The Biosynthesis of the Ipecac Alkaloids and of Ipecoside and Alangiside

Abstract

The synthesis of (1–³H, 3–¹⁴C)–(1α)–desacetylisoipecoside and –(1β)–desacetylipecoside is described. Feeding experiments with the pure epimers showed that in contrast to previous assumptions, desacetylisoipecoside is the true precursor for the ipecac alkaloids (cephaeline and emetine) in both Cephaelis and Alangium. The 1β epimer, desacetylipecoside, is the precursor only of the alkaloidal glucosides, ipecoside and alangiside, both of which posses the β–configuration. A biosynthetic scheme for the formation of these compounds is proposed and the difference between this pathway and monoterpenoid indole alkaloid biosynthesis is discussed.

Key Word Index

Cephaelis ipecacuanha - Rubiaceae - Alangium lamarckii - Alangiaceae - Alangiside - Cephaeline - Emetine - Ipecoside - Biosynthesis of Monoterpenoid Isoquinoline Alkaloids