Xyloccensins Q–V, six new 8,9,30-phragmalin ortho ester antifeedants from the Chinese mangrove Xylocarpus granatum

Six new 8,9,30-phragmalin ortho esters, named xyloccensins Q–V (), have been isolated from the stem bark of a Chinese mangrove Xylocarpus granatum, and their structures were elucidated on the basis of spectroscopic data and chemical means. The absolute stereochemistry of these compounds and xyloccensins O–P (), revised as enantiomeric to all the phragmalins reported so far, was determined by application of the modified MTPA Mosher ester method and circular dichroism analysis. Both xyloccensins P and Q exhibited potent antifeedant activity against the third instar larvae of Mythimna separata (Walker) at a concentration of 500 ppm.