11-Methyl-9-demethylretinal and 11-methyl-9,13-didemethylretinal. Effect of altered methyl substitution pattern on polyene conformation, photoisomerization and formation of visual pigment analogs
作者:Leticia U Colmenares、Robert S.H Liu
DOI:10.1016/s0040-4020(01)80897-8
日期:——
Altered methylsubstitution pattern in 11-methyl-9-demethylretinal (1) and 11-methyl-9,13-didemethylretinal (2) resulted in changed polyene conformation, regioselectivity of photoisomerization, uv/vis characteristics and reactivity toward bovine opsin. That the 11-cis isomer of 1 and 9-cis isomer of 2 gave visual pigment analogs (λmax 475 and 459 nm respectively) while the 11-cis isomer of 2 did not
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.