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Yutaka Aoyagi Kei Ozawa Tatsuya Kobayashi Tomoyo Hasuda Ming-Yu Gui Yong-Ri Jin Xu-Wen Li Haruhiko Fukaya Reiko Yano Yukio Hitotsuyanagi Koichi Takeya 《Tetrahedron》2014
Transformation of plant-origin 7,14-dihydroxy-ent-kaurenes to ent-abietanes having a cis-fused α-methylene γ-lactones was accomplished efficiently under the Mitsunobu reaction conditions. The yields of the desired products were apparently influenced by the steric hindrance at C-1. The cytotoxic activity on P388 murine leukemia cells of the ent-abietanes having cis-fused α-methylene γ-lactones produced were assayed. 相似文献
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An enantioselective total synthesis of sacrolide A, an antimicrobial and cytotoxic fourteen-membered macrolactonic oxylipin isolated from an edible freshwater cyanobacterium, has been accomplished from a known carboxylic acid in 20% overall yield by a concise ten-step sequence. The key transformations include chiral oxazolidinone-based diastereoselective installation of two hydroxy-bearing stereocenters, the Horner–Wadsworth–Emmons olefination to construct the full carbon skeleton, and the Shiina macrolactonization to establish the fourteen-membered macrolide structure. 相似文献
4.
Hiroki Soeda Ryo Towada Yusuke Ogura Tomoyo Mohri Georg Pohnert Shigefumi Kuwahara 《Tetrahedron》2019,75(11):1555-1562
The proposed structure for a moss-produced acetylenic oxylipin (10-keto-type structure) was synthesized from a known glycidol derivative by an 11-step sequence involving epoxide ring opening with a terminal acetylene and enzymatic hydrolysis of a methyl ester intermediate. The NMR spectra of the proposed structure was, however, different from those of the natural oxylipin, which prompted us to synthesize its 9-epi-isomer and two diastereomeric 12-keto-type positional isomers. Comparison of the NMR spectra of the three isomers with those of the natural oxylipin indicated that the natural oxylipin was actually a mixture of the two diastereomeric positional isomers. 相似文献
5.
Li C Winnard PT Takagi T Artemov D Bhujwalla ZM 《Journal of the American Chemical Society》2006,128(47):15072-15073
The conjugate of bacterial cytosine deaminase (bCD) and poly-l-lysine (PLL) that was functionalized with biotin, rhodamine, and Gd3+-DOTA was synthesized and characterized. It demonstrated high relaxivity, improved enzymatic specificity to prodrug 5-fluorocytosine, low cytotoxicity, efficient cell uptake, and high enzymatic stability in fresh mouse serum and human breast cancer cell culture. 相似文献
6.
Murai K Nakamura A Matsushita T Shimura M Fujioka H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(27):8448-8453
A method for conducting enantioselective bromolactonization reactions of trisubstituted alkenoic acids, using the C(3)-symmetric trisimidazoline 1 and 1,3-dibromo-5,5-dimethyl hydantoin as a bromine source, has been developed. The process generates chiral δ-lactones that contain a quaternary carbon. The results of studies probing geometrically different olefins show that (Z)-olefins rather than (E)-olefins are favorable substrates for the process. The method is not only applicable to acyclic olefin reactants but can also be employed to transform cyclic trisubstituted olefins into chiral spirocyclic lactones. Finally, the synthetic utility of the newly developed process is demonstrated by its application to a concise synthesis of tanikolide, an antifungal marine natural product. 相似文献
7.
Dr. Yukio Hitotsuyanagi Masumi Odagiri Saori Kato Jun‐ichi Kusano Tomoyo Hasuda Haruhiko Fukaya Prof. Dr. Koichi Takeya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(10):2839-2846
Two bicyclic hexapeptides, allo‐RA‐V ( 4 ) and neo‐RA‐V ( 5 ), and one cyclic hexapeptide, O‐seco‐RA‐V ( 6 ), were isolated from the roots of Rubia cordifolia L. Their gross structures were elucidated on the basis of spectroscopic analysis and X‐ray crystallography of compound 5 . The absolute stereochemistry of compounds 4 and 5 were established by their total syntheses, and the absolute stereochemistry of compound 6 by chemical correlation with deoxybouvardin ( 3 ). Comparison of the 3D structures of highly active RA‐VII ( 1 ) with less‐active compounds 4 and 5 suggests that the orientation of the Tyr‐5 and/or Tyr‐6 phenyl rings plays a significant role in their biological activity. The isolation of peptides 4 – 6 , along with compound 3 , and the comparison of their structures seem to indicate that peptide 6 may be the common precursor to bicyclic peptides 3 – 5 in the plant. 相似文献
8.
Daisuke Suzuki Tomoyo Yamagata Koji Horigome Kiyoshi Shibata Akira Tsuchida Tsuneo Okubo 《Colloid and polymer science》2012,290(2):107-117
Influence of the gel size on the morphology, phase diagram, and reflection spectroscopy of the colloidal crystals of thermo-sensitive
gel spheres, poly (N-isopropylacrylamide) (pNIPAm), was discussed by adding the data of two gel samples of pNIPAm(400–5) and pNIPAm(600–5) of
412 nm (at 25 °C) and 220 nm (at 45 °C) and of 517 nm (at 20 °C) and 294 nm (at 45 °C), respectively. Colloidal single crystals
formed, but not so large compared with the giant crystals of small pNIPAm gels reported previously. The suspensions even with
ion-exchange resins were turbid and hard to observe the single crystals clearly with the naked eyes as gel size increased.
The critical concentration of melting decreased sharply as the suspensions were deionized with coexistence of the mixtures
of cation- and anion-exchange resins. The critical concentration increased as the gel size increased and/or dispersion temperature
increased. Density of the gel spheres increased as their size increased. These results demonstrated that the colloidal crystallization
takes place by the extended electrical double layers formed around the gel spheres in addition of the excluded volume effect of the gels. Contribution of the electrical double layers on the crystallization increased sharply as temperature increased
and gel concentration decreased, respectively. The contribution also increased slightly as sphere size increased, when comparison
was made at the same gel concentration in wt.%. The present work clarified that the colloidal interfaces, which are inevitable
for the formation of the electrical double layers, are formed between the water phase and gel spheres, though the gel spheres
contain a lot of water molecules at the inner sphere region. 相似文献
9.
Tsuneo Okubo Daisuke Suzuki Tomoyo Yamagata Akihiro Katsuno Masashi Mizutani Hiroshi Kimura Akira Tsuchida 《Colloid and polymer science》2011,289(7):807-816
Drying dissipative patterns were observed at 25 °C, 33 °C, and 45 °C on a cover glass, a watch glass, and a Petri glass dish
during the course of dryness of colloidal crystals of the thermo-sensitive gels of poly(N-isopropylacrylamide) (PNIPA). Two kinds of broad rings, i.e., transparent ring at the outside edge and the ring in the inner
area from the edge, were observed. Sizes of the former were the same as those of the initial liquids irrespective of gel concentration,
whereas sizes of the latter decreased as gel concentration decreased. These broad rings were composed mainly of the monomeric
and the agglomerated gel particles, respectively. Formation of the monodispersed agglomerated particles and their ordered
arrays in the inner area of the dried film were observed especially on a Petri glass dish and a watch glass. The important
role of the electrical double layers formed around the agglomerated particles is supported for the ordering of the agglomerated
particles. The essential differences in the drying patterns between PNIPA gel spheres and the typical colloidal particles
did not appear. 相似文献
10.
Comprehensive analysis system using liquid chromatography-mass spectrometry for the biosynthetic study of peptides produced by cyanobacteria 总被引:2,自引:0,他引:2
Microcystins are hepatotoxic heptapeptides and general tumor promoters produced by several species of the genera Microcystis, Anabaena, Oscillatoria and Nostoc. They are non-ribosomally synthesized via a mixed polyketide synthase/non-ribosomal peptide synthetase system called microcystin synthetase. We have carried out the detection, isolation and structural determination of non-toxic peptides produced together with microcystins by toxic cyanobacteria, which are classified into several groups on the basis of their structures and some of these non-toxic peptides are also non-ribosomally synthesized as well as microcystins. In the present study, we tried to correlate the secondary metabolic peptides produced by the hepatotoxic cyanobacteria with the corresponding peptide synthetase genes. An analytical method using LC-electroscopy ionization MS and photodiode array detection was developed for the exhaustive screening of cyanobacterial peptides in Japanese strains and it was successfully applied to the peptide fractions extracted from these strains. The established method was advantageous over conventional ones using the usual HPLC and matrix-assisted laser desorption ionization time-of-flight MS, because more structural information could be obtained and it is easier to distinguish microcystins from other peptides using this method. Small amounts of other peptides could also be detected by this method. The established method will contribute to the investigation of the relationship between genes encoding the peptide synthetase and secondary metabolic peptides. 相似文献