Yoshihide Usami

Communesins, cytotoxic metabolites of a fungus isolated from a marine alga

Abstract Communesins A and B, exhibiting cytotoxic activity against the cultured P-388 cells, were isolated from the mycelium of a strain of Penicillium sp. stuck on the marine alga Enteromorpha intestinalis . Their structures were elucidated by spectroscopic analyses.

Fumiquinazolines, novel metabolites of a fungus isolated from a saltfish

Abstract Fumiquinazolines A, B and C, exhibiting moderate cytotoxicity, were isolated from the mycelium of a strain of Aspergillus fumigatus which existed in the gastrointestinal tract of the saltwater fish Pseudolabrus japonicus . Their structures were elucidated by spectroscopic and X-ray diffraction analyses and chemical evidence.

Gliocladins A - C and glioperazine; Cytotoxic dioxo- or trioxopiperazine metabolites from a Gliocladium sp. separated from a sea hare

New dioxo- or trioxopiperazine metabolites named gliocladins A-C (1 - 3 ) and glioperazine (4) have been isolated from a strain of Gliocladium sp., originally separated from the sea hare. Their structures have been elucidated by spectroscopic analyses using various NMR spectroscopic techniques. Structurally unique trioxopiperazine (3) exhibited significant cytotoxicity against cultured P388 cells.

A cytotoxic principle of the brown alga Sargassum tortile and structures of chromenes

Abstract Bioassay-directed fractionation of a methanolic extract of the marine alga Sargassum tortile has led to the isolation and characterization of eight compounds which include the new chromenes sargaol, sargasal-II, and sargadiols-I and -II in addition to sargasal-I, hydroxysargaquinone, kjellmanianone, and fucosterol. Among them, hydroxysargaquinone and sargasals-I and -II demonstrated significant and marginal cytotoxicity against cultured P-388 lymphocytic leukemia cells, respectively.

Antineoplastic agents. 551. Isolation and structures of bauhiniastatins 1-4 from Bauhinia purpurea.

Bioassay-guided (P388 lymphocytic leukemia cell line) separation of extracts prepared from the leaves, stems, and pods of Bauhinia purpurea, and, in parallel, its roots, led to the isolation of four new dibenz[b,f]oxepins (2a, 3-5) named bauhiniastatins 1-4, as well as the known and related pacharin (1) as cancer cell growth inhibitors. The occurrence of oxepin derivatives in nature is quite rare. Bauhiniastatins 1-4 were found to exhibit significant growth inhibition against a minipanel of human cancer cell lines, and bauhiniastatin 1 (2a) was also found to inhibit the P388 cancer cell line. Structures for these new cancer cell growth inhibitors were established by spectroscopic techniques that included HRMS and 2D NMR.

Recent synthetic studies leading to structural revisions of marine natural products.

Because of the highly unique structures of marine natural products, there are many examples of structures that were originally proposed based on spectral analyses but later proven incorrect. In many cases, the total syntheses of the originally proposed structures of marine natural products has confirmed their incorrectness and the subsequent total syntheses of the newly proposed structures proved the revised structures. This review will show such cases appearing after 2005 and demonstrate how the true structures were elucidated.

New class azaphilone produced by a marine fish-derived Chaetomium globosum. The stereochemistry and biological activities

Four new metabolites, chaetomugilins P-R and 11-epi-chaetomugilin I, were isolated from a strain of Chaetomium globosum originally obtained from the marine fish Mugil cephalus, and their absolute stereostructures were elucidated on the basis of spectroscopic analyses, including 1D and 2D NMR techniques and various chemical transformations. Particularly, the skeleton of chaetomugilin P is different from that of other azaphilones isolated from this fungal strain to date. In addition, these compounds significantly inhibited the growth of cultured P388, HL-60, L1210 and KB cell lines.

Facile and efficient synthesis of naturally occurring carbasugars (+)-pericosines A and C.

An efficient synthesis of antitumor marine natural product (+)-pericosine A was achieved from (-)-quinic acid in 11.7% overall yield, which is 20 times better than our previously reported synthesis. The crucial steps of this synthesis include the regio- and stereoselective bromohydrination of an unstable diene and the ring opening of an epoxide. This synthetic route was applicable to a synthesis of (+)-pericosine C and also to a synthesis of (-)-pericosine C.

Stereostructure reassignment and determination of the absolute configuration of pericosine D(o) by a synthetic approach.

A combination of chemical synthesis and NMR methods was used to reassign the structure of pericosine D(o) (8), a cytotoxic marine natural product produced by the fungus Periconia byssoides OUPS-N133 that was originally derived from the sea hare Aplysia kurodai. Chemical synthesis was used to prepare pericoisne D(o) (8) from a known chlorohydrin that was in turn derived from (-)-quinic acid. The absolute configuration of natural pericosine D(o) (8) was determined to be methyl (3R,4S,5S,6S)-6-chloro-3,4,5-trihydroxy-1-cyclohexene-1-carboxylate. HPLC analyses using a chiral-phase column indicated that pericosine D(o) (8) exists in an enantiomerically pure form in nature.

Design and synthesis of regioisomerically pure unsymmetrical xanthene derivatives for staining live cells and their photochemical properties

We have demonstrated the synthesis of regioisomerically pure unsymmetrical xanthene derivatives consisting of three units which can be independently modified to control their physical properties. The photochemical properties of the synthetic unsymmetrical xanthene derivatives were investigated in solution by UV-vis absorption and fluorescence measurements, and their cell imaging properties were examined by confocal laser-scanning microscopy.