Antagonistic alkaloids

Muscarinic Acetylcholine receptor (mACh-R) — antagonists Alkaloid Atropine (= d,l-Hyoscamine Tropine ( )-tropate ester) (racemate of hyoscamine)... 

Olofson and Martz have developed numerous applications of ACE-CI to the N-dealkylation of significant tertiary amines, especially in the field of analgesics and narcotic antagonists alkaloids, for example in a brilliant synthesis of Nalbuphine from Oxycodone in 69 % overall yield (Ref. 191). The scope and limitations of ACE-CI as a new reagent for the selective, high-yield N-dealkylation of tertiary amines will be examined in section 4-5 of voi. 2. 

Alkaloids are heterocyclic basic compounds and widespread in plants. Many of them have specific targets in organisms. For example, the alkaloids atropine and scopolamine of Belladonna are specific antagonists at muscarinic receptors. 

Bicuculline is a competitive antagonist at the GABAa receptor. It is a plant alkaloid. 

Curare is a generic term for various South American arrow poisons. Curare has been used for centuries by the Indians along the Amazon and Orinoco rivers for immobilizing and paralyzing wild animals used for food. Preparations of curare are derived from Strychnos species, which contain quaternary neuromuscular alkaloids like tubocurarine. Tubocurarine is a potent antagonist at the nicotinic acetylcholine receptor. 

The most widely used emetic is syrup of ipecac, containing the alkaloids, emetine and cq haeline. Emetine induces vomiting by activation of sensory neurons in the vagus and sympathetic nerves to the stomach and centrally in the medulla, possibly at the CTZ. The release of serotonin and SP may be involved as 5-HT3 and NKi receptor antagonists prevent emesis induced... 

Lobeline. The alkaloid lobehne, whose mechanism of action in unclear but that appears to have dopamine reuptake blockade and nicotinic receptor antagonist properties (Dwoskin and Crooks 2002), was evaluated in a double-bhnd, randomized, placebo-controUed, multicenter trial involving 180 ciga-... 

Phthalideisoquinoline alkaloids have been reviewed (1,2,176-179) and compiled (180). Because of the potential usefulness of phthalideisoquinoline alakloids such as bicuculline, a competitive antagonist of y-aminobutyric acid, many synthetic methods for these alkaloids have been developed. Several attractive transformations from protoberberines have also been reported. 

Analgesic and Narcotic Antagonist Activity of Some Hasubanan Alkaloids in Mice"... 

Zhao XY, Wang Y, Li Y, et al. Songorine, a diterpenoid alkaloid of the genus Aconitum, is a novel GABAa receptor antagonist in rat brain. Neurosci Lett 2003 337 33-36. 

Rhena-/3-ketoimine derivatives of several selected 2-ethylamino compounds have been prepared (36). These amines include 2-chloroethyl-amine (a DNA-alkylating reagent), cystamine ( a heparin antagonist), histamine (a potent vasodilator), tryptamine and O-methylserotonin (two indole alkaloids), and 0,0-dimethyldopamine (an adrenergic drug derivative). 

Histamine-receptor Antagonists Serotonin agonists Serotonin antagonists Ergot alkaloids... 

There are two types of pharmaceutically important derivatives (a) Compounds with a hydroxyl substituent at position 14, such as in oxycodone and the antagonists naloxone and naltrexone, and (b) Diels-Alder adducts such as etorphine and buprenorphine, where the latter compounds are all derived from another opium alkaloid, (—)-thebaine (12) (Scheme 5.10). Because thebaine is a rather scarce alkaloid, several syntheses have been investigated. Quite recently, Australian scientists have been able to modify P. somniferum in such a way that thebaine is now a main alkaloid, so that it is becoming better available [28],... 

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