A new alkaloid of Strychnos. The ocurrence of 11-methoxy-diaboline in Strychnos romeu-belenii Krukoff and Barneby
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From the stem bark of Strychnos romeu-belenii Krukoff and Barneby, a Longaniacea of South America, a new indolinic alkaloid has been isolated to which the structure of 11-,11-methoxy-diaboline(I) has been assigned on the basis of UV, IR, NMR, ORD and MS data. The structure was confirmed by converting(I) into α-colubrine(II) (11-methoxy-strychnine) through the N-deacetyl-derivative(III) (11-methoxy-Wieland-Gumlich aldehyde). (I) by acetylation gives the isomer C-17 of condensamine (IV) for which we propose the name isocondensamine(v). In addition, 11-methoxy-Wieland-Gumlich aldehyde(III) yields on heating with acetic acid and sodium acetate the dimeric 11,11'-dimethoxy-caracurine v (vi).