved high yields (up to 97%) of α-aminonitriles without chromatography.
• Demonstrated broad substrate scope with various aldehydes, ketones, and amines.
• Identified low pH and high buffer concentration as key optimization parameters.
• Established acetone cyanohydrin as a safer and effective cyanide source.
• Observed accelerated reaction rates upon addition of hydroxynitrile lyases.

Conclusions:

• The developed method offers an efficient and green alternative for α-aminonitrile synthesis.
• The reaction is suitable for producing key intermediates for natural and unnatural amino acids.
• Hydroxynitrile lyases show potential for undiscovered reactivity in catalyzing Strecker-type reactions.