Synthesis,crystal structure and charge transport characteristics of stable peri-tetracene analogues

peri-Acenes have shown great potential for use as functional materials because of their open-shell singlet biradical character. However, only a limited number of peri-acene derivatives larger than peri-tetracene have been synthesized to date, presumably owing to the low stability of the target compounds in addition to the complicated synthesis scheme. Here, a very simple synthesis route for the tetrabenzo[a,f,j,o]perylene (TBP) structure enables the development of highly stable peri-tetracene analogues. Despite a high degree of singlet biradical character, the compounds with four substituents at the zigzag edge show a remarkable stability in solution under ambient conditions, which is better than that of acene derivatives with a closed-shell electronic configuration. The crystal structures of the TBP derivatives were obtained for the first time; these are valuable to understand the relationship between the structure and biradical character of peri-acenes. The application of peri-acenes in electronic devices should also be investigated. Therefore, the semiconducting properties of the TBP derivative were investigated by fabricating the field-effect transistors.

Highly stable peri-tetracene analogues with a high degree of singlet biradical character were synthesized in a very simple route, and their crystal structures and semiconducting properties were investigated.     

Total Synthesis of Natural PI-091, a New Platelet Aggregation Inhibitor of Microbial Origin

The total synthesis of a new platelet aggregation-inhibiting gamma-lactam PI-091 (1) gave a 1:1 diastereomeric mixture at the gamma-ketal carbon. The high-yielding aldol reaction of an appropriately protected 1,3,4-trihydroxy-4-methyldecan-2-one 42, prepared from D-glucose, with the kinetically generated enolate of 3-methyl-2-butanone provided 43. The resulting diastereomeric mixture of the aldol adduct 43 was converted to a 2,4-alkylated furan 45 via an intramolecular ketalization followed by dehydration. The addition of a singlet oxygen to the alpha-trimethylsilylated furan 48derived from 45 under photochemical conditions efficiently provided an alpha,gamma-dialkylated gamma-hydroxy gamma-lactone 47. The transformation of methyl ketal 52 prepared from 47 into gamma-hydroxy gamma-lactam 53 was achieved by exposure to liquid ammonia in MeOH. The total synthesis of 1 was achieved from 52 through the Dess-Martin periodinane oxidation of the secondary hydroxy group in the side chain. The present total synthesis revealed that the stereogenic carbon center in the side chain in natural 1 is S.     

Formal catalytic asymmetric total synthesis of fostriecin

The common synthetic intermediate of a potent and promising anticancer agent, fostriecin, was synthesized using a unique method that combines four catalytic asymmetric reactions as shown above.     

State of titanium in Ti-containing silica and silicalite catalysts in relation to their oxidation activity

The nature of active titanium species for epoxidation of olefins with H₂O₂ and t-butyl hydroperoxide has been investigated for titanium silicalite (TS-1), titania silica (TiO₂/SiO₂) prepared by a sol-gel method, and titanium oxide supported on silica by a CVD method (TiO₂/SiO₂-CVD). IR and XANES analyses suggested that Ti in TiO₂/SiO₂ and TiO₂/SiO₂-CVD has a tetrahedral configuration bonded to SiO₂ and that in TS-1 has a configuration composed of >Ti=O or related to it. Their configurations are closely related to their reactivities for epoxidation of olefins in which the former works with t-butyl hydroperoxide and the latter with H₂O₂.     

Optical microscopy and in situ Raman scattering of single crystalline ethylene hydrate and binary methane-ethylene hydrate at high pressures

Visual observations through a microscope and in situ Raman measurements have been made for single crystalline ethylene hydrate (EH) and binary methane-ethylene hydrate (MEH) at pressures up to 3.7 GPa and room temperature. Both hydrates showed pressure-induced phase transitions at 1.6, 2.0, and 3.0 GPa for EH and at 1.7, 2.1, and 3.3 GPa for MEH. The cubic sI phase of EH and MEH remains stable up to 1.6 and 1.7 GPa, respectively, which are more widely ranging values than the values for the methane hydrate sI phase. In this sI phase of binary MEH, the cage occupancies by methane and ethylene molecules are investigated from Raman spectra. Above P = 3.0 GPa for EH and 3.3 GPa for MEH, they decomposed by associating with the formation of the polyethylene.     

Synthetic studies directed toward the assembly of the C-glycoside fragment of the telomerase inhibitor D8646-2-6

[reaction: see text] Construction and characterization of the C-glycosidic moiety of telomerase inhibitor D8646-2-6 (1) are described. This is the first example of the C-glycosylation using electron-poor aromatics, 4-hydroxypyrone, as a glycosyl acceptor. The glycosylation reaction and base-promoted isomerization affords desired beta-C-glycoside in a 61% overall yield.     

Electrochemical analysis of single nucleotide polymorphisms of p53 gene

Single nucleotide polymorphisms (SNPs) of cancer repression gene p53 were analyzed electrochemically with ferrocenyl naphthalene diimide (1) as a hybridization indicator. The SNPs studied were the transition to A from G in the codon for amino acid at positions 175, 248 or 273 and the transversion to C from G in the codon for the amino acid at position 72. Thus, 20-meric oligonucleotides carrying the SNP site were used both as a sample and a probe with the latter immobilized on an electrode. Even one base difference on the p53 gene resulted in a significant difference in the current response of 1 and the magnitude of the response correlated with the amount of the DNA hybrid on the electrode. Moreover, when PCR products of exon 4, on which the P72/R72 SNP resides, of the p53 gene were analyzed by this method, the heterozygote and homozygotes were discriminated with modest precision.     

Direct catalytic aldol-type reactions using RCH2CN

[reaction: see text] A copper fluoride-catalyzed cyanomethylation that can be applied to a wide range of ketones and aldehydes was developed using TMSCH(2)CN as a nucleophile. The reaction was extended to a conceptually more advanced copper alkoxide-catalyzed direct addition of alkylnitriles to aldehydes, which can act as a surrogate direct catalytic aldol reaction of esters. These reactions can be applied to the first catalytic enantioselective cyanomethylation of ketones and direct catalytic enantioselective cyanomethylation of aldehydes.     

Purification by HPLC and the UV/Vis absorption spectra of the nitrogen-containing incar-fullerenes iNC60, and iNC70

We report the purification of the nitrogen-containing incar-fullerenes iNC(60) and iNC(70), and their characterisation by UV-Vis absorption spectroscopy.     

Imaging of the bronchial blood flow usingg RI-angiography--study on its procedure and application of dual radioisotope technique (author's transl)

RI-angiography with 99mTcO4- was carried out using a scintillation camera with a digital minicomputer for the purpose of imaging of bronchial blood flow in various lung diseases, and as application of dual radioisotope techniques, other imagings such as tumor imaging with 197HgCl2 or 67Ga-citrate and/or perfusion imaging with 99mTc-MAA, were performed simultaneously in patients remaining the same position, too. The image as a iso-count map extracted out of the image of 197HgCl2, 67Ga-citrate or 99mTc-MAA, was superimposed to the brightness image of RI-anigogram (aortic phase). By these procedures, the image of bronchial blood flow were obtained in some patients with lung cancer, pulmonary tuberculosis, lung abscess, and chronic bronchitis. The dual radioisotope techniques using RI-angiography and the other imaging were useful to make isotope diagnosis of lung diseases more reliable, and the image superimposition methods using RI-angiogram and the image of tumor or perfusion, were useful to improve anatomic orientation of the former.