Roles of sigmatropic migration of a benzoyl group and intermolecular hydrogen bonding between a tropone carbonyl and an NH group on the mesomorphic properties of 2-(4-alkoxybenzoyloxy)-5-alkylaminotropones and 5-alkoxy-2-(4-alkylaminobenzoyloxy)tropo

The mesomorphic properties of 2-(4-alkoxybenzoyloxy)-5-alkylaminotropones and 5-alkoxy-2-(4-alkylaminobenzoyloxy)tropones are discussed on the basis of results obtained by X-ray crystallographic and X-ray diffraction studies, as well as temperature-dependent FTIR spectral measurements. The X-ray crystallographic analysis of 2-(4-dodecylaminobenzoyloxy)-5-tetradecyloxytropone (2f) indicated that it formed a head-to-tail dimer through an intermolecular hydrogen bond between the NH and the tropone carbonyl group. The X-ray diffraction study of compound 2f suggested that the molecules formed interdigitated bilayer smectic C phases with a tilt angle of as much as c. 40° to a layer plane. The corresponding benzenoids, however, were non-mesomorphic, with higher melting points than the troponoids. In the troponoids, sigmatropic migration of the benzoyl group weakened the intermolecular hydrogen bonding and assisted the occurrence of mesomorphic properties.     

Synthesis and asymmetric polymerization of (S)‐N‐maleoyl‐L‐leucine propargyl ester

A kind of N‐substituted maleimide (RMI), chiral (S)‐N‐maleoyl‐L ‐leucine propargyl ester ((S)‐PLMI) with a specific rotation of [α]₄₃₅ = ?27.5° was successfully synthesized from maleic anhydride, L ‐leucine, and propargyl alcohol. (S)‐PLMI was polymerized by three polymerization methods to obtain the corresponding optically active polymers. Asymmetric anionic, radical, and transition‐metal‐catalyzed polymerizations were carried out using organometal/chiral ligands, 2,2′‐azobisisobutyronitrile (AIBN) and (bicyclo [2,2,1]hepta‐2,5‐diene) chloro rhodium (I) dimer ([Rh(nbd) Cl]₂), respectively. Poly((S)‐PLMI) obtained by [Rh(nbd)Cl]₂ in DMF showed the highest specific rotation of ?280.6°. Chiroptical properties and structures of the polymers obtained were investigated by GPC, CD, IR, and NMR measurements. Two types of poly((S)‐PLMI)‐bonded‐silica gels as the chiral stationary phase (CSP) were prepared for high‐performance liquid chromatography (HPLC). Their optical resolution abilities were also elucidated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3722–3738, 2007     

Measurement of Neutral pions in √NN=200 GeV and 62.4 GeV Au+Au collisions at RHIC-PHENIX

Neutral pions (π⁰) in √_NN=200 GeV and 62.4 GeV Au+Au collisions were measured at RHIC-PHENIX Year-4 Run. In √_NN=200 GeV, π⁰ spectra are measured up to p _T=20 GeV/c. A strong suppression by a factor of ～5 is observed and stays almost constant up to 20 GeV/c.     

Tris(1,10‐phenanthroline‐N,N′)­iron(II) di­thio­cyanate tri­hydrate

The title mononuclear iron(II) complex, [Fe(C₁₂H₈N₂)₃](NCS)₂·3H₂O, has a slightly distorted octa­hedral coordination. One of the thio­cyanate ions and one of the water mol­ecules of crystallization show positional disorder.     

Synthetic Studies on Ciguatoxin—Synthesis of H–I–J Ring System

Synthesis of a tricyclic ring system corresponding to H–I–J rings of ciguatoxin was stereoselectively achieved in 13 steps from a sugar derivative as a model study directed toward the total synthesis of ciguatoxin.     

Electrochemical etching process to tune the diameter of arrayed deep pores by controlling carrier collection at a semiconductor–electrolyte interface

An approach to control the diameter of high-aspect-ratio pores formed into a silicon wafer by an electrochemical etching process is reported. Hole (h⁺) was involved in the etching reaction and the collection of the h⁺ was the key factor. Artificial micro-cavities were fabricated on the silicon surface prior to the etching. The depth of the space charge region (SCR), Schottky barrier on the silicon-electrolyte interface, was adjusted regarding the depth of the micro-cavities by applied overpotential and specific resistance of the silicon wafer. The collection of h⁺ at the tip of the cavity site was widely controlled by the adjusted SCR. Consequently the electrochemically etched domain at the cavity site was actively tuned, and then high-aspect-ratio pore with the controlled diameter was formed. The diameter was tuned by the SCR depth which was controlled by the overpotential and the specific resistance. The diameter tuning mechanism worked under the mask-free condition.     

Synthesis of Glycocinnasperimicin D

The first total synthesis of amino sugar antibiotic glycocinnasperimicin D ( 1 ) has been achieved by a convergent, three‐component coupling strategy. The key steps involve the Heck–Mizoroki reaction by using the iodophenyl glycoside 50 and acryl amide 32 to furnish the right core structure of 1 , and the construction of the urea glycoside employing the reaction of glycosyl isocyanate 8 with amino sugar 9 . Glycosyl isocyanate 8 was prepared by the oxidation of isonitrile 10 , which displayed excellent reactivity in the coupling event. Synthetic roadblocks, encountered during this synthetic effort, have led to the development of the α‐selective, Lewis acid catalyzed phenyl glycosylation process with 2‐amino‐hexopyranose and a procedure for acetonide deprotection without affecting the silyl ethers.     

Chiral cyclobutane synthesis by exploiting a heteroatom-directed conjugate addition

The syntheses of both enantiomers of cyclobutanes B and ent-B are achieved through heteroatom-directed conjugate addition (HADCA) of nucleophiles to the epoxyvinylsulfone-substituted carbohydrates A and ent-A, which provided carbanions that intramolecularly attacked the epoxide with concomitant formation of the cyclobutane ring.