Nobuaki Matsumori

Isolation and chemical structure of amphidinol 2, a potent hemolytic compound from marine dinoflagellate Amphidinium klebsii

Abstract A new polyene-polyhydroxy compound, amphidinol 2 ( 2 ), was isolated as a potent hemolytic and antifungal agent from a cultured strain of dinoflagellate Amphidinium klebsii . The structure elucidated by spectroscopic methods turned out to be partly analogous to amphidinol 1 ( 1 ), which had been reported from the different strain of A. klebsii .

Conformational analysis of natural products using long-range carbon-proton coupling constants: Three-dimensional structure of okadaic acid in solution

Abstract Long-range carbon-proton coupling constants ( 2,3 J C,H ) are known to depend on the dihedral angles as is the well-known case with interproton couplings. The precise measurement of these J values were carried out using hetero half-filtered TOCSY and phase-sensitive HMBC on a marine natural product, okadaic acid. From the obtained values together with 3 J H,H we disclosed the conformations of okadaic acid in organic and aqueous solutions (CD 3 OD-CDCl 3 or NaOD/D 2 O), which resembled each other and that obtained for its crystalline o -bromobenzyl ester. The successful result in the present conformational study, even though as an exmaple, demonstrated this methodology to be powerful in elucidation of conformations and configurations of acyclic or macrocyclic portions in natural products of this size.

Long-range carbon-proton coupling constants for stereochemical assignment of acyclic structures in natural products: Configuration of the C5C9 portion of maitotoxin

Abstract Long-range carbon-proton coupling constants (2,3JC,H) were measured for maitotoxin (MTX), one of the largest natural non-biopolymers, by hetero-half filter experiments and phase-sensitive HMBC with use of 9 mg of a 4% 13C-enriched sample. The necessary coupling constants within the terminal acyclic portions of MTX, where NOE analysis was not successful owing to the presumed coexistence of multiple conformers, were thus obtained for the resultant elucidation of relative configurations for the acyclic stereogenic centers to be 5R ∗ , 7R ∗ , 8R ∗ , and 9S ∗ .

Stereochemical assignment of the C35-C39 Acyclic linkage in maitotoxin: completion of stereochemical determination of C15-C134

The relative configuration of carbons within the C35–C39 acyclic linkage of maitotoxin (MTX) was assigned by synthesis of stereodefined model compound 1 and its comparison with MTX in 1H and 13C NMR spectra. This result completed Stereochemical assignments of the whole molecule except for side chains.