Faculty Profiles - KUBOTA Takaaki

27 Structure Elucidation and Biosynthetic Studies of Amphezonol A, a Novel Polyhydroxyl Metabolite from Symbiotic Marine Microalga

Kubota Takaaki, Sakuma Yusuke, Shimbo Kazutaka, Tsuda Masashi, Uozumi Yasuhiro, Kobayashi Jun'ichi

Symposium on the Chemistry of Natural Products, symposium papers 47 ( 0 ) 151 - 156 2005

Language：Japanese Publisher：Symposium on the Chemistry of Natural Products Steering Committee

DOI： 10.24496/tennenyuki.47.0_151

Absolute Stereochemistry of Amphidinolide E.

KUBOTA TAKAAKI, TSUDA MASASHI, KOBAYASHI JUN'ICHI

日本化学会講演予稿集 81st ( 2 ) 707 2002.3

Studies on biosynthesis of amphidinolides.

TSUDA MASASHI, KUBOTA TAKAAKI, SHIMBO KAZUTAKA, HORIGUCHI TAKEO, KATSUMATA KAZUHITO, KOBAYASHI JUN'ICHI

日本化学会講演予稿集 80th 3 2001.9

沖縄産海綿Suberea sp.より単離した新規ブロモチロシンアルカロイドMa′edamine AとBの構造

久保田高明, 津田正史, 平野敬子, 渡部賢二, 小林淳一

日本薬学会年会要旨集 121年会 ( 2 ) 119 - 119 2001.3

17 Stereochemistry of Amphidinolides C and T1〜T5

Kubota Takaaki, Tsuda Masashi, Endo Tetsuya, Shiro Motoo, Kobayashi Jun'ichi

Symposium on the Chemistry of Natural Products, symposium papers 43 ( 0 ) 97 - 102 2001

Language：Japanese Publisher：Symposium on the Chemistry of Natural Products Steering Committee

Amphidinolide C (1) is a unique 25-membered macrolide isolated from a marine dinoflagellate Amphidinium sp. (strain Y-5). The gross structure of 1 has been elucidated by 2D-NMR data, whereas the stereochemistry remains undefined. During our search for bioactive metabolites from marine dinoflagellates, relatively large amounts of 1 have been recently isolated from two strains (Y-56 and Y-71) of the genus Amphidinium, which allowed us to investigate the stereochemistry of 1 Absolute configurations at C-12, C-13, C-20, C-23, C-24, and C-29 of amphidinolide C (1) were assigned by combination of NMR analyses including J-based configuration analysis and Mosher's method, while absolute configurations at C-7 and C-8 of 1 were assigned by application of Mosher's method for erythro glycol and comparison of ^1H-NMR data of natural specimen with those of synthetic C-1-C-10 segments. Absolute configurations at C-3, C-4, C-6, and C-16 of 1 were elucidated by comparison of NMR data of degradation products of 1 with synthetic C-1-C-7 and C-16-C-18 segments. On the other hand, five new 19-membered macrolides amphidinolides T1-T5 (2-6) have been isolated from the Y-56 and Y-71 strains of the genus Amphdinium. The gross structures were elucidated by 2D-NMR analyses. Absolute configurations at C-2, C-13, C-14, and C-18 of amphidinolide T1 (2) were assigned on the basis of NMR data of the MTPA esters of 2 and those of degradation products of 2, while absolute configurations at C-7, C-8, and C-10 of 2 were elucidated by comparison of ^1H-NMR data of C-1-C-12 segment with those of synthetic model compounds for tetrahydrofuran portion. The absolute stereochemistry of amphidinolides T2-T5 (3-6) were also elucidated by similar methods. The stereostructure of 2 was also confirmed by a single crystal X-ray diffraction analysis.

DOI： 10.24496/tennenyuki.43.0_97

17 Stereochemistry of Amphidinolides C and T1〜T5

Kubota Takaaki, Tsuda Masashi, Endo Tetsuya, Shiro Motoo, Kobayashi Jun'ichi

Symposium on the Chemistry of Natural Products, symposium papers 43 ( 0 ) 97 - 102 2001

Language：Japanese Publisher：Symposium on the Chemistry of Natural Products Steering Committee

DOI： 10.24496/tennenyuki.43.0_97

Two New Cyclic Depsipeptides from Okinawan Marine Sponge Theonella sp.

SHIMBO KAZUTAKA, KUBOTA TAKAAKI, TSUDA MASASHI, KOBAYASHI JUN'ICHI

日本化学会講演予稿集 78th ( 2 ) 849 2000.3

Amphidinolide V, Novel 14-Membered Macrolide from Marine Dinoflagellate Amphidinium sp.

KUBOTA TAKAAKI, TSUDA MASASHI, KOBAYASHI JUN'ICHI

日本化学会講演予稿集 78th ( 2 ) 884 2000.3

100(P48) Colopsinols A and B, Novel Polyhydroxyl Metabolites from Marine Dinoflagellate Amphidinium sp.

Kubota Takaaki, Tsuda Masashi, Takahashi Miho, Ishibashi Masami, Kobayashi Jun'ichi, Naoki Hideo

Symposium on the Chemistry of Natural Products, symposium papers 41 ( 0 ) 595 - 600 1999

Language：Japanese Publisher：Symposium on the Chemistry of Natural Products Steering Committee

Marine dinoflagellates of the genus Amphidinium have been recognized as a rich source of novel bioactive substances with unique structures. We previously isolated a series of cytotoxic macrolides, designated amphidinolides, possessing unique structural features from several strains of the dinoflagellates Amphidinium sp., among which the strain Y-5 was the richest source of the amphidinolides. Further search for metabolites from the strain Y-5, which was a symbiont of Okinawan marine acoel flatworm Amphiscolops sp., resulted in the isolation of two novel polyhydoroxyl compounds, colopsinols A (1) and B (2), belonging to a new class of polyketide metabolites. The structures of 1 and 2 were elucidated on the basis of extensive NMR techniques including a newly developed 2D NMR experiments such as CH_2-selected editing HSQC (E-HSQC) as well as FABMS/MS data. Colopsinols A (1) and B (2) are new class of polyketide natural products consisting of C_<56> and C_<53>-liner carbon chains, respectively, possessing a gentiobioside (β-D-glucopyranosyl-(1-6)-β-D-glucopyranoside) moiety and a sulfate ester. From this strain (Y-5), 13 cytotoxic macrolides, amphidinolides A-D, J, K, and M-S, have been isolated so far. Biosynthetically it is interesting that quite different type of polyketides such as colopsinols and amphidinolides are produced from the same dinoflagellate. Colopsinol A (1) showed inhibitory activity against DNA polymerase α and β with IC_<50> values of 13 and 7μM, respectively.

DOI： 10.24496/tennenyuki.41.0_595

100(P48) Colopsinols A and B, Novel Polyhydroxyl Metabolites from Marine Dinoflagellate Amphidinium sp.

Kubota Takaaki, Tsuda Masashi, Takahashi Miho, Ishibashi Masami, Kobayashi Jun'ichi, Naoki Hideo

Symposium on the Chemistry of Natural Products, symposium papers 41 ( 0 ) 595 - 600 1999

Language：Japanese Publisher：Symposium on the Chemistry of Natural Products Steering Committee

DOI： 10.24496/tennenyuki.41.0_595

Structure of new polyol compound Luteophanol B isolated from Gonyaulax Amphidinium species.

KUBOTA TAKAAKI, TSUDA MASAFUMI, DOI YUKIKO, NAKAMICHI HIROKO, ISHIBASHI MASAMI, KOBAYASHI JUN'ICHI

日本薬学会年会要旨集 118th ( 2 ) 108 1998.3

80(P63) Luteophanols B and C, New Polyhydroxyl Compounds from Marine Dinoflagellate

Kubota Takaaki, Tsuda Masashi, Doi Yukiko, Takahashi Ayako, Nakamichi Hiroko, Ishibashi Masami, Fukushi Eri, Kawabata Jun, Kobayashi Jun'ichi

Symposium on the Chemistry of Natural Products, symposium papers 40 ( 0 ) 473 - 478 1998

Language：Japanese Publisher：Symposium on the Chemistry of Natural Products Steering Committee

During our continuing search for structurally unique secondary metabolites from marine dinoflagellates, we previously isolated a series of cytotoxic macrolides, amphidinolides, from dinoflagellates Amphidinium sp. Recently we investigated another strain of Amphidinium sp. (strain number Y-52), which was isolated from the inside cells of the Okinawan marine acoel flatworm Pseudaphanostoma luteocoloris, and isolated two new polyhydroxyl compounds, luteophanols B (1) and C (2), both consisting of a C_<64>-linear aliphatic chain. The structure elucidation of 1 and 2 were elucidated on the basis of chemical degradation and newly developed 2D NMR experiments, E-HSQC and E-HSQC-TOCSY. E-HSQC and E-HSQC-TOCSY are very useful techniques for structure elucidations of complex natural products possessing many aliphatic methine and methylene carbons such as luteophanols B (1) and C (2). CH_2-selected E-HSQC-TOCSY^6 experiments seem to be suitable to assign very closely resonated carbon signals, since this method affords the high resolution in F_1 axis by limiting the F_1 spectral width, in which sp^2 methylene carbons are resonated.

DOI： 10.24496/tennenyuki.40.0_473