Kanamienamide, an enamide with an enol ether, was isolated from the marine cyanobacterium Moorea bouillonii. The gross structure was established by spectroscopic analyses, and the relative stereochemistry was elucidated on the basis of the analyses of NOESY correlations and H-H coupling constants. The absolute configuration was determined on the basis of the chiral HPLC analysis of the N-Me-Leu derived from kanamienamide. This is the first report of a natural product that possesses an N-Me-enamide adjacent to an enol ether. Kanamienamide showed growth-inhibitory activity toward HeLa cells with an IC value of 2.5 μM and induced apoptosis-like cell death.
In the search for new antiprotozoal substances, hoshinolactam, an antitrypanosomal lactam, was isolated from a marine cyanobacterium. The gross structure was elucidated by spectroscopic analyses, and the absolute configuration was determined by the first total synthesis. Hoshinolactam showed potent antitrypanosomal activity with an IC value of 3.9 nM without cytotoxicity against human fetal lung fibroblast MRC-5 cells (IC > 25 μM).
An antimalarial lipopeptide, ikoamide, was isolated from an Okeania sp. marine cyanobacterium. Its gross structure was established by spectroscopic analyses, and the absolute configuration was clarified based on a combination of chiralphase HPLC analyses, spectroscopic analyses, and derivatization reactions. Ikoamide showed strong antimalarial activity with an IC 50 value of 0.14 μM without cytotoxicity against human cancer cell lines at 10 μM.
Irijimasides A–E (1–5),
a series of new 14-membered macrolide glycosides, were isolated from
a marine cyanobacterium collected in Okinawa. The gross structures
of 1–5 were established by spectroscopic
analysis, including 2D NMR, while absolute stereostructures were determined
based on NOESY spectra, chemical derivatization, and ECD data. All
five macrolides suppressed receptor activator of nuclear factor-κB
ligand (RANKL)-induced tartrate-resistant acid phosphatase (TRAP)
activity in mouse RAW264 macrophage cells, indicating that these compounds
inhibit osteoclast formation.
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