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Results for “Aspidosperma”

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PubMed2002

Intramolecular amidofuran cycloadditions across an indole pi-bond: an efficient approach to the aspidosperma and strychnos ABCE core.

[reaction: see text] The intramolecular Diels-Alder reaction between an amidofuran moiety tethered onto an indole component was examined as a strategy for the synthesis of Aspidosperma and Strychnos alkaloids. Furanyl carbamate 13 was acylated using the mixed anhydride 16 to provide amidofuran 12 in 68% yield. Further N-acylation of this indole furnished 17 in 88% yield. Cyclization precursors were prepared by removing the carbamate moiety followed by N-alkylation with the appropriate alkyl halides. Thermolysis of 25 provided the novel tetracyclic ketone 26 in 74% yield.

Alkaloids↗

PubMed2006

Formal synthesis of aspidosperma alkaloids via the intramolecular [3 + 2] cycloaddition of 2-azapentdienyllithiums.

[reaction: see text] A formal synthesis of the Aspidosperma alkaloids aspidospermidine, aspidospermine, and quebrachamine is reported through an efficient preparation of Stork's penultimate intermediate. The key step of the sequence involved an intramolecular [3 + 2] cycloaddition of the 2-azapentadienyllithium 21 formed in situ from the corresponding imine 1, which after N-alkylation of the resulting cycloadduct provided 2 in excellent yield. The synthesis represents a new disconnection of the classical tricyclic ketone used for appendage of the requisite indole.

Aspidosperma↗

PubMed2004

Anti-leishmanial activity of alkaloidal extract from Aspidosperma ramiflorum.

Infections due to protozoa of the genus Leishmania are a major worldwide health problem, with high endemicity in developing countries. The drugs of choice for the treatment of leishmaniasis are the pentavalent antimonials (SbV), which present renal and cardiac toxicity. Besides, the precise chemical structure and mechanism of action of these drugs are unknown up to date. In order to find new drugs against leishmaniasis, we have been studying extracts of Brazilian trees. In the present study, we have evaluated the effectiveness of an alkaloid extract of Aspidosperma ramiflorum Muell. Arg. (Apocynaceae), against the extracellular forms promastigotes of L. (L.) amazonensis and L. (V.) braziliensis. The alkaloid extract of A. ramiflorum was much more effective against L. (L.) amazonensis (LD50 < 47 microg/ml) than L. (V.) braziliensis. Based on these in vitro results against L. (L.) amazonensis new studies should be made to find the compounds with anti-leishmanial activity.

Alkaloids↗

PubMed2006

Antibacterial activity of indole alkaloids from Aspidosperma ramiflorum.

We evaluated the antibacterial activities of the crude methanol extract, fractions (I-V) obtained after acid-base extraction and pure compounds from the stem bark of Aspidosperma ramiflorum. The minimum inhibitory concentration (MIC) was determined by the microdilution technique in Mueller-Hinton broth. Inoculates were prepared in this medium from 24-h broth cultures of bacteria (10(7) CFU/mL). Microtiter plates were incubated at 37 masculineC and the MICs were recorded after 24 h of incubation. Two susceptibility endpoints were recorded for each isolate. The crude methanol extract presented moderate activity against the Gram-positive bacteria B. subtilis (MIC = 250 microg/mL) and S. aureus (MIC = 500 microg/mL), and was inactive against the Gram-negative bacteria E. coli and P. aeruginosa (MIC > 1000 microg/mL). Fractions I and II were inactive against standard strains at concentrations of < or =1000 microg/mL and fraction III displayed moderate antibacterial activity against B. subtilis (MIC = 500 microg/mL) and S. aureus (MIC = 250 microg/mL). Fraction IV showed high activity against B. subtilis and S. aureus (MIC = 15.6 microg/mL) and moderate activity against E. coli and P. aeruginosa (MIC = 250 microg/mL). Fraction V presented high activity against B. subtilis (MIC = 15.6 microg/mL) and S. aureus (MIC = 31.3 microg/mL) and was inactive against Gram-negative bacteria (MIC > 1000 microg/mL). Fractions III, IV and V were then submitted to bioassay-guided fractionation by silica gel column chromatography, yielding individual purified ramiflorines A and B. Both ramiflorines showed significant activity against S. aureus (MIC = 25 microg/mL) and E. faecalis (MIC = 50 microg/mL), with EC50 of 8 and 2.5 microg/mL for ramiflorines A and B, respectively, against S. aureus. These results are promising, showing that these compounds are biologically active against Gram-positive bacteria.

Anti-Bacterial Agents↗

PubMed1994

Isolation and biological activity of aspidospermine and quebrachamine from an Aspidosperma tree source.

The indolealkaloids aspidospermine and quebrachamine have been isolated in crystalline form by a relatively rapid fractionation from the extract of a powdered material designated "Quebracho" derived from an Aspidosperma tree species. We present a novel isocratic LC method that provides baseline resolution of these two compounds and of the structurally related yohimbine in less than 15 min. Gas chromatography-mass spectrometry was employed to identify these compounds as well as several minor derivatives of aspidospermine during and after the purification process. Aspidospermine and quebrachamine like yohimbine have been found to possess adrenergic blocking activities for a variety of urogenital tissues.

Alkaloids↗

PubMed1998

Synthesis of the Pentacyclic Skeleton of the Aspidosperma Alkaloids Using Rhodium Carbenoids as Reactive Intermediates.

A series of diazo amido keto esters prepared from N-alkenyl-substituted 3-carbalkoxy-2-piperidone derivatives was treated with rhodium(II) acetate. Attack of the amido carbonyl oxygen at the resultant rhodium carbenoid center produced a transient push-pull carbonyl ylide dipole which underwent an intramolecular dipolar cycloaddition reaction. A related annulation sequence was used to prepare the pentacyclic skeleton of the aspidosperma family of alkaloids. Synthesis of the required diazo imide was carried out from 3-carboxy-3-ethyl-2-piperidone and N-methyl-3-indoleacetic acid. Treatment of the diazo imide with rhodium(II) acetate afforded a transient 1,3-dipole which subsequently underwent cycloaddition across the indole pi-bond. The resulting cycloadduct is the consequence of endo cycloaddition with respect to the dipole which is fully in accord with the lowest energy transition state. The cycloadduct was converted in three steps into desacetoxy-4-oxo-6,7-dihydrovindorosine. The stereochemistry of the final product was established by a X-ray crystallographic study.

Journal Article↗

PubMed1999

Flower Structure and Reproductive Biology in Aspidosperma quebracho-blanco (Apocynaceae), a Tree Pollinated by Deceit.

Flower structure, attractants, breeding system, and visitors were studied in Aspidosperma quebracho-blanco, a South American mass-flowering tree with simple moth-pollinated flowers and without floral reward. Flowers are protandrous, having an initial male phase for 2 d. The pendulous and horizontal flower position and protandry prevent self-pollination. Although an inconspicuous annular floral nectary is located at the ovary base, nectar is not secreted. Nonstructural, extrafloral nectaries have been found on the external surface of the calyx and corolla, the first report of the kind for the family. Ants, wasps, flies, and beetles collect the extrafloral exudate composed of fructose, glucose, and sucrose. Experiments indicate that natural selfing (autogamy) and agamospermy are unlikely to occur (0% success), but artificial selfing indicates self-compatibility (70% success). A very low natural fruit to flower ratio (0.03) was obtained. Floral features and nocturnal opening indicate that these flowers would be pollinated by moths that nocturnally visit the species (Noctuidae, Pyraloidea) finding no floral reward. We suggest a nonmodel deception mechanism: providing the same cues as most moth flowers, this tree seems to be dependent upon sympatric rewarding plants that share the same pollinators.

Journal Article↗

PubMed1983

[A new quaternary alkaloid from Aspidosperma gilbertii].

The present work describes the structure determination of a new quaternary carbozol type alkaloid, isolated from Aspidosperma gilbertii: N,N-Dimethyltetrahydroellipticinium Hydroxyde.

Alkaloids↗

PubMed1963