Ipobscurines C and D: macrolactam-type indole alkaloids from the seeds of Ipomoea obscura.
Separation of the methanolic seed extract of Ipomoea obscura afforded five indole alkaloids, three of them (ipobscurines B-D) being new natural products of a unique structural type characterized as serotonin hydroxycinnamic acid amide-type conjugates with a second phenylpropanoid moiety forming an ether with the 5-OH position of the indole nucleus. Due to an oxidative phenolic coupling between the two phenylpropanoid moieties of the supposed precursor ipobscurine B two 21-membered macrolactams with a phenol ether partial structure are formed: the trans-cis isomers ipobscurines C and D. Their structures were established on the basis of spectral data. Moreover, total synthesis of the racemic erythro- and threo-ipobscurine B 4',4"-dimethyl ethers and the comparison with the corresponding derivative of natural (-)-ipobscurine B proved an erythro configuration of the latter.
Jenett-Siems
Kristina
K
Institut für Pharmazie (Pharmazeutische Biologie), Freie Universität Berlin, Königin-Luise-Str 2-4, D-14195 Berlin, Germany.
Weigl
Robert
R
Kaloga
Macki
M
Schulz
Jutta
J
Eich
Eckart
E
D002851:Chromatography, High Pressure Liquid; D026121:Indole Alkaloids / Q000737:chemistry* / Q000302:isolation & purification; D027741:Ipomoea / Q000737:chemistry*; D007769:Lactams / Q000737:chemistry* / Q000302:isolation & purification; D019906:Nuclear Magnetic Resonance, Biomolecular; D012639:Seeds / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013237:Stereoisomerism
D026121:Indole Alkaloids; D007769:Lactams; C474272:ipobscurine C; C474273:ipobscurine D