S. Akutsu et al., ENANTIOSELECTIVE INCLUSION COMPLEXATION BY THE CHIRAL HOST AND PHOTOCYCLIZATION REACTION, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 276, 1996, pp. 87-93
The chiral host 1 derived from tartaric acid formed the 1:1 inclusion
complex with 2 by incorporating one of the enantiomers of 2 into the c
omplex crystal. The irradiation of 2 gave optically pure product 3. Th
e host 1 formed the 2:1 inclusion complex with the prochiral guest 4.
The irradiation of this complex gave optically pure 5. In order to elu
cidate the enantioselective inclusion complexation and the stereospeci
fic control of the photocyclization reaction by host 1, the X-ray crys
tallographic study of 1 . 2, 1 . 4 and 5 have been undertaken. All str
uctures were solved by direct methods and refined by full-matrix least
-squares refinement to give final R values of 0.055 for 1 . 2, 0.040 f
or 1 . 4 and 0.049 for 5. Each host molecule has one O-H---O intramole
cular hydrogen bond and the same conformation. The enantioselective co
mplexation in 1 . 2 will be attained by the specific host-guest intera
ctions observed in the complex crystal, allowing an easy and straightf
orward method to prepare the optically pure 3 with the determination o
f the absolute configuration of 3 by reference to the known chirality
of 1. The overall structure of the 2:1 inclusion complex of 1 . 4 clea
rly shows the stereochemical control, which forms the optically pure 5
from the prochiral 4. The absolute configuration of 5 was deduced fro
m the host-guest relative orientation in the 1 . 4 complex crystal and
the known absolute configuration of 1.