			Home About us Contact

Natural Alkaloid (natural + alkaloid)

Distribution by Scientific Domains

Chemistry	70%
Medical Sciences	30%

Distribution within Chemistry

Organic Chemistry	57%
General & Introductory Chemistry	28%

Selected Abstracts

Natural alkaloids and synthetic relatives as chiral templates of the Orito's reaction

CHIRALITY, Issue 1 2010
Emília Tálas
Abstract The enantioselective hydrogenation of methyl or ethyl pyruvate over cinchona-platinum catalyst system (Orito's reaction) is one of the most intensively studied heterogeneous catalytic asymmetric hydrogenation reactions. Studies aiming at systematic changes of the chiral template have played a crucial role in creating hypotheses for the mechanism of Orito's reaction. It is very important to clarify which structural unit of the alkaloid takes part in the enantiodifferentiation, and learn about the role of the different structural units of chiral templates. In this article, we made an attempt to describe the behavior of natural alkaloids, their synthetic derivatives, and analogues as chiral templates in the heterogeneous catalytic asymmetric hydrogenation of activated ketones. Chirality, 2010. © 2009 Wiley-Liss, Inc. [source]

Thaliporphine protects ischemic and ischemic-reperfused rat hearts via an NO-dependent mechanism

DRUG DEVELOPMENT RESEARCH, Issue 3 2001
Li-Man Hung
Abstract In ischemia or ischemia-reperfusion (I/R), nitric oxide (NO) can potentially exert several beneficial effects. Thaliporphine, a natural alkaloid with Ca2+ channel-activating and Na+/K+ channel-blocking activities, increased NO levels and exerted cardioprotective action in ischemic or I/R rats. The role of NO in the cardioprotective actions of thaliporphine was assessed. The severity of rhythm disturbances and mortality in anesthetized rats with either coronary artery occlusion for 30 min, or 5 min followed by 30-min reperfusion, were monitored and compared in thaliporphine- vs. placebo-treated groups. Thaliporphine treatment significantly increased NO and decreased lactate dehydrogenase (LDH) levels in the blood during the end period of ischemia or I/R. These changes in NO and LDH levels by thaliporphine were associated with a reduction in the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) during ischemic or I/R period. The mortality of animals was also completely prevented by 1 × 10,8 moles/kg of thaliporphine. In animals subjected to 4 h of left coronary artery occlusion, 1 × 10,7 moles/kg of thaliporphine dramatic reduced cardiac infarct zone from 46 ± 6% to 7.1 ± 1.9%. Inhibition of NO synthesis with 3.7 × 10,6 moles/kg of N, -nitro-L-arginine methyl ester (L-NAME) abolished the beneficial effects of thaliporphine during 30 min or 4 h myocardial ischemia. However, the antiarrhythmic activity and mortality reduction efficacy of thaliporphine during reperfusion after 5 min of ischemia was only partially antagonized by L-NAME. These results showed that thaliporphine efficiently exerted the cardioprotections either in acute or prolonged coronary artery occlusion or occlusion-reperfusion situations. The fact that thaliporphine induced cardioprotective effects were abrogated by L-NAME indicates that NO is an important mediator for the cardioprotective effects of thaliporphine in acute or prolonged ischemia, whereas antioxidant activities may contribute to the protection of I/R injury. Drug Dev. Res. 52:446,453, 2001. © 2001 Wiley-Liss, Inc. [source]

Synthesis and Comparative Glycosidase Inhibitory Properties of Reducing Castanospermine Analogues

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2005
Paula Díaz Pérez
Abstract The feasibility of the intramolecular nucleophilic addition of the nitrogen atom in cyclic (thio)carbamates with a pseudo- C -nucleoside structure to the masked carbonyl group in aldose precursors in the synthesis of reducing (i.e., 5-hydroxy)6-oxaindolizidine frameworks is illustrated by the preparation of the 6- epi, 7- epi, 8- epi and 6,8a-di- epi diastereomers of the potent glycosidase inhibitor (+)-castanospermine. In all cases, the increased anomeric effect caused by the high sp2 character of the pseudoamide-type nitrogen atom resulted in the pseudoanomeric hydroxy group being anchored in an axial orientation in aqueous solution, as in the aglycons in ,-glycosides. These analogs of the natural alkaloid showed a higher selectivity in the inhibition of ,-glucosidases. Structure/glycosidase inhibitory activity studies indicated that inversion of any hydroxy group resulted in a dramatic decrease in the inhibition potency, confirming the critical importance of a correct hydroxylation profile. In the case of (+)-8- epi -6-oxacastanospermine derivatives, with a hydroxylation profile with a structural complementarity to that of D -galactose, a moderate but very selective inhibition of ,-galactosidase was observed, supporting the importance of a defined configuration at pseudoanomeric centres for anomeric specificity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Synthesis of the Spermidine Alkaloids (,)-(2R,3R)- and (,)-(2R,3S)-3-Hydroxycelacinnine: Macrocyclization with Oxirane-Ring Opening and Inversion via Cyclic Sulfamidates

HELVETICA CHIMICA ACTA, Issue 6 2003
Nikolai
The two epimers (,)- 1a and (,)- 1b of the macrocyclic lactam alkaloid 3-hydroxycelacinnine with the (2R,3R) and (2R,3S) absolute configurations, respectively, were synthesized by an alternative route involving macrocyclization with the regio- and stereoselective oxirane-ring opening by the terminal amino group (Schemes,2 and 6). Properly N -protected chiral trans -oxirane precursors provided (2R,3R)-macrocycles after a one-pot deprotection-macrocyclization step under moderate dilution (0.005,0.01M). The best yields (65,85%) were achieved with trifluoroacetyl protection. Macrocyclization of the corresponding cis -oxiranes was unsuccessful for steric reasons. Inversion at OHC(3) via nucleophilic displacement of the cyclic sulfamidate derivative with NaNO2 led to (2R,3S)-macrocycles. The synthesized (,)-(2R,3S)-3-hydroxycelacinnine ((,)- 1b) was identical to the natural alkaloid. [source]

Homoharringtonine, omacetaxine mepesuccinate, and chronic myeloid leukemia circa 2009

CANCER, Issue 23 2009
Alfonso Quintás-Cardama MD
Abstract Homoharringtonine (HHT) is a natural alkaloid that is obtained from various Cephalotaxus species. The mechanism of action by which HHT exerts its antitumor activity is through inhibition of protein synthesis and promotion of apoptosis. In the 1990s, HHT proved to be significantly active as salvage therapy for patients with chronic myeloid leukemia (CML) after failure on interferon,, therapy. However, the remarkable success of imatinib mesylate in the treatment of CML relegated HHT to oblivion. The development of omacetaxine mepesuccinate, a subcutaneously bioavailable semisynthetic form of HHT, and its activity in imatinib-resistant CML has established this agent for the second time as a valuable option in the management of this disease. Preliminary results appear to support the use of this agent for patients who have imatinib-resistant CML, including those who carry the tyrosine kinase inhibitor-insensitive mutation that exchanges the amino acids threonine and isoleucine at position 315 (the T315I mutation). In this article, the authors discuss the current data on omacetaxine and the prospects of this agent to be integrated into the state-of-the-art treatment algorithms for CML. Cancer 2009. © 2009 American Cancer Society. [source]

Molecular Basis for ,-Glucosidase Inhibition by Ring-Modified Calystegine Analogues

CHEMBIOCHEM, Issue 16 2008
Matilde Aguilar
Neutral calystegine B2analogues, such as the 1-deoxy-6-oxa- N -(N, -octyl)thiocarbamoyl derivative, proved to be more potent ,-glucosidase inhibitors than the natural alkaloid. Structural studies of the complex with a clan GH-A ,-glucosidase from Thermotoga maritima showed a binding mode markedly different from that of the parent compound. [source]

ChemInform Abstract: Organocatalyzed Enantioselective One-Pot Three-Component Access to Indoloquinolizidines by a Michael Addition,Pictet,Spengler Sequence.

CHEMINFORM, Issue 36 2010
Xiaoyu Wu
Abstract The title method is potentially useful in combinatorial library construction and the synthesis of natural alkaloids. [source]

Accidental mydriasis from exposure to Angel's trumpet (Datura suaveolens)

ACTA OPHTHALMOLOGICA, Issue 3 2002
Ulf Havelius
ABSTRACT. Purpose:, To report clinical findings after accidental instillation into the eye of sap from Angel's trumpet (Datura suaveolens). Methods:, We report findings on seven patients who developed sudden onset of unilateral mydriasis. At least three of them also had ipsilateral cycloplegia and one developed transient tachycardia. Results:, The symptoms evolved after ocular exposure to sap from Angel's trumpet, a plant containing natural alkaloids with parasympatholytic properties. Six patients were initially unaware of the cause of their symptoms. In these cases, patient history revealed recent contact with Angel's trumpet. Conclusion:, Accidental ocular instillation of sap from Angel's trumpet should be noted as a cause of sudden onset of mydriasis in otherwise unaffected patients and also of general symptoms like tachycardia. [source]

RhI -Catalyzed Cycloisomerization of Vinyl Bicyclopropyl Compounds to Azabicyclo[3.2.2]nona-2,8-dienes

CHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2010
Young Kim
Important class: Nitrogen-containing heterobicycles are an important structural motif ubiquitous in natural alkaloids. We found that azabicyclo[3.2.2]nona-2,8-dienes can be synthesized from vinyl bicyclopropropyl derivatives in the presence of a RhI catalyst (see scheme). Syntheses of such compounds and an investigation into the reaction mechanism through DFT calculations are presented. [source]