First Isolation and Stereochemistry of Optically Active Telluroxides

Optically active telluroxides 1 and 2 were isolated for the first time by means of medium-pressure liquid chromatography using an optically active column. Absolute configuration of the telluroxides (+)-1 and (+)-2 was determined to be R based on their specific rotations and circular dichroism spectra. The configurational lability and mechanism for racemization via an achiral hydrate were clarified by kinetic study and isotope tracer experiment.     

Synthesis of Optically Active Tetraoxa‐Cage Compounds by Chemical Resolution

The first synthesis of optically active tetraoxa‐cage compounds has been accomplished by using (‐)‐camphanic chloride as a resolving reagent in a short sequence. The synthesis of the tetraoxa‐cages with different functional groups on the side chain was also demonstrated.     

Synthesis of Rigid and Optically Active Bis(binaphthyl) Cyclic Compounds

Optically active cyclic bis(binaphthyl)s (4a–d), which are composed of aromatics, ethers, and ketonic carbonyls, were synthesized through a two‐step nucleophilic aromatic substitution reaction. Bis(binaphthyl) cyclic compounds (4a and 4b) were obtained in moderate yields when difluoride 3a and 3b were employed. On the other hand, bis(binaphthyl)s 4c and 4d were scarcely obtained when 3c and 3d were employed.     

Exploring Clathrate Formation with an Optically Resolved Host. X-Ray Crystal Structure of the Inclusion Compound between (11S,12S)-(-)-9,10-Dihydro-9,10-ethanoanthracene-11,12-dicarboxylic Acid and n-Hexane (2 : 1)

The crystal structure of the inclusion compound formed between (11S,12S)-(-)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid, (1), and n-hexane (2:1) has been studied by X-ray diffraction. It crystallizes in the tetragonal space group P41 and represents a less common type of inclusion compound, which has helical and chiral structural elements. Helical chains, formed by hydrogen-bonded host molecules, wind around the 21 screw axes and encircle the guest molecules. Crystal data: a=b=17.478(1); c=12.021(1)Å, Z=4 host–guest 2:1 units, R=0.043, Rw=0.061 for 2225 observations with I > 3 (I). The general shape and conformational flexibility of 1 with respect to the requirements of inclusion formation and crystal packing are discussed.     

Crystalline Inclusion Compounds Derived from Derivatives of Mandelic Acid. Host Synthesis, Inclusion Formation, and X-Ray Structures of a Free Host Compound and of DMSO Inclusion Complexes in Both Racemic and Optically Resolved Forms

New chiral host compounds based on mandelic acid derivatives having methyl (6a, b and 8a, b) or bromo substituents (7a, b) attached to the phenyl ring of mandelic acid and involving additional aromatic groups were synthesized. The inclusion properties of both the racemic and the optically resolved host species are reported, including solvent co-crystallization as well as chiroselective and vapour sorptive inclusion. The structures of the free racemic host compound 6b and of the DMSO inclusion compounds of optically resolved and racemic 8 (8a and 8b, respectively) have been determined by X-ray analysis. Enantiomeric pairs of molecules in 6b form centro-symmetric dimers by mutual hydrogen bonding of one hydroxyl group while the other is involved in O-–H ... interactions. The guest molecules in the DMSO complexes of 8a and 8b are bound via hydrogen bonds to two host molecules related by translation along crystallographic axes. Parallels to previous hosts of this type are drawn.