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Tabernaelegantinines C and D, isolated from the root bark of Tabernaemontana elegans, have been shown by spectroscopic data and chemical correlation to be ‘dimer’ alkaloids composed of a dregamine unit and an isovoacangine unit connected through a linkage involving C(3) of the former and C(12′) or C(10′) of the latter, respectively. The isovoacangine unit of both compounds contains an extra cyano-group at C(3′) and the configuration at this centre is (S).

The Swern reaction of 3-alkyl-4-hydroxycoumarins affords in high yield α-chloro-α-alkyl-o-hydroxyacetophenone derivatives, resulting from the halogenodecarbonylation of the pyranone ring. On a model compound, other activators of DMSO (TFAA, P4O10, DCC, SO3–pyridine) gave mixtures of methylthiomethyl derivatives, accompanied by a dimeric product in the case of P4O10. The formation of the halogenated acetophenones and the dimeric product can be rationalized assuming the initial formation of a chromandionyl sulphonium salt, followed by nucleophilic displacement by the chloride counterion or by the unchanged 4-hydroxycoumarin. The resulting 3,3-disubstituted chromandiones are then hydrolytically decarboxylated during the aqueous work-up.

The absolute configuration (S) of the long-known indole alkaloid (+)-evodiamine (1) has been established by correlation with (S)-tryptohpan via(7S,13bS)- carboxyevodiamine (2).

The leaves of Ocotea acutangula(Mez) contain, in addition to the known (S)-(–)-pallidine (5) and its new derivative (S)-(–)-O-methylpallidine (6), the new 8,14-dihydromorphinandienone alkaloids (S)-(–)pallidinine (7) and (S)-(–)-O-methylpallidinine (8) which possess a B/Ctrans-junction.