Hitomi Yamada

Stereocontrolled synthesis of an indole moiety of sespendole and stereochemical assignment of the side chain.

Two possible diastereomers of the indole moiety of sespendole were synthesized from 3-hydroxy-4-nitrobenzaldehyde in a highly stereoselective manner. Comparison of (1)H and (13)C NMR spectra of the two synthetic materials with those sespendole leads us to propose that the relative stereochemistry of the epoxyalcohol is syn.

Modified synthesis and supramolecular polymerization of rim-to-rim connected bisresorcinarenes.

The acid-catalyzed condensation reaction of resorcinol and bisdimethoxyacetals gave rise to rim-to-rim connected bisresorcinarenes in good yields. In the presence of ethanol, the homoditopic bisresorcinarenes assembled to form supramolecular polymers via hydrogen bonding interactions. The fibrous morphologies of the supramolecular polymers were confirmed by atomic force microscopy and scanning electron microscopy.

Gold particles containing plasma-polymerized styrene as an X-ray absorber

Gold particles containing plasma-polymerized styrene film were formed simultaneously by plasma polymerization and evaporation using an inductively coupled argon gas flow type reactor. Gold was used as the evaporated metal and styrene as the monomer. The plasma etching characteristics of the film were evaluated by O2 and CO2 plasmas using a reactor with parallel-plate electrodes. A structure of lines and spaces of 4μm width was successfully fabricated in the film on Si wafer by CO2 plasma etching through a mask pattern of plasma-polymerized resist. A self-developed pattern was obtained through the X-ray mask with polyimide substrate by synchrotron radiation. The molecular structure and atomic composition of the film were investigated by ESCA and TEM.

Stereocontrolled Total Synthesis of Polygalolide A

The total synthesis of polygalolide A, a secondary metabolite that was isolated from a Chinese medicinal plant, is reported. A key issue in this synthesis was construction of an oxabicyclo[3.2.1] skeleton, which was solved by the development of an intramolecular Ferrier-type C-glycosylation of a glucal with siloxyfuran as an internal nucleophile. The substrate was prepared from D-glucal by the introduction of trimethylsilylacetylene and siloxyfuran groups. Although C-glycosylation did not occur under the conditions found from model experiments, further examination revealed that the combination of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and 2,4,6-collidine successfully afforded the desired product as a single diastereomer. The siloxy group at the C3 position played a crucial role in the stereocontrol of this reaction. The product was further transformed into a tetracyclic compound as follows: The vinyl ether and acetylenic moieties were reduced and the siloxy group was removed with a Barton-McCombie reaction. The construction of the six-membered ether and the γ-lactone provided the tetracyclic compound. Finally, a phenolic moiety was introduced by using a Mukaiyama aldol reaction to furnish polygalolide A.

Stereocontrolled synthesis of the oxathiabicyclo[3.3.1]nonane core structure of tagetitoxin

Tagetitoxin is an unusually densely functionalized natural product, consisting of an unprecedented oxathiabicyclo[3.3.1]nonane ring system possessing acetate, phosphate, amide, carboxylic acid, and amine groups with six contiguous asymmetric centers. A fully functionalized core structure of tagetitoxin was synthesized from tri-O-acetyl-D-galactal in a highly stereoselective manner.

Total Synthesis of Polygalolide A

The total synthesis of polygalolide A was accomplished through intramolecular C-glycosylation of glucal modified with siloxyfuran. The siloxyfuran group and siloxy substituent at the C-3 position played crucial roles in allowing direct access to the highly substituted oxabicyclo[3.2.1] core skeleton with correct quaternary stereogenic centers.

Polystyrene thin film formed by synchrotron radiation chemical vapor deposition

Formation of polystyrene thin film by the synchrotron radiation chemical vapor‐deposition method was investigated using a styrene monomer. Polystyrene film was deposited at the irradiated area and vicinity along the irradiated area on a Si substrate. The deposition rate depended on the monomer gas pressure, substrate temperature, and x‐ray wavelength. Polystyrene film at the irradiated area was insoluble in benzene solvent, while that at the unirradiated area was easily dissolved. A patterned film deposition could be successfully performed under an irradiation of synchrotron radiation through a Ni mesh mask. The pattern profile was influenced by the gap length between the Si substrate and mask and a clear pattern was obtained after benzene treatment.

Oxygen plasma etching resistance of plasma polymerized organometallic film

The oxygen plasma etching resistance of plasma polymerized organometalic film was measured. The films were deposited by downstream plasma deposition using gaseous mixtures of an organic monomer (C3H6) and a metal‐containing monomer tetramethyltin or tetramethylsilane. By changing the flow‐rate ratio of both monomers, the metal content of the film was reproducibly varied from 0% to 27%. It was found that the O2 reactive ion etching rate depended on metal content in polymer, discharge power density, and oxygen gas pressure. High oxygen plasma etching resistance was obtained for films which contained even a few percent of metal. From the results of electron spectroscopy for chemical analysis and Auger electron spectroscopy measurements, it was observed that the metal‐oxidized layer was formed on the surface during oxygen plasma etching.

Dry Developable Plasma Polymerized Photo-Resist System For Curved Surface Fabrication

Dry-developable single layer resist process using plasma polymerized film was investigated. For the process, the selective fixation of Si-containing organic monomer to base polymer at the exposed part was applied. Plasma polymerized film was formed by an inductively coupled gas flow type reactor. Si-containing monomer was diffused to a base polymer in the sealed reactor under the pressure of several Torr at RT. The contrast of Si-containing monomer between the exposed and unexposed parts was attained by expelling the unreacted monomer at the unexposed part after pattering exposure. The pattern formation was performed through the process using SR as a pattering source. The 1-1.5um pattern was obtained by O2 RIE. An investigation about the diffusion level of Si-containing monomer was conducted by IR and ESCA depth-profile.

X-ray absorbing and mechanical properties of Au-C film for x-ray mask absorber

The X-ray absorption and mechanical properties of gold containing (Au-C) absorber formed on polyimide membrane for X-ray lithography mask have been investigated. The Au-C films were deposited by the same method as the previous investigators(Itoh et al.)1. (1) The compositional dependence of film stress before and after the exposure to SOR radiation has been observed. As a result, the stress in film changed monotonically ranging from compression (-3xlO8N/m2) to tension (l.2xlO8N/m2) with increasing Au content. Zero film stress was observed at Au atomic composition of 30%. Films originally being compressive (-l.5xlO7N/m2) were found to become tensile (l.OxlO8N/m2) after absorbing l500J/cm3 X-ray. This tendency differs from that of the BN film observed by King et al (2) X-ray absorption ratio in Au-C films were determined by measuring the amount of reduced thickness of resist on development after the exposure of X-ray through Au-C films with various composition ratios. It was found that it tended to fall from 92% to 68% with a decrease of Au atomic composition ratio from 0.85 to 0.11 at the constant absorber thickness of 0.5 pm. (3) Au-C films of various atomic composition ratio were patterned with EB lithography using the PMMA(Polyrnethylmethacrylate) resist and Reactive Ion Etching (RIE) with 02 gas. It was found that the etching rate of the film decreases with increasing Au content. The typical obtained value was approximately 100A/min at around 50% to 60% of Au composition and this was about 4 times higher than etching rate of pure Au. It is concluded that the Au-C absorber on polyimide membrane X-ray mask is practical for VLSI use for submicron pattern fabrication.