Indolalkaloide aus den Blättern von <i>Hedranthera barteri (Hook. f.) Pichon</i>. 146. Mitteilung über Alkaloide

Abstract

Abstract From the leaves of the West African plant ( Apocynaceae Hedranthera barteri ) has been isolated the phenolic (−)‐desmethyl‐vobtusine ( 3 ), alongside the already known bisindole alkaloids (−)‐goziline ( 1 ) and (−)‐vobtusine ( 2 ). The new alkaloid 3 has been spectroscopically characterised and correlated with (−)‐vobtusine ( 2 ). Furthermore, the ‘monomeric’ alkaloids (−)‐hedrantherine ( 4 ) and (−)‐17‐hydroxy‐hedran‐therine ( 5 ) were found in the leaves of H. barteri . Both of these alkaloids contain a cyclic semiacetal group. These bases and their derivatives possessing an unchanged β‐anilinoacrylester group show, in the mass spectrometer, the same characteristic fragmentation as vincadifformine ( 11 ), whilst their 2,3‐dihydroderivatives bear more of a resemblance to aspidospermine. From the strongly negative Cotton effect of 4 and 22 at 300–350 nm follows the absolute configuration in these bases of centre 12. Hedrantherine ( 4 ) represents the lower half of the bisindole type of vobtusine bases. The upper half has previously been encountered in form of the alkaloid beninine in the rootbark of H. barteri .