Ancistrocladinium A and B, the first N,C-coupled naphthyldihydroisoquinoline alkaloids, from a Congolese ancistrocladus species.
The isolation and structural elucidation of three novel-type naphthylisoquinoline alkaloids, ancistrocladinium A and B (the latter along with its atropisomer), from a Congolese Ancistrocladus species collected in the habitat Yeteto is reported. Their structures, including all stereochemical features, were elucidated by spectroscopic, chemical, and chiroptical methods. Ancistrocladinium A and B are the first N,C-coupled naphthyldihydroisoquinoline alkaloids found in nature, i.e., with an iminium-aryl axis. Although ancistrocladinium A, which is N,8'-coupled, is configurationally stable at this axis, ancistrocladinum B and its rotational isomer are based on a hitherto unprecedented N,6'-coupling type, with a slow rotation about the hetero biaryl axis at room temperature; they thus occur as a 46:54 mixture of two configurationally semistable atropo-diastereomers. For the isomerization of (P)-ancistrocladinium B to its (M)-diastereomer and for the opposite direction, the Gibbs free energies of activation were determined to be DeltaG double dagger1 = 105.8 kJ mol-1 and DeltaG double dagger2 = 105.7 kJ mol-1, respectively. In addition, the compounds were shown to have promising antileishmanial activities.
Bringmann
Gerhard
G
Institute of Organic Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany. bringman@chemie.uni-wuerzburg.de
Kajahn
Inga
I
Reichert
Matthias
M
Pedersen
Sarah E H
SE
Faber
Johan H
JH
Gulder
Tanja
T
Brun
Reto
R
Christensen
Søren B
SB
Ponte-Sucre
Alicia
A
Moll
Heidrun
H
Heubl
Günther
G
Mudogo
Virima
V
D029748:Caryophyllaceae / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D007546:Isoquinolines / Q000737:chemistry* / Q000302:isolation & purification; D009682:Magnetic Resonance Spectroscopy; D021241:Spectrometry, Mass, Electrospray Ionization
D007546:Isoquinolines; C522869:ancistrocladinium A; C522870:ancistrocladinium B