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Proline organocatalysis is the use of proline as an organocatalyst in organic chemistry. This theme is often considered the starting point for the area of organocatalysis, even though early discoveries went unappreciated. [1] Modifications, such as MacMillan’s catalyst and Jorgensen's catalysts, proceed with excellent stereocontrol. [2]: 5574 [3]
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Proline and its derivatives are often used as asymmetric catalysts in proline organocatalysis reactions. The CBS reduction and proline catalysed aldol condensation are prominent examples. In brewing, proteins rich in proline combine with polyphenols to produce haze (turbidity).
List and Notz also revealed that proline and 5,5-dimethyl thiazolidinium-4-carboxylate appeared to be optimal catalysts within a large group of screened amines. [14] In 2002 the Macmillan group demonstrated a proline-catalyzed aldol reaction between aldehydes. [15] This reaction is unusual because in general aldehydes will self-condense.
In this reaction, naturally occurring chiral proline is the chiral catalyst in an aldol reaction. The starting material is an achiral triketone and it requires just 3% of proline to obtain the reaction product, a ketol in 93% enantiomeric excess. This is the first example of an amino acid-catalyzed asymmetric aldol reaction. [16] [17]
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Arginine and proline metabolism is one of the central pathways for the biosynthesis of the amino acids arginine and proline from glutamate. The pathways linking arginine, glutamate, and proline are bidirectional. Thus, the net utilization or production of these amino acids is highly dependent on cell type and developmental stage.
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