Amino acids are molecules that are present in all living organisms. These high-value compounds are the building blocks used for the synthesis of peptides and proteins, and many of them are essential nutrients and energy metabolites. In addition to that, they are commonly used in catalysis as asymmetric ligands, as metal scavengers, or as scaffolds for the synthesis of biodegradable surfactants. Furthermore, the fact that they contain an amino group and a carboxylic acid moiety in their structure, both tending to form hydrogen bonds with their surroundings, makes them of crucial importance in medicinal chemistry.Applying structural modifications on this family of compounds may alter their chemical properties, offering new possibilities to enhance their performance. Unfortunately, due to their high polarity and low solubility in organic solvents, the modification of readily available amino acids is very difficult. 

Synthetic methods are dependent on installing protecting groups or introducing derivatizations along the process. This increases the number of synthetic steps needed to obtain the desired products, generating large amounts of waste and employing very large amounts of organic solvents. 

In this article, we present an alternative approach that consists of the direct N-functionalization of unprotected amino acids using readily accessible alcohols as alkylating agents. The reaction is catalyzed by a newly designed iridium complex. This methodology yields the modified amino acids with excellent selectivity, in quantitative yields and in a single synthetic step. Thus, without the need of installing and removing protecting groups. Furthermore, water is the only by-product of the reaction. As the reactions are quantitative, the products are purified by a simple filtration. This also saves the use of organic solvents that are needed for extraction and purification process.
The sustainability of the method was further improved by catalyst and solvent recycling studies, which showed that the catalyst could be reused for several runs, and the solvent can be recovered and reused without affecting the efficiency.

This new catalytic system represents a major outbreak in the field and could be applied for the synthesis of more than 100 compounds, including the synthesis of biodegradable surfactants, and of two N-modified peptides. This is presented as a green alternative to get access to high-value compounds with potential applications that are to be investigated.

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