Absolute stereostructures and syntheses of saussureamines A, B, C, D and E, amino acid-sesquiterpene conjugates with gastroprotective effect, from the roots of Saussurea lappa

From the methanolic extract of the dried roots of Saussurea lappa Clarke, S aussureae Radix, five amino acid-sesquiterpene conjugates, saussureamines A , B, C, D and E, were isolated together with a lignan glycoside, (-)-masson iresinol 4 "-O-beta-D-glucopyranoside. Their stereostructures were determin ed on the basis of chemical and physicochemical evidence. In addition, saus sureamines and the related amino acid-sesquiterpene conjugates were synthes ized using a Michael type addition reaction of amino acid to the alpha-meth ylene-gamma-lactone moiety of sesquiterpenes. Saussureamines A, B and C, co stunolide and dehydrocostus lactone showed a gastroprotective effect on aci dified ethanol-induced gastric mucosal lesions in rats. Saussureamines A al so exhibited an inhibitory effect on gastric mucosal lesions induced by wat er-immersion stress in mice. (C) 2000 Elsevier Science Ltd. All rights rese rved.