Bovine serum albumin-mediated enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate.
Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxyalate (AC) was performed at 25 degrees C in aqueous buffer solution (pH 7) in the presence of bovine-serum albumin (BSA) to afford four [4 + 4] cyclodimers, i.e., anti- and syn-head-to-tail (HT) (1 and 2) and anti- and syn-head-to-head (HH) dimers (3 and 4), of which only 2 and 3 are chiral. We found that (1) BSA possesses four sets of binding sites for AC of different affinities, stoichiometries, and chiral environment for photoreaction, which bind 1, 3, 2, and 3 AC molecules with binding constants of 5.3 x 107, 1.3 x 105, 1.4 x 104, and 3.0 x 103 M-1, respectively, (2) the regioselectivity of photodimerization is switched from HT to HH by adding BSA (the HH/HT ratio varies from 0.28 to 4.3), (3) BSA-mediated photodimerization of AC affords optically active products 2 and 3 of up to 29% and 41% ee, respectively. It is emphasized that the selective excitation of bound substrate, utilizing the spectral shift upon complexation with BSA, is not a prerequisite for efficient photochirogenesis using biomolecules.
Wada
Takehiko
T
Department of Molecular Chemistry, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan.
Nishijima
Masaki
M
Fujisawa
Tai
T
Sugahara
Norimitsu
N
Mori
Tadashi
T
Nakamura
Asao
A
Inoue
Yoshihisa
Y
D000818:Animals; D000873:Anthracenes / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D002417:Cattle; D002942:Circular Dichroism; D003500:Cyclization; D019281:Dimerization; D010777:Photochemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013237:Stereoisomerism
C476641:2-anthracenecarboxylate; D000873:Anthracenes; D002264:Carboxylic Acids; D012710:Serum Albumin, Bovine