Selfassembly of Molecules in Crystal and Its Application to Selective Synthesis

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Application of the chiral recognition in a host-quest inclusion crystal to optical resolution of the guest compound is successful. The optically active host compounds which were derived from tartaric acid were found to be effective for optical resolution of various guest compounds. Chiral recognition by the optically active diacetylenic alcohol host compound depends delicatelly on its chemical structure. For example, although the optically active diacetylenic alcohol host is not effective for the resolution of an important starting material of prostaglandin synthesis, hydroxycyclopentenone, the diacetylenic alcohol host compound which has p-disubstituted phenyl group between the two acetylenic groups works very well for the resolution.However, alkaloid such as brucine was found to be effective for the resolution of benzhydrol derivatives. Interestingly, the benzhydrol which has a substituent on meta- or para-position of one phenyl group,was resolved efficiently by complexation with bru … More cine. However, the benzhydrol which has an ortho-substituent was not. The structure dependence in the chiral recognition seems to be relating to so called the ortho-effect in organic chemistry in solution.The most interesting finding is the chiral recognition with cinchonidium chloride host. N-Benzoylcinchonidium chloride formed a 1:1 inclusion crystal with 2,2'-dihydroxy-1,1'-binaphthyl. By using the complexation, the latter was resolved very effectively. X-ray crystal structure analysis of the inclusion crystal showed that the hydroxyl group of the binaphthol forms a hydrogen bond network with the chloride anion. Interestingly, the N-benzylcinchonidium chloride was not effective for 10,10'-dihydroxy-9,9'-biphenanthryl which was, however, resolved easily by complexation with N-butylcinchonidium chloride.Some fruitful results were obtained in the study of enantioselective reaction in inclusion crystal. For example, photoirradiation of cyclohexenone and coumarin in their inclusion crystal with an optically active host compound gave optically active dimer. Photoirradiation of an inclusion crystal of acrylanilide with an optically active host gave optically active dihydroquinolinone derivative. The enantioselectivity of these photoreactions in inclusion crystals is almost perfect and optically almost pure enantiomers were obtained. Enantioselective Michael reaction in inclusion crystal was also successful.It was also disclosed that most chiral hosts work as chiral shift reagents. Less