Haruaki Ishiyama

Lyconadins D and E, and complanadine E, new Lycopodium alkaloids from Lycopodium complanatum

Three new Lycopodium alkaloids, lyconadins D (1) and E (2), and complanadine E (3), were isolated from the club moss Lycopodium complanatum. Lyconadin D (1) was the first example of fastigiatine-type alkaloid isolated from Lycopodium complanatum. The structures and relative stereochemistry of 1-3 were elucidated on the basis of spectroscopic data. Complanadine E (3) enhanced mRNA expression for NGF.

Absolute stereochemistry of amphidinolide B

The absolute configurations at eight chiral centers in amphidinolide E (1), a cytotoxic 19-membered macrolide isolated from a marine dinoflagellate Amphidinium sp., were determined to be 2R, 7R, 8R, 13S, 16S, 17R, 18R, and 19R on the basis of detailed analysis of NMR data and by chemical means.

Asymmetric synthesis of double bond isomers of the structure proposed for pyrinodemin A and indication of its structural revision.

Asymmetric synthesis of double bond isomers (+)-2 (Δ15’,16’) and (+)-3 (Δ14’,15’) of the structure (1) (Δ16’,17’) proposed for pyrinodemin A, a cytotoxic bis-pyridine alkaloid with a unique cis-cyclopent[c]isoxazolidine moiety from a marine sponge, has been accomplished. Pyrinodemin A was indicated to be a 1:1 racemic mixture of 2 from comparison of C18 and chiral HPLC analysis for pyrinodemin A and the synthetic compounds as well as ESIMS data of oxidative degradation products of pyrinodemin A.

Halichonadin F and the Cu(I) complex of halichonadin C from the sponge Halichondria sp.

A new sesquiterpenoid with an aromadendrane skeleton, halichonadin F (1), and the Cu(I) complex of haliconadin C (2) were isolated from a marine sponge Halichondria sp., and the structures and relative stereochemistries of 1 and the complex of 2 were elucidated on the basis of spectroscopic data and chemical methods.

SYNTHESIS OF C-1 C-13 SEGMENT OF AMPHIDINOLIDE B

Abstract The C-1 ∼ C-13 segment (2) of amphidinolide B (1), a potent cytotoxic 26-membered macrolide, has been synthesized.

Eudistomidin G, a new β-carboline alkaloid from the Okinawan marine tunicate Eudistoma glaucus and structure revision of eudistomidin B

A new beta-carboline alkaloid, eudistomidin G (1), has been isolated from the Okinawan marine tunicate Eudistoma glaucus, and the structure was elucidated from spectroscopic data. Furthermore, the structure of eudistomidin B (2), which has been isolated from the same tunicate, was revised from 2a to 2b by detailed analyses of spectroscopic data. Asymmetric synthesis of the revised structure (2b) of eudistomidin B (2) and its (1S,10S)-diastereomer (2c) has been accomplished with the Noyori catalytic asymmetric hydrogen-transfer reaction. The absolute configuration of eudistomidin B (2) was confirmed to be 2b possessing (1R,10S)-configuration, from comparison of the (1)H NMR data, CD spectra, [alpha](D) values, and HPLC analysis of 2b, 2c, and natural eudistomidin B.

Stereochemistry of iejimalide B

Abstract The absolute configurations at five chiral centers, except for C-32( S ) reported previously, in iejimalide B ( 1 ), a potent cytotoxic 24-membered macrolide isolated from a tunicate Eudistoma cf. rigida , were assigned as 4 R , 9 S , 17 S , 22 S , and 23 S on the basis of detailed analysis of NMR data and chemical means. Furthermore, the structure of iejimalide B was revised from 2 (original: 13 E ) to its 13 Z -isomer ( 1 ).

Total synthesis of amphidinolide Q.

Asymmetric synthesis of amphidinolide Q, a cytotoxic macrolide from the cultured dinoflagellate Amphidinium sp., has been accomplished with Julia coupling, Myers alkylation, and Yamaguchi lactonization. The absolute configuration of amphidinolide Q was confirmed to be 1 from comparison of the NMR data and [alpha](D) values of synthetic and natural amphidinolide Q.

Petiolins A-C, phloroglucinol derivatives from Hypericum pseudopetiolatum var. kiusianum

Two new phloroglucinol derivatives possessing chromane skeleton, petiolins A (1) and B (2), and a new phloroglucinol derivative containing a dihydrofuran ring, petiolin C (3), were isolated from aerial parts of Hypericum pseudopetiolatum var. kiusianum. The gross structures of 1-3 were elucidated by spectroscopic data, and the relative stereochemistry of 3 was elucidated by NOESY data. Petiolins A-C (1-3) showed modest cytotoxicity, while petiolin C (3) exhibited antifungal activity.

Synthesis of eudistomin D analogues and its effects on adenosine receptors.

Six analogues (1-6) of eudistomin D, a beta-carboline alkaloid from a marine tunicate Eudistoma olivaceum, were synthesized, and their affinity and selectivity for adenosine receptors A(1), A(2A), and A(3) were examined. All the synthetic compounds 1-6 did not show affinity to the adenosine A(1) receptor. Delta-carboline 3 exhibited the most potent affinity to the adenosine receptor A(3) among compounds 1-6. Delta-carbolines 3 and 4 showed better affinity than the corresponding beta-carbolines 1 and 2, respectively, while N-methylation (2, 4, and 6, respectively) of the pyrrole ring in 1, 3, and 5 resulted in the reduced affinity to the adenosine A(3) receptor. On the other hand, an eudistomin D derivative, BED, exhibited modest affinity to all the receptors A(1), A(2A), and A(3) but no selectivity.