41 Kauluamine : インドネシア産スポンジPrianos sp.が生産する新奇manzamineダイマー(口頭発表の部)

抄録

The manzamines, first described by Higa and coworkers in 1986, are an intriguing group of marine alkaloids, characterized by a fused and bridged tetra- or pentacyclic ring system that is joined to a tryptophan-derived β-carboline. The biogenesis of the manzamines was initially baffling. Baldwin's ingenious suggestion of an intramolecular Diels-Alder reaction in a macrocyclic bisdihydropyridine is eminently reasonable. We now present the structure of kauluamine (1), which is an unsymmetrical manzamine dimer, thus adding yet another level of complexity to this fascinating group of alkaloids. The dichloromethane-ethanol (5:1)-soluble part of the ethanol extracts of an Indonesian sponge, Prianos sp., was subjected to an Al_2O_3 column followed by HSCCC to give kauluamine (1) as an unstable solid of composition C_<72>H_<94>N_8O_3. Structural elucidation proved difficult because of instability and severe overlapping of signals in ^<13>C and ^1H NMR spectra. Many of these difficulties could be overcome by formation of a monoacetate (2, C_<74>H_<96>N_8O_4). 2D NMR techniques, especially HOHAHA and HMQC-HOHAHA experiments, made structural elucidation feasible.