Pretransitional layer contraction at the chiral smectic A-to-chiral smectic C phase transition of a chiral nitroxide radical.

We have designed and synthesized a new chiral paramagnetic liquid crystalline compound with a nitroxide radical moiety showing chiral smectic A (SmA*) and C (SmC*) phases. This compound shows pretransitional layer contraction prior to the SmA*-to-SmC* phase transition in the cooling run. Electron paramagnetic resonance spectroscopy, X-ray diffraction analysis, and polarized optical microscopy reveal that a temperature-dependent conformational change is responsible for the pretransitional layer contraction.

New resolution technologies controlled by chiral discrimination mechanisms.

It is well known that optical resolution via crystallization is still a useful and practicalmethod for obtaining enantiomerically pure compounds for both laboratory experiment and industrial production,although it is a classical technique discovered nearly 160 years ago. In particular, diastereomericsalt formation using a resolving agent (diastereomer method) has been well applied in various fieldssuch as the pharmaceutical, agrochemical, and liquid crystal industries. Despite these affluent reportedand patented examples, unfortunately no concrete theory to determine an optimum resolution condition hasbeen devised, and only empirical procedures seem to provide a unique path in process development. Inthis chapter, three novel approaches for optical resolution via diastereomeric salt formation are presented:(1) chiral purity improvement by crystal habit modification with a tailored chiral additive; (2) a newapproach for finding a suitable resolving agent based on the space filler concept; and (3) chiralitycontrol by dielectrically controlled resolution.

Optical resolution of 5-alkyl-delta-valerolactones and synthesis of optically active 5-fluoroalkanols.

Optical resolutions of 5-alkyl-delta-valerolactones were carried out by derivatization to the diastereomeric amides, in which (R)-(+)-1-(1-naphthyl)ethylamine or (S)-(-)-1-phenylethylamine were used as resolving agents. Optically active 5-fluoroalkanols, useful intermediates for fluorinated ferroelectric liquid crystals, were derived from the resolved lactones in four steps without racemization.

Crystal and solution structures of photochromic spirobenzothiopyran. First full characterization of the meta-stable colored species.

Full elucidation for stable, colorless, and meta-stable colored structures of a new spirobenzothiopyran has been achieved both in the solid state and in a solution. 1',3',3'-Trimethyl-6-nitrospiro[(2H)-1-benzothiopyran-2,2'-indoline] with an ester group as a substituent at the 8-position of 1-sp shows photochromism. The blue-green colored species resulted from UV irradiation (365 nm) in one minute and spontaneously bleaches within one minute in acetone and methanol at 27 degrees C. UV exposure (365 nm) of 1-sp in methanol for 3 h at room temperature results in the growth of deep blue needlelike single crystals of the open form of spirobenzothiopyran, photomerocyanine 1-pmc, whose structures in the solid state and in solution were obtained unambiguously. The X-ray structural analysis of 1-pmc revealed the molecular structure of the zwitterionic photomerocyanine with s-trans,s-trans conformation. 1-pmc is soluble to polar solvents and thermally returns to 1-sp. In the DMSO solution, 1-pmc is found to return slowly to 1-sp (1-pmc gave only 18% of 1-sp for 30 min at 22 degrees C). The detailed NMR studies in DMSO-d(6) including COSY and NOE techniques as well as isotope labeling of the compound showed the structure with s-trans,s-cis conformation in a solution.