Ancistrocladinium A and B, the first N,C-coupled naphthyldihydroisoquinoline alkaloids, from a Congolese Ancistrocladus species
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(Chemical Equation Presented) 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 ΔG‡1 = 105.8 kJ mol-1 and ΔG‡2 = 105.7 kJ mol-1, respectively. In addition, the compounds were shown to have promising antileishmanial activities.
Original language | English |
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Journal | Journal of Organic Chemistry |
Volume | 71 |
Issue number | 25 |
Pages (from-to) | 9348-9356 |
Number of pages | 9 |
ISSN | 0022-3263 |
DOIs | |
Publication status | Published - 8 Dec 2006 |
ID: 232592889