Three new -isocrotonyl-3-hydroxybutyric acid congeners produced by a sea anemone-derived marine bacterium of the genus .

Liquid cultures of sp. SI9, isolated from the outer tissue of the sea anemone , was found to produce three new -isocrotonyl-3-hydroxybutyric acid derivatives, -isocrotonyl-3-hydroxypentanoic acid (), -isocrotonyl-3-hydroxyhexanoic acid (), and -()-2-hexenoyl-3-hydroxybutyric acid (), together with the known -isocrotonyl-3-hydroxybutyric acid (). The structures of - were established by NMR spectroscopy and mass spectrometry, coupled with anisotropy-based chiral analysis, revealing the same -configuration for all congeners -. The compounds - were weakly growth-inhibitory against a marine fish ulcer pathogenic bacterium, NBRC16015. Structural similarities among -, the -isocrotonylated 3-hydroxybutyrate oligomers , and microbial biopolymer polyhydroxyalkanoates (PHA) suggest the presence of a common biosynthetic machinery, and hence a possible dehydrative modification at the hydroxy terminus of PHA.