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Total synthesis of bottromycin A2 can be accomplished through a diastereoselective Mannich reaction of a chiral sulfinamide, mercury-mediated intermolecular amidination, and cyclization of a constrained tetracyclic peptide. Exploitation of this process allowed the synthesis of several novel bottromycin analogs. The antimicrobial activity of these analogs was evaluated in vitro against Gram-positive bacteria, such as methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant enterococci (VRE). Structure–activity relationships were explored taking into consideration the unique three-dimensional structure of the compounds. Notably, one of the new analogs devoid of a methyl ester, which is known to lower the in vivo efficacy of bottromycin, exhibited antibacterial bioactivity comparable to that of vancomycin.

Full details of the initial development and continued examination of a powerful intramolecular palladium(0)-mediated indole annulation for macrocyclization closure of the strained 16-membered biaryl ring system found in complestatin (1, chloropeptin II) and the definition of factors impacting its intrinsic atropodiastereoselectivity are described. Its examination and use in an alternative, second generation total synthesis of complestatin are detailed in which the order of the macrocyclization reactions was reversed from our first generation total synthesis. In this approach and with the ABCD biaryl ether ring system in place, the key Larock cyclization was conducted with substrate 36, containing four phenols, five secondary amides, one carbamate, and four labile aryl chlorides, and provided the product 37 (56%) exclusively as a single atropisomer (>20:1, detection limits) possessing the natural (R)-configuration. In this instance, the complexity of the substrate and the reverse macrocyclization order did not diminish the atropodiastereoselectivity, rather it provided an improvement over the 4:1 selectivity that was observed with the analogous substrate used to provide the isolated DEF ring system in our first generation approach. Just as significant, the atroposelectivity represents a complete reversal of the diasteroselectivity observed with analogous macrocyclizations conducted using a Suzuki biaryl coupling.

The degradation of the mechanical properties of polyimide films was evaluated by means of tensile tests after exposure to a low earth orbit (LEO) environment. Polyimide films irradiated with atomic oxygen (AO), ultraviolet (UV) light, and electron beam (EB) rays using ground simulation facilities were also evaluated similarly and compared. In these experiments tensile stress (7.0 MPa or less) was applied to the samples in order to assess its effects on mechanical properties. The mechanical properties of the flight samples decreased concomitantly with increased exposure duration. The fracture surfaces exhibited characteristic radiated patterns initiating from the exposed surfaces which showed a rough texture. In the AO-irradiated samples the mechanical properties degraded and the surface texture developed as the AO fluence increased; similar fracture surfaces appeared in the flight samples. In contrast, UV and EB irradiation had little impact on mechanical properties. Based on these results, the eroded surfaces by AO irradiation served as the starting points of the rupture, resulting in degradation of mechanical properties of polyimide films exposed to a LEO environment. The tensile stress states induced no difference in evaluations.

Mechanical properties of polyimide films are degraded by exposure to a low earth orbit environment. The main environmental factor for that degradation is atomic oxygen (AO). Using tensile tests, AO-irradiated surface topography observations, and fracture surface analyses, this study investigated the degradation behavior of polyimide films’ mechanical properties by increased AO fluence and its accompanying degradation mechanisms. Tensile strength and elongation of polyimide films were reduced concomitantly with increased AO fluence. Furthermore, AO-irradiated polyimide films fractured from the AO-irradiated surfaces, of which roughness became marked as AO fluence increased. These results reflect that reduction of mechanical properties is attributable to the roughness increase in AO-irradiated surfaces. Polyimide films coated with indium tin oxide (ITO) were also evaluated to confirm the degradation behavior of AO protective films. Surfaces of ITO-coated polyimide films remained smooth even after AO irradiation. However, undercut cavities were formed at ITO coating defect sites. Rupture of ITO-coated polyimide films initiates from the undercut cavities, engendering large reduction of tensile strength and elongation. The degradation of the mechanical properties of ITO-coated polyimide films increased substantially until the undercut cavities fully penetrated the film.

To clarify the effects of space environment on mechanical properties of polymer, exposure experiments were conducted utilizing the International Space Station Russian Service Module. Poly‐ether‐ether‐ketone (PEEK) films under tensile stress were exposed to low Earth orbit (LEO) environment, and reference samples were irradiated with atomic oxygen (AO), electron beam (EB), and ultraviolet light (UV) in ground facilities. By comparing the results of flight and ground tests, the degradation behavior and the influential factors in LEO were investigated. The following results were obtained. (1) UV was found to be the harshest factor in LEO on tensile properties, since it decreased elongation to 15% of pristine sample after 46‐months exposure. (2) AO in LEO eroded the specimen surface with a cone‐like morphology and reduced the thickness; however, it had no significant effect on tensile properties. (3) EB irradiation in LEO had no measurable effects on the material properties.

資料番号: PA0810043000

A new NADH-fumarate reductase inhibitor, verticipyrone, was isolated from the cultured broth of a fungus, Verticillium sp. FKI-1083. The structure was established as (E)-2-methoxy-3,5-dimethyl-6-(3-methyl-2-undecenyl)-4H-pyran-4-one. Verticipyrone exhibited an IC50 value of 0.88 nM against NADH-fumarate reductase of Ascaris suum. Verticipyrone inhibited both Ascaris and bovine heart complex I, and its synthetic analogue, 8,9-dihydro-8-hydroxyverticipyrone, showed good selectivity against Ascaris complex I.

Investigation on the crystallographic orientation relationships among D022-Al3Ti, A15-Mo3Al and high temperature bcc phase consisting of an Al-Mo-Ti ternary alloy with an equi-axed two-phase structure was conducted by FESEM/EBSD analysis. The grains of intermetallic phases have certain crystallographic orientations each other, while the crystallographic orientation distributions become random after a high temperature deformation. This strongly suggests the grain boundary sliding and grain rotating govern the high temperature deformation, which is consistent with the fact that the strain-rate sensitivity m is 0.3 or higher during a steady-state compressive deformation.

The high temperature deformation behavior of two-phase intermetallic-based alloys composed of the D0 22 -Al 3 Ti and A15-Mo 3 Al phases is investigated. It is found that the equi-axed two-phase structure formed by an isothermal heat treatment is very stable even after a high-temperature heat treatment and, moreover, the microstructure is retained even after heavy deformation at high temperature. The strain-rate sensitivity m is 0.3 or higher, and a steady state deformation is attained. Compressive deformability is found to be extremely high with the equi-axed two-phase structure. Conversely, a lamellar structure was found to be unstable during deformation. The strain-rate sensitivity m of the specimens with a lamellar structure is almost the same as that of the equi-axed two-phase structure, and the resulting microstructure strongly suggests that the deformation is concentrated at the boundaries between the lamellar colonies, where the equi-axed two-phase structure is formed during deformation by spheroidization.

The surface textures of polyimide (PI) films exposed to a low Earth orbit environment in the “SM and JEM/MPAC&SEED experiments” and PI films irradiated by atomic oxygen (AO) using a ground facility were quantitatively evaluated. Additionally, the degradation in tensile strength of these PI films was assessed in terms of the surface texture changes. The exposed surfaces of the flight PI films were contaminated by silicon oxide layers and included some local valleys, or extremely deep depressions compared with the surrounding areas. The depth of the deepest local valleys on the exposed surfaces (a 0max ), which were predicted by extreme statistics, exceeded those of the local valleys of the AO-irradiated PI films. When the tensile strength of these PI films was plotted against AO fluence, the tensile strength reduction trends clearly differed for each PI film. However, the reduction trends were shown to closely correlate when the tensile strengths were plotted against a 0max . These results mean that the tensile strength of the PI films attacked by AO can be evaluated based on the depth of surface cracks and that fracture mechanics is considered an effective tool to predict tensile strength reduction.

A space materials exposure experiment was conducted on the exterior of the International Space Station (ISS) using the Micro-Particles Capturer and Space Environment Exposure Device (MPAC&SEED) of the Japan Aerospace Exploration Agency (JAXA). The MPAC&SEED experiments were aboard both the Russian Service Module (SM/MPAC&SEED) and the exposed Facility of the Japanese Experiment Module, KIBO Exposed Facility (JEM/MPAC&SEED). The JEM/MPAC&SEED was attached to the Space Environment Data Acquisition Equipment-Attached Payload (SEDA-AP).

Extreme ultraviolet (EUV) spectrum emitted from laser-sustained oxygen plasma in a laser detonation atomic oxygen beam source was investigated. In order to measure EUV spectra, specially designed flat-field grazing-incidence EUV spectrometer was designed. The EUV spectra were recorded on an imaging plate which provides quantitative analysis capability. It was confirmed that EUV emission in the range of 20 –50 nm was included in the emission from laser-sustained oxygen plasma in a laser detonation source. The experimental results clearly indicated that the EUV intensity depends strongly on the translational energy of atomic oxygen. Even though the effect of EUV on the material erosion has not been confirmed, presence of high-energy photon need to be considered for better understanding of the reaction of hyperthermal atomic oxygen in the ground-based facility.

The first total synthesis of chloropeptin II (1, complestatin) is disclosed. Key elements of the approach include the use of an intramolecular Larock indole synthesis for the initial macrocyclization, adopting conditions that permit utilization of a 2-bromoaniline, incorporating a terminal alkyne substituent (-SiEt(3)) that sterically dictates the indole cyclization regioselectivity, and benefiting from an aniline protecting group (-Ac) that enhances the atropdiastereoselectivity and diminishes the strained indole reactivity toward subsequent electrophilic reagents. Not only did this key reaction provide the fully functionalized right-hand ring system of 1 in superb conversion (89%) and good atropdiastereoselectivity (4:1 R:S), but it also represents the first reported example of what will prove to be a useful Larock macrocyclization strategy. Subsequent introduction of the left-hand ring system enlisting an aromatic nucleophilic substitution reaction for macrocyclization with biaryl ether formation completed the assemblage of the core bicyclic structure of 1. Intrinsic in the design of the approach and by virtue of the single-step acid-catalyzed conversion of chloropeptin II (1) to chloropeptin I (2), the route also provides a total synthesis of 2.

Effects of atomic oxygen (AO) on mechanical properties of polyimide films were investigated using surface topography observations and tensile tests. The ITO‐coated polyimide films, which are expected to have a high durability against AO attacks, were also evaluated. Surfaces of polyimide films irradiated by AO were deeply eroded, exhibiting a rough texture. The roughness developed as the AO fluence increased. Tensile strength and elongation of the polyimide films degraded after AO irradiation tests. In addition, that degradation became marked concomitantly with increased AO fluence. These results indicate that development of surface roughness can degrade mechanical properties of polyimide films. In contrast, surfaces of ITO‐coated polyimide films remained flat and were hardly affected by AO irradiation. Nevertheless, the tensile strength and elongation of ITO‐coated polyimide films were decreased by AO irradiation. Such degradation resulted from undercut cavities formed by AO erosion at the defects sites of ITO coating.

A space materials exposure experiment was condcuted on the exterior of the Russian Service Module (SM) of the International Space Station (ISS) using the Micro‐Particles Capturer and Space Environment Exposure Device (MPAC&SEED) of the Japan Aerospace Exploration Agency (JAXA). Results reveal artificial environment effects such as sample contamination, attitude change effects on AO fluence, and shading effects of UV on ISS. The sample contamination was coming from ISS components. The particles attributed to micrometeoroids and/or debris captured by MPAC might originate from the ISS solar array. Another MPAC&SEED will be aboard the Exposure Facility of the Japanese Experiment Module, KIBO Exposure Facility (EF) on ISS. The JEM/MPAC&SEED is attached to the Space Environment Data Acquisition Equipment‐Attached Payload (SEDA‐AP) and is exposed to space. Actually, SEDA‐AP is a payload on EF to be launched by Space Shuttle flight 2J/A. In fact, SEDA‐AP has space environment monitors such as a high‐energy particle monitor, atomic oxygen monitor, and plasma monitor to measure in‐situ natural space environment data during JEM/MPAC&SEED exposure. Some exposure samples for JEM/MPAC&SEED are identical to SM/MPAC&SEED samples. Consequently, effects on identical materials at different positions and operation periods of ISS will be evaluated. This report summarizes results from space environment monitoring samples for atomic oxygen analysis on SM/MPAC&SEED, along with experimental plans for JEM/MPAC&SEED.

Polymermaterials exposed to a space environment exhibit strongly degraded properties because of environmental factors, for example, atomic oxygen, vacuum ultraviolet, and radiation. In addition, the degradation of polymer materials can be accelerated because of the synergistic effects of these environmental factors. For designing highreliability spacecraft, it is important to understand precisely the polymer materials’ degradation. In this report, the synergistic effects of atomic oxygen and vacuum ultraviolet on polyimide films, Kapton H, and silver-coated fluorinated ethylene propylenefilmswere investigated through comparison of the degradation behaviors after single, sequential, and simultaneous irradiations. For both materials, there was no significant change attributed to the synergistic effects in erosion yield and thermo-optical properties. However, the surface morphology of silver-coated fluorinated ethylene propylene changed substantially depending on the irradiationmethod. Surfaces of silver-coated fluorinated ethylene propylene were eroded by atomic oxygen, but were smoothed by vacuum ultraviolet. The surface morphology after sequential irradiations differed depending on the irradiation sequence. A rougher surface with low blunt cones was produced after simultaneous irradiation because of the interaction of the erosion by atomic oxygen attacks and smoothing by vacuum ultraviolet irradiation. This report also describes the measurement methods for fluence of each beam under simultaneous irradiation.

[reaction: see text] Total synthesis of verticipyrone, a novel NADH-fumarate reductase inhibitor, has been accomplished by a convergent approach using novel "Reverse Julia olefination" method. During total synthetic studies, we also prepared and evaluated several synthetic verticipyrone analogues, some of which exhibited more potent antiparasitic activity than the natural verticipyrone.

In Japan, the largest material exposure program “SM/MPAC&SEED (Service Module/ Micro-Particles Capturer and Space Environment Exposure Device) Experiment” has been completed. This program is quite ambitious among the other Japanese materials exposure tests; 3 sets of samples have been exposed for 1, 2 and 3 years in orbit in order to discover the fluence dependence of the material responses. We have learned a lot of lessons from this program. Based on the lessons learned, the “Advanced Material Exposure Test Working Group” has been established by the Committee on Space Utilization in 2007. This working group discussed the current problems of the material exposure program (flight tests) and proposed the future direction of the experimental methodologies. In this presentation, problems and new challenges discussed in this working group will be discussed., ISTS Special Issue: Selected papers from the 27th International Symposium on Space Technology and Science

Thermal control materials such as white paints and germanium-coated polyimide film were evaluated with respect to their space environmental tolerance for materials selection of the Dual-frequency Precipitation Radar of the Global Precipitation Measurement satellite (GPM/DPR). Though peeling off and cracking occurred in one paint material during the thermal shock test, other paints showed good tolerance against thermal shock, atomic oxygen, and ultraviolet ray irradiation. Germanium coating on polyimide film was also verified as high atomic oxygen tolerant barrier. Comparing different thickness germanium coatings, it seems that a 1000 angstrom Germanium film has fewer defects and risk of AO undercutting than a 525 angstrom Germanium film.