Liquid-liquid extraction and liquid chromatographic studies on interactions of inorganic anions with coordinatively unsaturated copper(II) complexes of heterocyclic azo compounds.

The interactions between Cu(II) complexes with heterocyclic azo compounds and several anions were studied by equilibrium analysis of ion-pair extraction, RP-HPLC of metal complexes, and ion chromatography of anions on an ODS column coated with Cu(II) complexes of the long alkyl derivatives. Both ion-pair extraction and HPLC studies demonstrated that a dicationic complex with 8-(3,5-dibromo-2-pyridylazo)-5-aminoquinoline interacted with anions stronger than a monocationic complex with 2-(2-pyridylazo)methylphenol. Anions were more retained on the column coated with dicationic Cu(II) complex. Such differences were quantitatively ascribed to the first ion-pair formation of the dicationic complex giving a monocationic species.

A concise synthesis of spirotryprostatin A.

The preparation of two new synthons, 2,5- and 2,6-dibromotryptophan esters, and their use in diastereoselective intramolecular N-acyliminium ion spirocyclization methodology for the rapid construction of spirotryprostatin A and analogues are described.

Preparation and synthetic applications of 2-halotryptamines: synthesis of elacomine and isoelacomine.

The preparation of 2-halotryptamines from tryptamine is described. New stereoselective intramolecular iminium ion spirocyclization methodology for the construction of spiro[pyrrolidine-3,3'-oxindoles] is outlined in synthetic studies of elacomine (1) and isoelacomine (2). [reaction: see text]

Synthesis of marine sponge bisindole alkaloids dihydrohamacanthins.

[structure: see text] A convergent synthesis of the marine sponge bisindole alkaloids dihydrohamacanthins is described. The synthesis centers on the construction of 3,5- and 3,6-linked pyrazinones and their reduction to the requisite piperazinones with sodium cyanoborohydride.