A novel alkaloid, cassiarin F (1), which showed potent antiplasmodial activity against Plasmodium falciparum In vitro, was isolated from the flowers of Cassia siamea, and Its structure was elucidated on the basis of 2D NMR analyses. A total synthesis of 1 was also achieved by employing the Suzuki coupling constructing biaryl unit, nucleophilic aromatic substitution, and Houben-Hoesch type ring construction as key steps.
Two new C-21 Daphniphyllum alkaloids, longeracinphyllins A (1) and B (2), have been isolated from the leaves of Daphniphyllum longeracemosum. Longeracinphyllin A (1) is a new daphnilongeranin B type alkaloid with a rearranged alpha,beta-unsaturated ketone group, and the structure is supported by X-ray crystal data. Longeracinphyllin B (2) is a new seco-10,17-daphnilongeranin B type alkaloid.
Three new Daphniphyllum alkaloids, daphnioldhanins A-C (1-3), along with four known ones, were isolated from the aerial parts of saplings of Daphniphyllum oldhami. The structures of these alkaloids were established by spectroscopic methods. The relative configuration of 1 was further confirmed by a single-crystal X-ray diffraction analysis. In addition, the (1)H and (13)C NMR data of the free base of daphmanidin A (4) were compared with its hydrochloric salt form.
Seven new bromotyrosine alkaloids Purpurealidin A, B, C, D, F, G, H and the known compounds Purealidin Q, Purpurealidin E, 16-Debromoaplysamine-4 and Purpuramine I have been isolated from the marine sponge Psammaplysilla purpurea. Their structure was elucidated on the basis of detailed 1D, 2D NMR and MS spectroscopic data. Purpurealidin B, 16-Debromoaplysamine-4 and Purpuramine I exhibited in vitro antimicrobial activities against E. coli, S. aureus, and V. cholerae. In addition, Purpurealidin B and 16-Debromoaplysamine-4 were also active against Shigella flexineri and Salmonella typhi while Purealidin Q was bactericidal only against Salmonella typhi. (C) 2004 Elsevier Ltd. All rights reserved.
Novel laudanosine dimers in which two laudanosine units are linked at C-2' via a two or three-carbon linker (alkane, alkene or alkyne) have been prepared using palladium-catalysed cross-coupling reactions (Mizoroki-Heck and Sonagashira reactions). In one example, a second three-carbon linker between the two isoquinoline N-atoms was also present leading to a novel macrocyclic ring system. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.
<jats:title>Abstract</jats:title><jats:p>Two new lycopodine alkaloids, (12<jats:italic>β</jats:italic>)‐12‐hydroxyhuperzine G (<jats:bold>1</jats:bold>) and (5<jats:italic>β</jats:italic>,6<jats:italic>β</jats:italic>,15<jats:italic>α</jats:italic>)‐15‐methyllycopodane‐5,6‐diol (<jats:bold>2</jats:bold>), were isolated from the whole plants of <jats:italic>Huperzia serrata</jats:italic>, together with six known compounds, huperzines A, B, and G, phlegmariurine B, (8<jats:italic>β</jats:italic>)‐8‐hydroxyphlegmariurine B, and lycoposerramine D. Their structures were elucidated on the basis of spectroscopic analysis, including HR‐ESI‐MS, <jats:sup>1</jats:sup>H‐ and <jats:sup>13</jats:sup>C‐NMR, DEPT, <jats:sup>1</jats:sup>H,<jats:sup>1</jats:sup>H‐COSY, HSQC, HMBC, and NOESY data.
Two new quinoldione alkaloids, methyl 2-(3-hydroxy-1-methyl-2,4-dioxo-1,2,3,4-tetrahydroquinolin-3-yl)acetate (1) and 3-hydroxy-1-methyl-3-(2-oxopropyl)quinoline-2,4(1H,3H)-dione (2), and two quinolinone alkaloids previously synthesized but first isolated as natural products, N-methylflindersine (3) and 4-hydroxy-3-methoxy-1-methyl-2(1H)-quinolinone (4), were isolated from the stem bark of Micromelum falcatum, together with the known N-methylswietenidine-B (5). Their structures were established mainly on the basis of 1D- and 2D-NMR techniques. All compounds were evaluated for toxicity towards brine shrimp larvae, and 3 showed strong toxicity with an LD(50) value of 1.39 microg/ml.
Crude MeOH extracts from the stem bark and leaves of a Panamanian specimen of Albizia adinocephala (Leguminosae) were found to inhibit the malarial enzyme plasmepsin II. Bioassay guided fractionation led to the isolation of two new bioactive spermine alkaloids, budmunchiamines L4 and L5. (C) 2002 Elsevier Science Ltd. All rights reserved.
