Optical rotatory dispersion. Part XXXVIII. Azomethines. Part III. Configurational assignment in the α-amino-acid series using N-alkylidene derivatives

Abstract

The preparation and properties of further N-neopentylidene derivatives of α-amino-acid esters are described. The β-hydroxyesters are anomalous in that they react with pivaldehyde to give oxazolidines which do not show the pronounced Cotton effects in the 250 mµ region found for the azomethine derivatives.The condensation of pivaldehyde, isobutyraldehyde, and other carbonyl compounds with α-amino-acid anions in alcoholic solution has been examined by rotatory dispersion methods. With certain exceptions (proline, β-hydroxy acids, histidine, and tryptophan) pronounced Cotton effects have been observed with the first extremum at ∼245 mµ. Since the azomethine derivatives of L-α-amino-acids give negative Cotton effects and the derivatives of D-α-amino-acids give positive ones, these observations provide a simple method for assigning configuration in the α-amino-acid series.