Photocyclization of photoswitches with high enantioselectivity in human serum albumin in an artificial environment.

Three photochromic bisthienylethenes exhibited 56 to >99% enantiomeric excess in photochemical ring closure upon UV irradiation when incorporated in human serum albumin dissolved in 15% acetonitrile-phosphate buffer solution and incubated for 24 h at -4 °C. The absolute stereochemistry of the major enantiomers of two bisthienylethenes has been determined by their chemical transformations.