ENANTIOSELECTIVE INCLUSION COMPLEXATION BY THE CHIRAL HOST AND PHOTOCYCLIZATION REACTION

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.