LAST STAGES IN THE BIOSYNTHESIS OF ANTIRRHINOSIDE

Feeding experiments with H-2-labelled precursors have now shown that t he last steps in the biosynthesis of antirrhinoside in Antirrhinum maj us involve an initial hydroxylation of the 6-position of 6,10-dideoxya ucubin to give linaride (10-deoxyaucubin), followed by epoxidation to give 10-deoxycatalpol (5-deoxyantirrhinoside) and finally hydroxylatio n of the 5-position to give antirrhinoside. 10-Deoxycatalpol was prepa red by epoxidation of 10-deoxyaucubin with H2O2/WO3. Additionally, the iridoid content of two other species of Antirrhinum, namely A. specio sum and A. sicculum was investigated. In the first of these 10-deoxcat alpol was isolated for the first time from a plant together with antir rhinoside, linaride (10-deoxyaucubin) and macfadienoside. Antirrhinum sicculum contained 5-glucosyl antirrhinoside as the main iridoid toget her with antirrhinoside and macfadienoside.