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Gephyrotoxin
Gephyrotoxin is a naturally occurring product that stems from the Colombian tropical frog '' Dendrobates histrionicus''. It is a member of the class of compounds known as histrionicotoxins. This alkaloid skin secretion was first isolated from the tropical frog in 1977 by Daly and his fellow workers. Biological uses This compound is a relatively non-toxic chemical. At first it showed activity as a slight muscarinic antagonist, but with recent studies it has showed other interesting neurological activities. Due to these new activities, many laboratories want to conduct future research on it. Due to this demand and the scarcity and lack of abundance of the tree frog the synthesis of this product is of much interest. Synthesis The first total synthesis of gephyrotoxin was performed by Kishi and his co-workers, here they prepped an intermediate from L-pyroglutamic acid Pyroglutamic acid (also known as PCA, 5-oxoproline, pidolic acid) is a ubiquitous but little studied natura ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dendrobates Histrionicus
The harlequin poison frog, also known as harlequin poison-dart frog (''Oophaga histrionica''), is a species of poison dart frog endemic to the Chocó Department, Chocó region of western Colombia. The frog is normally found on the ground of tropical rain forests, among fallen limbs or leaf litter. Some frogs traditionally classified as ''Oophaga histrionica'' were separated as new species in 2018. These are ''Oophaga anchicayensis'', ''Oophaga andresi'' and ''Oophaga solanensis''. Description The harlequin poison frog has an average snout–vent length of . The background coloration varies from light to dark brown, and there is usually a vivid spot on the dorsum. Life history The harlequin poison frog lives on the forest floor. The male calls from a low perch to advertise his presence and the female lays eggs among the leaf litter. When the eggs hatch, a parent transports the newly hatched tadpoles to a tiny water reservoir (often in the leaf, axil of a Bromeliaceae, bromeliad). T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Histrionicotoxin
Histrionicotoxins are a group of related toxins found in the skin of poison frogs from the family Dendrobatidae, notably ''Oophaga histrionica'' (formerly ''Dendrobates histrionicus''), which are native to Colombia. It is likely that, as with other poison frog alkaloids, histrionicotoxins are not manufactured by the amphibians, but absorbed from insects in their diet and stored in glands in their skin. They are notably less toxic than other alkaloids found in poison frogs, yet their distinct structure acts as a neurotoxin by non-competitive inhibition of nicotinic acetylcholine receptors. History The first record of histrionicotoxins dates to 1823 by Captain Charles Stuart Cochrane. Cochrane was exploring the tropical rainforests around Colombia and Panama. His reports mention tribes of Indians who used poison tipped arrows and blowgun darts for hunting and war. Upon further exploration, Cochrane found that these Indians extracted the poison from the skins of the poison dart frog, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muscarinic
Muscarinic acetylcholine receptors, or mAChRs, are acetylcholine receptors that form G protein-coupled receptor complexes in the cell membranes of certain neurons and other cells. They play several roles, including acting as the main end-receptor stimulated by acetylcholine released from postganglionic fibers in the parasympathetic nervous system. Muscarinic receptors are so named because they are more sensitive to muscarine than to nicotine. Their counterparts are nicotinic acetylcholine receptors (nAChRs), receptor ion channels that are also important in the autonomic nervous system. Many drugs and other substances (for example pilocarpine and scopolamine) manipulate these two distinct receptors by acting as selective agonists or antagonists. Function Acetylcholine (ACh) is a neurotransmitter found in the brain, neuromuscular junctions and the autonomic ganglia. Muscarinic receptors are used in the following roles: Recovery receptors ACh is always used as the neuro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Receptor Antagonist
A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of receptor proteins.Pharmacology Guide: In vitro pharmacology: concentration-response curves " '' GlaxoWellcome.'' Retrieved on December 6, 2007. They are sometimes called blockers; examples include alpha blockers, |
Yoshito Kishi
is a Japanese chemist who is the Morris Loeb Professor of Chemistry at Harvard University. He is known for his contributions to the sciences of organic synthesis and total synthesis. Kishi was born in Nagoya, Japan and attended Nagoya University, where he obtained both his BS and PhD degrees. He was a postdoctoral research fellow at Harvard University where he worked with Robert Burns Woodward. From 1966 through 1974, he was a professor of chemistry at Nagoya University. Since 1974, Kishi has been a professor of chemistry at Harvard University. Kishi's research has focused on the total synthesis of complex natural products. The accomplishments of his research group include the total syntheses of palytoxin, mycolactones, halichondrins, saxitoxin, tetrodotoxin, geldanamycin, batrachotoxin and many others. Kishi has also contributed to the development of new chemical reactions including the Nozaki–Hiyama–Kishi reaction. Recognition *1999 Imperial Prize of the Japan Academ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyroglutamic Acid
Pyroglutamic acid (also known as PCA, 5-oxoproline, pidolic acid) is a ubiquitous but little studied natural amino acid derivative in which the free amino group of glutamic acid or glutamine cyclizes to form a lactam. The names of pyroglutamic acid conjugate base, anion, salts, and esters are pyroglutamate, 5-oxoprolinate, or pidolate. It is a metabolite in the glutathione cycle that is converted to glutamate by 5-oxoprolinase. Pyroglutamate is found in many proteins including bacteriorhodopsin. ''N''-terminal glutamic acid and glutamine residues can spontaneously cyclize to become pyroglutamate, or enzymatically converted by glutaminyl cyclases. This is one of several forms of blocked ''N''-termini which present a problem for ''N''-terminal sequencing using Edman chemistry, which requires a free primary amino group not present in pyroglutamic acid. The enzyme pyroglutamate aminopeptidase can restore a free ''N''-terminus by cleaving off the pyroglutamate residue. Pyroglutam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula (CH2)4NH. It is a cyclic secondary amine, also classified as a saturated heterocycle. It is a colourless liquid that is miscible with water and most organic solvents. It has a characteristic odor that has been described as "ammoniacal, fishy, shellfish-like". In addition to pyrrolidine itself, many substituted pyrrolidines are known. Production and synthesis Industrial production Pyrrolidine is prepared industrially by the reaction of 1,4-butanediol and ammonia at a temperature of 165–200 °C and a pressure of 17–21 MPa in the presence of a cobalt- and nickel oxide catalyst, which is supported on alumina. : The reaction is carried out in the liquid phase in a continuous tube- or tube bundle reactor, which is operated in the cycle gas method. The catalyst is arranged as a fixed-bed and the conversion is carried out in the downflow mode. The product is obtained after mu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quinoline Alkaloids
Quinoline alkaloids are naturally occurring chemical compounds from the group of alkaloids, which are chemically derived from quinoline. Some quinoline alkaloids show antiseptic, convulsive or antineoplastic effects. Examples Alkaloids with a quinoline partial structure are widespread and are usually further subdivided according to their occurrence and biogenetic origin. Among the quinoline alkaloids are the cinchona alkaloids quinine and quinidine, which are important due to their therapeutic potential, furthermore cinchonine and cinchonidine, as well as some furoquinoline alkaloids and acridine alkaloids. Strychnine and brucine, alkaloids of the nux vomica, which have a hydrogenated quinoline system, are also counted among the quinoline alkaloids. Also nitramarine (1-(2-quinolinyl)-β-carboline) belongs to the quinoline alkaloids. File:Chinin.svg, Qinine File:Chinidin.svg, Qinidine File:Cinchonidin.svg, Cinchonidine File:Strychnine2.svg, Strychnine Occurrence The quin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkyne Derivatives
\ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula . Alkynes are traditionally known as acetylenes, although the name ''acetylene'' also refers specifically to , known formally as ethyne using IUPAC nomenclature. Like other hydrocarbons, alkynes are generally hydrophobic. Structure and bonding In acetylene, the H–C≡C bond angles are 180°. By virtue of this bond angle, alkynes are rod-like. Correspondingly, cyclic alkynes are rare. Benzyne cannot be isolated. The C≡C bond distance of 121 picometers is much shorter than the C=C distance in alkenes (134 pm) or the C–C bond in alkanes (153 pm). : The triple bond is very strong with a bond strength of 839 kJ/mol. The sigma bond contributes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkene Derivatives
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, and Biological Chemistry'. 1232 pages. Two general types of monoalkenes are distinguished: terminal and internal. Also called α-olefins, terminal alkenes are more useful. However, the International Union of Pure and Applied Chemistry (IUPAC) recommends using the name "alkene" only for acyclic hydrocarbons with just one double bond; alkadiene, alkatriene, etc., or polyene for acyclic hydrocarbons with two or more double bonds; cycloalkene, cycloalkadiene, etc. for cyclic ones; and "olefin" for the general class – cyclic or acyclic, with one or more double bonds. Acyclic alkenes, with only one double bond and no other functional groups (also known as mono-enes) form a homologous series of hydrocarbons with the general formula with '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
