Chemical and Stereochemical Nature of Amino Acids

JP Moss. Basic terminology of stereochemistry. Pure Appl. Chem. 68, 2193, 1996. 

FIGURE 1.1 Chemical and stereochemical nature of amino acids. Substituents in (a) and (b) are on opposite sides of the plane N-Ca-C, the bold bond being above the plane. Interchange of any two substituents in (a) changes the configuration. For the Cahn-Ingold-Prelog system of nomenclature, the order of preference NH2 COOH R2 relative to H is anticlockwise in (a) = (S) and clockwise in (c) = (R). 

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