All-trans-9-demethyl-11-methylretinal was synthesized to elucidate the chromophoric interaction between hydrophobic part in retinochrome and 9-methyl substituent of retinal. Photoirradiation of its pigment efficiently gave the 11-cis-isomer in 90% regioselectivity, whereas that of 9-demethylretinochrome provided the 11-cis isomer in 49% selectivity. Structural contribution to regiospecific photoisomerization was proved, in comparison with the other retinochrome analogues, that 9- or 11-methyl substituent is a requisite for highly regioselective photoisomerization, but 13-methyl group is not.
合成了全反式-9-去甲基-11-甲基
视黄醛,以阐明
视黄醛色素中的疏
水部分与
视黄醛的 9-甲基取代基之间的色素相互作用。对其色素进行光照射可有效地得到 11-顺式异构体,其区域选择性为 90%,而对 9-去甲基
视黄醛进行光照射可得到 11-顺式异构体,其区域选择性为 49%。与其他视黄红类似物相比,9-或 11-甲基取代基是高区域选择性光异构化的必要条件,而 13-甲基则不是。