β-p-Methyl, chloro, cyano and nitrobenzyl-l-aspartates were synthesized, and the respective homopolymers and copolymers of these β-(p-substituted benzyl)-l-aspartates with β-benzyl-l-aspartate were prepared. The introduction of a methyl, chloro, or cyano group into the para position of the aromatic ring in the side chain of poly-β-benzyl-l-aspartate (PBLA) also causes a reversal from the left- to the right-handed in the helical sense of the polypeptide in a chloroform solution, as in the case of the nitro group. The residue of the copolymers where the transition takes place contained: nitro, 20–30; cyano, 40–50; chloro, ca. 50; and methyl group, ca. 70mol.-%. These values may indicate the relative stabilities between the PBLA helix and poly-β-(p-substituted benzyl)-l-aspartate helices. These series of copolymers had no absorption band in the longer wavelength region except for a nitrobenzyl series, which had an absorption band at around 330 mμ. The absence of an absorption band resulted in a normal b0 value. The results suggest that the factors which determine the helical sense of the PBLA helix are not very simple and that the left-handed helix of PBLA is much less stable.
                                    合成了β-对甲基、
氯代、
氰基和硝基苄基-
L-天冬氨酸酯,并制备了这些β-(对取代苄基)-
L-天冬氨酸酯与β-苄基-
L-天冬氨酸酯的均聚物和共聚物。在聚-β-苄基-
L-天冬氨酸ref=https://www.molaid.com/MS_47888 target="_blank">天冬氨酸酯(PB
LA)侧链芳香环的对位引入甲基、
氯基或
氰基,也会导致
多肽在
氯仿溶液中的螺旋方向从左旋逆转为右旋,硝基的情况也是如此。发生转变的共聚物残基中含有:硝基,20-30;
氰基,40-50;
氯基,约 50;甲基,约 70mol.-%。这些数值可能表明了 PB
LA 螺旋与聚-β-(对取代苄基)-
L-天冬氨酸ref=https://www.molaid.com/MS_47888 target="_blank">天冬氨酸螺旋之间的相对稳定性。这些系列共聚物在较长的波长区域没有吸收带,只有硝基苄基系列除外,它在 330 mμ 左右有一个吸收带。没有吸收带导致 b0 值正常。结果表明,决定 PB
LA 螺旋感的因素并不十分简单,PB
LA 的左旋螺旋稳定性要差得多。