Final solution on the long-standing structural arguments on the C-3 stereochemistries of three glucoindole alkaloids: Palicoside, dolichantoside, and isodolichantoside — through chemical conversions and spectroscopic studies
Three natural strictosidine/vincoside-class glucoindole alkaloids have been chemically correlated with strictosidinic acid possessing a rigorously established stereostructure. The C-3 stereochemistry of palicoside, dolichantoside, and isodolichantoside has been firmly proved to be (S), (S), and (R), respectively.
The enzymatic glucose cleavage of palicoside revealed the biosynthetic pathway to akagerine, whereas the conversion of dolichantoside led to a new quaternary heteroyohimbinealkaloid named N(b)-methyl-21-beta-hydroxy-mayumbine. The hypothetical models of reactions occurring after the conversion of both substrates are proposed. Dolichantoside and palicoside, as well as Strychnos mellodora stem bark