CYCLOPEPTIDE ALKALOIDS FROM ANTIDESMA-MONTANA

Two cyclopeptide alkaloids, AM-1 and AM-2, were isolated from the leaves and terminal branches of Antidesma montana. By spectroscopic methods AM-1 was shown to be 2-dimethylamino-3-phenyl-N-[3-(1-methylethyl)-742-methylpropyl)-5,8-dioxo-2-oxa-6,9-diazobicyclo[omega.2.2]hexadeca-10,12,14,15-tetraene-4-yl]propanamide and AM-2 to be 2-dimethylamino-3-phenyl-N-[3-(1-methylethyl)-7-(2-methylpropyl)-5,8-dioxo-2-oxa-6,9-diazo-bicyclo[omega.2.2]hexadeca-12,14,15-triene-4-yl]propanamide. These structures have previously been proposed for myrianthine B and aralionine B, respectively, but the reported physical properties differ markedly from those of AM-1 and AM-2. However, direct comparison of AM-1 with an authentic sample of myrianthine B confirmed their identity. A GC method was used to establish the chirality of the isoleucine in AM-1, AM-2 and myrianthine B as L. The chirality of N,N-dimethylphenylalanine in AM-1 and myrianthine B and of N-methylphenylalanine in AM-2 was also found to be L.