1,2,3,6-Tetrahydropyridine-3-carboxylic acid (3), the β, γ-unsaturated derivative of the GABA uptake inhibitor nipecotic acid (1), has been synthesized by deconjugation via the dilithium salt of the N-t-butyloxycarbonyl-protected intermediate (6). Substitution of the intermediate with alkylating agents or an aldehyde gave predominantly a-alkylated products but chlorination with N-chlorosuccinimide provided a route to the γ-substituted unsaturated amino acid (13a).

Die Reaktion des Cyclopropens (I) mit Eisen(III)‐chlorid liefert in siedendem Ethanol das Cyclopropen (II) und ein Indenon (III).

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Der Ester (I) wird in die Säure (II) übergeführt, aus der das Dianion (III) in situ hergestellt wird.