Names | |||
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Preferred IUPAC name 2-Hydroxycyclohepta-2,4,6-trien-1-one | |||
Other names 2-Hydroxytropone; Purpurocatechol | |||
Identifiers | |||
3D model (JSmol) | |||
ChEBI | |||
ChEMBL | |||
ChemSpider | |||
ECHA InfoCard | 100.007.799 | ||
EC Number |
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KEGG | |||
MeSH | D014334 | ||
PubChem CID | |||
UNII | |||
CompTox Dashboard (EPA) | |||
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Properties | |||
C7H6O2 | |||
Molar mass | 122.12 g/mol | ||
Melting point | 50 to 52 °C (122 to 126 °F; 323 to 325 K) | ||
Boiling point | 80 to 84 °C (176 to 183 °F; 353 to 357 K) (0.1 mmHg) | ||
Acidity (pKa) | 6.89 (and -0.5 for conjugate acid) | ||
-61·10−6 cm3/mol | |||
Hazards | |||
GHS labelling: [2] | |||
Danger | |||
H314, H317, H410 | |||
P260, P261, P264, P272, P273, P280, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P333+P313, P363, P391, P405, P501 | |||
Flash point | 112 °C (234 °F; 385 K) | ||
Related compounds | |||
Related compounds | Hinokitiol (4-isopropyl-tropolone) | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Tropolone is an organic compound with the chemical formula C7H5(OH)O. It is a pale yellow solid that is soluble in organic solvents. The compound has been of interest to research chemists because of its unusual electronic structure and its role as a ligand precursor. Although not usually prepared from tropone, it can be viewed as its derivative with a hydroxyl group in the 2-position.
Many methods have been described for the synthesis of tropolone. [3] One involves bromination of 1,2-cycloheptanedione with N-bromosuccinimide followed by dehydrohalogenation at elevated temperatures, while another uses acyloin condensation of the ethyl ester of pimelic acid the acyloin again followed by oxidation by bromine. [4]
An alternate route is a [2+2] cycloaddition of cyclopentadiene with a ketene to give a bicyclo[3.2.0]heptyl structure, followed by hydrolysis and breakage of the fusion bond to give the single ring: [3]
Thy hydroxyl group of tropolone is acidic, having a pKa of 7, which is in between that of phenol (10) and benzoic acid (4). The increased acidity compared to phenol is due to resonance stabilization with the carbonyl group, as a vinylogous carboxylic acid. [4]
The compound readily undergoes O-alkylation to give cycloheptatrienyl derivatives, which in turn are versatile synthetic intermediates. [5] With metal cations, it undergoes deprotonation to form a bidentate ligand, such as in the Cu(O2C7H5)2 complex. [4]
The carbonyl group is also highly polarized, as common for tropones. There can be substantial hydrogen bonding between it and the hydroxyl group, leading to rapid tautomerization: the structure is symmetric on the NMR timescale. [6]
Around 200 naturally occurring tropolone derivatives have been isolated, mostly from plants and fungi. [7] [8] [9] [10] Tropolone compounds and their derivatives include dolabrins, dolabrinols, thujaplicins , thujaplicinols, stipitatic acid , stipitatonic acid, nootkatin, nootkatinol, puberulic acid , puberulonic acid, sepedonin, 4-acetyltropolone, pygmaein, isopygmaein, procein, chanootin, benzotropolones (such as purpurogallin , crocipodin, goupiolone A and B), theaflavin and derivatives bromotropolones, tropoisoquinolines and tropoloisoquinolines (such as grandirubrine, imerubrine, isoimerubrine, pareitropone, pareirubrine A and B), colchicine , colchicone and others. [11] Tropolone arises via a polyketide pathway, which affords a phenolic intermediate that undergoes ring expansion. [5]
They are especially found in specific plant species, such as Cupressaceae and Liliaceae families. [9] Tropolones are mostly abundant in the heartwood, leaves and bark of plants, thereby the essential oils are rich in various types of tropolones. The first natural tropolone derivatives were studied and purified in the mid-1930s and early-1940s. [12] Thuja plicata , Thujopsis dolabrata , Chamaecyparis obtusa , Chamaecyparis taiwanensis and Juniperus thurifera were in the list of trees from which the first tropolones were identified. The first synthetic tropolones were thujaplicins derived by Ralph Raphael. [13]
Name | Chemical structure | Natural sources |
---|---|---|
Tropolone | Pseudomonas lindbergii, Pseudomonas plantarii [14] [15] [16] and mushroom tyrosinase. [17] | |
Hinokitiol | Cupressaceae trees [18] | |
Stipitatic acid | Talaromyces stipitatus [19] | |
Colchicine | Colchicum autumnale , Gloriosa superba [20] |
Class | Examples | Main natural sources [11] [9] [21] [22] | Research directions [9] [23] [11] [24] [25] | Patented in products [9] [26] |
---|---|---|---|---|
Simple tropolones | Tropolone | Pseudomonas lindbergii, Pseudomonas plantarii | Antibacterial, antifungal, insecticidal, pesticidal, plant growth inhibition, anti-inflammatory, antioxidant, neuroprotection, anti-protease, anti-browning (anti-tyrosinase and anti-polyphenol oxidase), antineoplastic, chelating | - |
Dolabrins | β-dolabrin, α-dolabrinol | Caragana pygmaea , Cupressus goveniana , Cupressus abramsiana , Thujopsis dolabrata | Antibacterial, antifungal, insecticidal, pesticidal, plant growth inhibition, protease inhibition | Insect repellent, deodorant |
Thujaplicins | α-thujaplicin, β-thujaplicin (hinokitiol), γ-thujaplicin, thujaplicinol | Chamaecyparis obtusa , Thuja plicata , Thujopsis dolabrata , Juniperus cedrus , Cedrus atlantica , Cupressus lusitanica , Chamaecyparis lawsoniana , Chamaecyparis taiwanensis , Chamaecyparis thyoides , Cupressus arizonica , Cupressus macnabiana , Cupressus macrocarpa , Cupressus guadalupensis , Juniperus chinensis , Juniperus communis , Juniperus californica , Juniperus occidentalis , Juniperus oxycedrus , Juniperus sabina , Calocedrus decurrens , Calocedrus formosana , Platycladus orientalis , Thuja occidentalis , Thuja standishii , Tetraclinis articulata , Cattleya forbesii , Carya glabra | Antifungal, antibacterial, anti-browning (anti-tyrosinase), chelating, insecticidal, pesticidal, antimalarial, antiviral, anti-inflammatory, plant growth inhibition, anti-protease, antidiabetic, antineoplastic, chemosensitizing, antioxidant, neuroprotection, veterinary medicine | Insect repellent, deodorant, toothpaste, oral spray, skin and hair care, wood preservative, food additive, food packaging |
Sesquiterpene tropolones | Nootkatin, nootkatinol, nootkatol, nootkatene, valencene-13-ol, nootkastatin | Chamaecyparis nootkatensis , Grapefruit | Antifungal, anti-browning (anti-tyrosinase), insecticidal, fungicidal, antineoplastic | Insect repellents, flavor, perfumery |
Pygmaeins | Pygmaein, Isopygmaein | Caragana pygmaea , Cupressus goveniana , Cupressus abramsiana | - | - |
Benzotropolones | Purpurogallin, crocipodin, goupiolone A and B | Quercus species, Leccinum crocipodium , Goupia glabra | Antibacterial, plant growth inhibition, protease inhibition, antineoplastic, antimalarial, antioxidant, antiviral | Food additive |
Theaflavins | Theaflavin, theaflavic acid, theaflavate A and B | Camellia sinensis , Quercus species | Antibacterial, anti-inflammatory, antioxidant, antiviral, antidiabetic, chemosensitizing | - |
Tropoisoquinolines and tropoloisoquinolines | Grandirubrine, imerubrine, isoimerubrine, pareitropone, pareirubrine A and B | Cissampelos pareira , Abuta grandifolia | Antileukemic | - |
Tropone alkaloids | Colchicine, demecolcine | Colchicum autumnale , Gloriosa superba | Antimitotic, anti-inflammatory, anti-gout, plant breeding | Pharmaceutical drug |
Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure may also be termed alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen or sulfur. Rarer still, they may contain elements such as phosphorus, chlorine, and bromine.
In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl groups bonded directly to an aromatic hydrocarbon group. The simplest is phenol, C
6H
5OH. Phenolic compounds are classified as simple phenols or polyphenols based on the number of phenol units in the molecule.
L-Tyrosine or tyrosine or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Greek tyrós, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a functional group or side chain. While tyrosine is generally classified as a hydrophobic amino acid, it is more hydrophilic than phenylalanine. It is encoded by the codons UAC and UAU in messenger RNA.
Porphyrins are a group of heterocyclic, macrocyclic, organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges. In vertebrates, an essential member of the porphyrin group is heme, which is a component of hemoproteins, whose functions include carrying oxygen in the bloodstream. In plants, an essential porphyrin derivative is chlorophyll, which is involved in light harvesting and electron transfer in photosynthesis.
Phloroglucinol is an organic compound with the formula C6H3(OH)3. It is a colorless solid. It is used in the synthesis of pharmaceuticals and explosives. Phloroglucinol is one of three isomeric benzenetriols. The other two isomers are hydroxyquinol (1,2,4-benzenetriol) and pyrogallol (1,2,3-benzenetriol). Phloroglucinol, and its benzenetriol isomers, are still defined as "phenols" according to the IUPAC official nomenclature rules of chemical compounds. Many such monophenolics are often termed polyphenols.
Aflatoxin total synthesis concerns the total synthesis of a group of organic compounds called aflatoxins. These compounds occur naturally in several fungi. As with other chemical compound targets in organic chemistry, the organic synthesis of aflatoxins serves various purposes. Traditionally it served to prove the structure of a complex biocompound in addition to evidence obtained from spectroscopy. It also demonstrates new concepts in organic chemistry and opens the way to molecular derivatives not found in nature. And for practical purposes, a synthetic biocompound is a commercial alternative to isolating the compound from natural resources. Aflatoxins in particular add another dimension because it is suspected that they have been mass-produced in the past from biological sources as part of a biological weapons program.
Phenazine is an organic compound with the formula (C6H4)2N2. It is a dibenzo annulated pyrazine, and the parent substance of many dyestuffs, such as the toluylene red, indulines, and safranines (and the closely related eurhodines). Phenazine crystallizes in yellow needles, which are only sparingly soluble in alcohol. Sulfuric acid dissolves it, forming a deep-red solution.
The Dakin oxidation (or Dakin reaction) is an organic redox reaction in which an ortho- or para-hydroxylated phenyl aldehyde (2-hydroxybenzaldehyde or 4-hydroxybenzaldehyde) or ketone reacts with hydrogen peroxide (H2O2) in base to form a benzenediol and a carboxylate. Overall, the carbonyl group is oxidised, whereas the H2O2 is reduced.
A boronic acid is an organic compound related to boric acid in which one of the three hydroxyl groups is replaced by an alkyl or aryl group. As a compound containing a carbon–boron bond, members of this class thus belong to the larger class of organoboranes.
Tropone or 2,4,6-cycloheptatrien-1-one is an organic compound with some importance in organic chemistry as a non-benzenoid aromatic. The compound consists of a ring of seven carbon atoms with three conjugated alkene groups and a ketone group. The related compound tropolone (2-hydroxy-2,4,6-cycloheptatrien-1-one) has an additional alcohol group next to the ketone. Tropones are uncommon in natural products, with the notable exception of the 2-hydroxyl derivatives, which are called tropolones.
2-Ethylhexanoic acid (2-EHA), commonly known as octoic acid, is the organic compound with the formula CH3(CH2)3CH(C2H5)CO2H. It is a carboxylic acid that is widely used to prepare lipophilic metal derivatives that are soluble in nonpolar organic solvents. 2-Ethylhexanoic acid is a colorless viscous oil. It is supplied as a racemic mixture.
Pancratistatin (PST) is a natural compound initially extracted from spider lily, a Hawaiian native plant of the family Amaryllidaceae (AMD).
Indole is an organic compound with the formula C6H4CCNH3. Indole is classified as an aromatic heterocycle. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indoles are derivatives of indole where one or more of the hydrogen atoms have been replaced by substituent groups. Indoles are widely distributed in nature, most notably as amino acid tryptophan and neurotransmitter serotonin.
Thujaplicin is any of three isomeric tropolone-related natural products that have been isolated from the softwoods of the trees of Cupressaceae family. These compounds are known for their antibacterial, antifungal, and antioxidant properties. They were the first natural tropolones to be made synthetically.
Hinokitiol (β-thujaplicin) is a natural monoterpenoid found in the wood of trees in the family Cupressaceae. It is a tropolone derivative and one of the thujaplicins. Hinokitiol is used in oral and skin care products, and is a food additive used in Japan.
The Markó–Lam deoxygenation is an organic chemistry reaction where the hydroxy functional group in an organic compound is replaced by a hydrogen atom to give an alkyl group. The Markó-Lam reaction is a variant of the Bouveault–Blanc reduction and an alternative to the classical Barton–McCombie deoxygenation. It is named for the Belgian chemists István Markó and Kevin Lam.
Spinochrome E is a polyhydroxylated 1,4-naphthoquinone pigment found in sea urchin shell ("test"), spine, gonads, coelomic fluid, and eggs, of sea urchin commonly known as spinochromes. These natural phenolic compounds are quinones with potential pharmacological properties. The several hydroxyl groups are appropriate for free-radical scavenging, which diminishes ROS and prevents redox imbalance. Mechanisms are described such as scavenging of reactive oxygen species (ROS), interaction with lipid peroxide radicals, chelation of metal ions, inhibition of lipid peroxidation and regulation of the cell redox potential.
Syringic acid is a naturally occurring phenolic compound and dimethoxybenzene that is commonly found as a plant metabolite.
Tetsuo Nozoe was a Japanese organic chemist. He is known for the discovery of hinokitiol, a seven-membered aromatic compound, and studying non-benzenoid aromatic compounds.
Thujaplicinol is either of two isomeric tropolone-related natural products. They are found in tree species primarily in bark, needles, xylem, of the family of Cupressaceae like the Cupressus, Thuja, Juniperus and Thujopsis. The thujaplicinols are structurally equivalent to the thujaplicins with an additional hydroxyl group. They belong to the class of natural terpenoids having two free hydroxyl groups at C3 and C5 position.
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