Isolation of Spirastrellolides A and B from a Marine Sponge <i>Epipolasis</i> sp. and Their Cytotoxic Activities

Spirastrellolides A (<b>1</b>) and B (<b>3</b>) have been isolated as free acids from a marine sponge <i>Epipolasis</i> sp. collected in the East China Sea. These compounds had been isolated from the Caribbean marine sponge <i>Spirastrella coccinea</i> after conversion to the methyl ester. We examined the cytotoxic activities of <b>1</b> and <b>3</b> and found that the activities of the free acids are comparable to those of the corresponding methyl esters

Structure Revision of Poecillastrin C and the Absolute Configuration of the β‑Hydroxyaspartic Acid Residue

The planar structure of poecillastrin C (<b>1</b>) was revised through selective reduction of the ester carbon. The absolute configuration of the β-hydroxyaspartic acid (OHAsp) residue was determined to be d-<i>threo</i> by Marfey’s analysis. The acid hydrolysate of the reduction product of <b>1</b> liberated (2<i>R</i>,3<i>R</i>)-2-amino-3,4-dihydroxybutanoic acid, demonstrating that the β-carboxyl group in poecillastrin C was esterified. The structures of poecillastrins B–D and 73-deoxychondropsin A were also revised

Yakushinamides, Polyoxygenated Fatty Acid Amides That Inhibit HDACs and SIRTs, from the Marine Sponge <i>Theonella swinhoei</i>

Yakushinamides A (<b>1</b>) and B (<b>2</b>), prolyl amides of polyoxygenated fatty acids, have been isolated from the marine sponge <i>Theonella swinhoei</i> as inhibitors of HDACs and SIRTs. Their planar structures were determined by interpretation of the NMR data of the intact molecules and tandem FABMS data of the methanolysis products. For the assignment of the relative configurations of the three contiguous oxymethine carbons in <b>1</b> and <b>2</b>, Kishi’s universal NMR database was applied to the methanolysis products. During the assignments of relative configurations of the isolated 1-hydroxy-3-methyl moiety in <b>1</b> and the isolated 1-hydroxy-2-methyl moiety in <b>2</b>, we found diagnostic NMR features to distinguish each pair of diastereomers. The absolute configurations of <b>1</b> and <b>2</b> were determined by a combination of the modified Mosher’s method and Marfey’s method. Although the modified Mosher’s method was successfully applied to the methanolysis product of <b>1</b>, this method gave an ambiguous result at C-20 when applied to the methanolysis product of <b>2</b>, even after oxidative cleavage of the C-14 and C-15 bond

Poecillastrin H, a Chondropsin-Type Macrolide with a Conjugated Pentaene Moiety, from a <i>Characella</i> sp. Marine Sponge

Poecillastrin H (<b>1</b>), a chondropsin-type macrolide with a conjugated pentaene moiety, was isolated from the <i>Characella</i> sp. marine sponge. The planar structure of <b>1</b> was elucidated by analysis of spectroscopic data. The absolute configuration of the β-hydroxyaspartic acid residue (β-OHAsp) was determined to be d-<i>threo</i> by Marfey’s analysis, and the mode of lactone ring formation through the OHAsp residue was determined by chemical degradation. Poecillastrin H was extremely sensitive toward light and showed potent cytotoxic activity against 3Y1 cells with an IC₅₀ value of 4.1 nM