Amino Acid Derivatives by MCRs

SCHEME 6.54 Asymmetric synthesis of, , 5-dihydropyrroles 370 in water and proposed mechanism. 

There is no doubt about the importance of the development of efficient method for the synthesis of amino acids, a kind of molecules of great value. In this sense, MCRs provide 

Kazmaier and coworkers have observed the formation of eight-membered rings or linear side products when ammonia is used as amine partner in the aforementioned reaction [122]. The desired amino acids are obtained as minor product or only in traces. These side reactions can be avoided when nonnucleophilic alcohols are used like trifluoroethanol sterically demanding aldehydes, like pivalaldehyde and sterically demanding carboxylic acids. 

HjN COOH H2N COOH H2N COOH H2N H2N COOH H2N COOH H2N COOH 

SCHEME 6,56 Large-scale synthesis of unnatural amino acids 380 using an Ugi reaction. 

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