Bicyclic α,ω-dicarboxylic acid derivatives from a colonial tunicate of the family Polyclinidae

Antibacterial Bicyclic Fatty Acids from a Korean Colonial Tunicate Didemnum sp.

“…The molecular formula of 4 was identified as C 23 H 30 O 4 on the basis of the HRFABMS data of the [M + H] + ion at m / z 371.2209 (Δ − 0.8 mmu) and 13 C NMR data ( Table 2 ). Interpretation of the spectroscopic data of 4 revealed that the planar structure of 4 is a bicyclic fatty acid with octa-5, 7-dienoyl and methyl penta-2,4-dienoate moieties, the same with a previous reported fatty acid derivative, aplidic acid A [ 13 ] except for the geometry of the double bond between C-4 and C-5. The geometry for the Δ 4 double bond was determined Z geometry on the basis of the coupling constant between H-4 and H-5 ( J 4, 5 = 11.0 Hz).…”

“…These differences in the NMR spectra indicated the presence of a 2-phenethyl amide moiety in 2 instead of isobutyl amide as in 1 . The planar structure of 2 was elucidated as a bicyclic carboxylic acid with a 2-phenethyl amide from analysis of 1D and 2D NMR spectra for 2 , which was the same with the structure of previously reported 4 Z -aplidic acid B [ 13 ]. Further analysis of NOESY spectra for 2 revealed that relative configurations of 2 were 6 R *, 7 S *, 11 S *, and 14 R *, the same as those of 1 at every stereogenic center.…”

“…The structures of 1 – 5 were very similar to the bicyclic fatty acid derivatives isolated from colonial tunicates of the family Polyclinidae [ 12 , 13 ]. Especially, 2 and 4 were stereoisomers of 4 Z -aplidic acid B and aplidic acid A, respectively, reported by Bao et al [ 13 ].…”

“…Interpretation of 2D NMR data including COSY, HSQC and HMBC spectra revealed that two rings comprise a fused bicyclic system (2, 3, 3a, 4, 5, 7a-hexahydro-4, 5-disubstituted-1H-indene) of which substituted functional groups are an octa-5, 7-dienoyl and an N -isobutyl 2, 4-pentadienamide moieties ( Figure 2 ). The fused bicyclic carboxylic acids belonging to the class of aplidic acids [ 13 ] were previously reported, but aplidic acid with N -isobutyl 2, 4-pentadienamide moiety has not been reported. The COSY correlations between H-3′ and H-2′/H-4′/H-5′ suggested the presence of isobutyl functionality, which was also supported by the HMBC correlations from H-4′ (δ 0.92) to C-2′ (δ 48.1), C-3′ (29.8), and C-5′ (δ 20.6), and from H-5′ to C-2′, C-3′ and C-4′ (δ 20.6).…”

“…The diversity of natural products isolated from tunicates is attributed to their frequent hosting of bacterial symbionts [ 2 , 3 , 4 , 5 , 6 ]. These metabolites are known to exhibit antibacterial [ 7 , 8 , 9 ], antiviral [ 10 , 11 ], antitumor [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ], and farnesoid X receptor (FXR) antagonistic activities [ 20 ]. Tunicates have yielded two natural product-derived drugs, trabectedin [ 19 ] and plitidepsin (dehydrodidemnin B) [ 21 ], which has been used as an anticancer drug.…”