Studies on optically Active Amino Acids. XVIII. Studies on α-Methyl-α-amino Acids. XIV. Several Optical Properties of α-Methyl-α-amino Acids

Abstract

Several optical properties of α-methyl-α-amino acids (I), whose absolute configurations have already been established in our laboratory, were investigated, and compared with those of protein derived L-amino acids (II). On N-dithiocarbethoxy α-methyl-α-amino acids (III) with the same absolute configuration, the opposite ORDand CD curves were observed in the same solvent. Moreover, changes of direction of ORD and CD curves were not found by changing the solvent. These results were clearly different from those obtained on N-dithiocarbethoxy L-amino acids (IV). Examinations of Clough-Lutz-Jirgensons rule on I do not exhibit good relationships between absolute configurations and their positive values of [M]HClD-[M]H2OD. This reuslt was also different from that reported on II. However, hydantoin derivatives of I with (S)-configuration, showed large negative rotations with one exception, the same as those of II. From these studies, it has become apparent that the hydantoin rule is most useful for the assignment of absolute configuration of I.