Abstract
Young roots of wheat, barley, and sorghum, as well as methyl jasmonate pretreated rice seedlings, undergo an unprecedented allene oxide synthase pathway targeted to previously unknown oxylipins 1-3. These Favorskii-type products, (4Z)-2-pentyl-4-tridecene-1,13-dioic acid (1), (2'Z)-2-(2'-octenyl)-decane-1,10-dioic acid (2), and (2'Z,5'Z)-2-(2',5'-octadienyl)-decane-1,10-dioic acid (3), have a carboxy function at the side chain, as revealed by their MS and NMR spectral data. Compounds 1-3 were the major oxylipins detected, along with the related α-ketols. Products 1-3 were biosynthesized from (9Z,11E,13S)-13-hydroperoxy-9,11-octadecadienoic acid, (9S,10E,12Z)-9-hydroperoxy-10,12-octadecadienoic acid (9-HPOD), and (9S,10E,12Z,15Z)-9-hydroperoxy-10,12,15-octadecatrienoic acid, respectively, via the corresponding allene oxides and cyclopropanones. The data indicate that conversion of the allene oxide into the cyclopropanone is controlled by soluble cyclase. The short-lived cyclopropanones are hydrolyzed to products 1-3. The collective name "graminoxins" has been ascribed to oxylipins 1-3.