Enantioselective Photochromism of Diarylethenes in Human Serum Albumin

Making light work of chromism: Enantioselective photochromic ring-closing reactions of three bisthienylethene compounds possessing either no or two hydroxy groups were carried out in the hydrophobic pockets of human serum albumin (HSA) in aqueous media. When 10 equivalents of HSA were used, 1,2-bis(5-hydroxymethyl-2-methyl-3-thienyl)hexafluorocyclopentene predominantly produced the S,S closed form (see scheme; O=open, C=closed), in 63 % ee at RT and 71 % ee at −4 °C upon irradiation with 313 nm light.