The dextrorotatory form, (+)-nicotine is physiologically less active than (−)-nicotine. (−)-nicotine is more toxic than (+)-nicotine. The salts of (+)-nicotine are usually dextrorotatory; this conversion between levorotatory and dextrorotatory upon protonation is common among alkaloids. The hydrochloride and sulfate salts become optically inactive if heated in a closed vessel above 180 °C.
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Rather, it indicates the compound's stereochemistry relative to that of the dextrorotatory or levorotatory enantiomer of glyceraldehyde. The dextrorotatory isomer of glyceraldehyde is, in fact, the isomer. Nine of the nineteen -amino acids commonly found in proteins are dextrorotatory (at a wavelength of 589 nm), and -fructose is also referred to as levulose because it is levorotatory. A rule of thumb for determining the isomeric form of an amino acid is the "CORN" rule.
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Dexibuprofen is a nonsteroidal anti-inflammatory drug (NSAID). It is the active dextrorotatory enantiomer of ibuprofen. Most ibuprofen formulations contain a racemic mixture of both isomers.
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If the D ring is "below" the core (dextrorotatory), the analgesic and euphoric properties are eliminated or are dramatically reduced, but the cough-suppressant property is retained, as in dextromethorphan.
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Sometimes the D\- and L\- stereodescriptors mentioned above are mistakenly confused with obsolete small capital italic d- and l- stereodescriptors, which are equivalent with dextrorotatory and levorotatory optical rotation, i.e. (+)- and (−)- stereodescriptors, respectively.
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In Latvia, Lithuania and Estonia it is available as an OTC under the tradename Dolmen In Mexico it is available in tablet form as "Stadium" made by Menarini. It is the dextrorotatory stereoisomer of ketoprofen.
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The pharmacokinetics of zopiclone in humans are stereoselective. After oral administration of the racemic mixture, Cmax (time to maximum plasma concentration), area under the plasma time-concentration curve (AUC) and terminal elimination half-life values are higher for the dextrorotatory enantiomers, owing to the slower total clearance and smaller volume of distribution (corrected by the bioavailability), compared with the levorotatory enantiomer. In urine, the concentrations of the dextrorotatory enantiomers of the N-demethyl and N-oxide metabolites are higher than those of the respective antipodes. The pharmacokinetics of zopiclone are altered by aging and are influenced by renal and hepatic functions.
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Dexchlorpheniramine (trade name Polaramine) is an antihistamine with anticholinergic properties used to treat allergic conditions such as hay fever or urticaria. It is the pharmacologically active dextrorotatory isomer of chlorpheniramine. It was patented in 1962 and came into medical use in 1959.
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Snow, p. 1 MDMA was produced in 1912 (according to other sources in 1914) as an intermediate product. However, this synthesis also went largely unnoticed.Goldfrank, p. 1125 In the 1920s, both methamphetamine and the dextrorotatory optical isomer of amphetamine, dextroamphetamine, were synthesized.
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It indicates that the C-5 chiral center has the same handedness as that of -glyceraldehyde (which was so labeled because it is dextrorotatory). The fact that -glucose is dextrorotatory is a combined effect of its four chiral centers, not just of C-5; and indeed some of the other -aldohexoses are levorotatory. The conversion between the two anomers can be observed in a polarimeter, since pure α-glucose has a specific rotation angle of +112.2°·ml/(dm·g), pure β- D- glucose of +17.5°·ml/(dm·g).Manfred Hesse, Herbert Meier, Bernd Zeeh, Stefan Bienz, Laurent Bigler, Thomas Fox: Spektroskopische Methoden in der organischen Chemie.
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Dexbrompheniramine is an antihistamine with anticholinergic properties used to treat allergic conditions such as hay fever or urticaria. It is the pharmacologically active dextrorotatory isomer of brompheniramine. It was formerly marketed in combination with pseudoephedrine under the name Drixoral in the US and Canada. It is an alkylamine antihistamine.
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Dextrorphan (DXO) is a psychoactive drug of the morphinan class which acts as an antitussive or cough suppressant and dissociative hallucinogen. It is the dextrorotatory-stereoisomer of racemorphan, the levo-half being levorphanol. Dextrorphan is produced by O-demethylation of dextromethorphan by CYP2D6. Dextrorphan is an NMDA antagonist and contributes to the psychoactive effects of dextromethorphan.
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Instead, there is axial chirality, which results from the handedness of the helicity itself. The clockwise and counterclockwise helices are non-superposable. By convention a left-handed helix is minus and labeled (M), a right-handed helix is plus and labeled (P). Evidence from CD spectroscopy suggests left-handed helices are levorotatory and right-handed helices are dextrorotatory.
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An enantiomer can be named by the direction in which it rotates the plane of polarized light. Clockwise rotation of the light traveling toward the viewer is labeled (+) enantiomer. Its mirror-image is labeled (−). The (+) and (−) isomers have been also termed d- and l- (for dextrorotatory and levorotatory); But, naming with d- and l- is easy to confuse with - and - labeling and is therefore discouraged by IUPAC.
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The term optical activity is derived from the interaction of chiral materials with polarized light. In a solution, the (−)-form, or levorotatory form, of an optical isomer rotates the plane of a beam of linearly polarized light counterclockwise. The (+)-form, or dextrorotatory form, of an optical isomer does the opposite. The rotation of light is measured using a polarimeter and is expressed as the optical rotation.
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Bicalutamide is a racemic mixture consisting of equal proportions of enantiomers (R)-bicalutamide (dextrorotatory) and (S)-bicalutamide (levorotatory). Its systematic name () is (RS)-N-[4-cyano-3-(trifluoromethyl)phenyl]-3-[(4-fluorophenyl)sulfonyl]-2-hydroxy-2-methylpropanamide. The compound has a chemical formula of C18H14F4N2O4S, a molecular weight of 430.373 g/mol, and is a fine white to off-white powder. The acid dissociation constant (pKa') of bicalutamide is approximately 12.
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"TMP" refers to a threo product that does not contain any erythro diastereomers, i.e. (±)-threo- methylphenidate. Since the threo isomers are energetically favored, it is easy to epimerize out any of the undesired erythro isomers. The drug that contains only dextrorotatory methylphenidate is sometimes called d-TMP, although this name is only rarely used and it is much more commonly referred to as dexmethylphenidate, d-MPH, or d-threo-methylphenidate.
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Levorphanol and its stereoisomer dextrorphan, the enantiomers of the racemic mixture racemorphan. Chemically, levorphanol belongs to the morphinan class and is (−)-3-hydroxy-N-methyl-morphinan. It is the "left-handed" (levorotatory) stereoisomer of racemorphan, that is the racemic mixture of the two stereoisomers with differing pharmacology. The "right-handed" (dextrorotatory) enantiomer of racemorphan is dextrorphan (DXO), an antitussive, potent dissociative hallucinogen (NMDA receptor antagonist), and weakly active opioid.
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The first patented amphetamine brand, Benzedrine, was a racemic (i.e., equal parts) mixture of the free bases or sulfate salts of both amphetamine enantiomers (levoamphetamine and dextroamphetamine) that was introduced in the United States in 1934 as an inhaler for treating nasal congestion. It was later realized that the amphetamine enantiomers could treat obesity, narcolepsy, and ADHD. Because of the greater central nervous system effect of the dextrorotatory enantiomer (i.e.
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Dextromethorphan is the dextrorotatory enantiomer of levomethorphan, which is the methyl ether of levorphanol, both opioid analgesics. It is named according to IUPAC rules as (+)-3-methoxy-17-methyl-9α,13α,14α-morphinan. As its pure form, dextromethorphan occurs as an odorless, opalescent white powder. It is freely soluble in chloroform and insoluble in water; the hydrobromide salt is water-soluble up to 1.5 g/100 mL at 25 °C.
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Pasteur noticed that crystals of tartrates had small faces. Then he observed that, in racemic mixtures of tartrates, half of the crystals were right-handed and half were left-handed. In solution, the right-handed compound was dextrorotatory, and the left-handed one was levorotatory. Pasteur determined that optical activity related to the shape of the crystals, and that an asymmetric internal arrangement of the molecules of the compound was responsible for twisting the light.
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Tocotrienols extracted from plants are always dextrorotatory stereoisomers, signified as d-tocotrienols. In theory, levorotatory forms of tocotrienols (l-tocotrienols) could exist as well, which would have a 2S rather than 2R configuration at the molecules' single chiral center, but unlike synthetic dl-alpha-tocopherol, the marketed tocotrienol dietary supplements are all d-tocotrienol extracts from palm or annatto oils. Preliminary clinical trials on dietary supplement tocotrienols indicate potential for anti-disease activity.
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3-Hydroxymorphinan (3-HM), or morphinan-3-ol, is a psychoactive drug of the morphinan family. It is the racemic counterpart to norlevorphanol. The dextrorotatory stereoisomer of the compound is an active metabolite of dextromethorphan, dextrorphan, and 3-methoxymorphinan, and similarly to them has potent neuroprotective and neurotrophic effects on LTS- and MPTP-treated dopaminergic neurons of the nigrostriatal pathway, but notably without producing any neuropsychotoxic side effects (e.g., dissociation or hallucinations) or having any anticonvulsant actions.
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Flunoxaprofen is pharmacologically activated through biotransformation of the R-enantiomer to the S-enantiomer. This highly stereoselective chiral inversion is mediated by the FLX-S-Acyl-CoA thioester. Pharmacokinetic studies have been carried out by determining the level of propranolol enantiomers in the plasma after administering the racemic drug orally. It has been shown that the dextrorotatory form is particularly active and has a much higher therapeutic index than some other anti-inflammatories, including indomethacin and diclofenac.
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Telbivudine is a synthetic thymidine β-L-nucleoside analogue; it is the L-isomer of thymidine. Telbivudine impairs hepatitis B virus (HBV) DNA replication by leading to chain termination. It differs from the natural nucleotide only with respect to the location of the sugar and base moieties, taking on an levorotatory configuration versus a dextrorotatory configuration as do the natural deoxynucleosides. It is taken orally in a dose of 600 mg once daily with or without food.
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Whether in water or in the solid form, -(+)-glucose is dextrorotatory, meaning it will rotate the direction of polarized light clockwise as seen looking toward the light source. The effect is due to the chirality of the molecules, and indeed the mirror-image isomer, -(−)-glucose, is levorotatory (rotates polarized light counterclockwise) by the same amount. The strength of the effect is different for each of the five tautomers. Note that the - prefix does not refer directly to the optical properties of the compound.
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Therefore, for example, allopumiliotoxin 339A is an allopumiliotoxin with a molecular weight of 339 g/mol but there are other isomers with the same molecular weight. Allopumiliotoxin 339A has an axially oriented hydroxyl group at the 7-position in the indolizidine nucleus that differentiates it from allopumiliotoxin 339B. A (+) or (-) sign preceding the name of an allopumiliotoxin refers to the compound’s optical activity. Compounds that rotate a plane of polarized light clockwise are referred to as dextrorotatory and are preceded by a (+) sign.
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Levofenfluramine (INN), or (−)-3-trifluoromethyl-N-ethylamphetamine, also known as (−)-fenfluramine or (R)-fenfluramine, is a drug of the amphetamine family that, itself (i.e., in enantiopure form), was never marketed. It is the levorotatory enantiomer of fenfluramine, the racemic form of the compound, whereas the dextrorotatory enantiomer is dexfenfluramine. Both fenfluramine and dexfenfluramine are anorectic agents that have been used clinically in the treatment of obesity (and hence, levofenfluramine has been as well since it is a component of fenfluramine).
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In this system, compounds are named by analogy to glyceraldehyde, which, in general, produces unambiguous designations, but is easiest to see in the small biomolecules similar to glyceraldehyde. One example is the chiral amino acid alanine, which has two optical isomers, and they are labeled according to which isomer of glyceraldehyde they come from. On the other hand, glycine, the amino acid derived from glyceraldehyde, has no optical activity, as it is not chiral (achiral). The labeling is unrelated to (+)/(−); it does not indicate which enantiomer is dextrorotatory and which is levorotatory.
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Levonorgestrel, also known as 17α-ethynyl-18-methyl-19-nortestosterone or as 17α-ethynyl-18-methylestr-4-en-17β-ol-3-one, is a synthetic estrane steroid and a derivative of testosterone. It is the C13β or levorotatory stereoisomer and enantiopure form of norgestrel, the C13α or dextrorotatory isomer being inactive. Levonorgestrel is more specifically a derivative of norethisterone (17α-ethynyl-19-nortestosterone) and is the parent compound of the gonane (18-methylestrane) subgroup of the 19-nortestosterone family of progestins. Levonorgestrel acetate and levonorgestrel butanoate are C17β esters of levonorgestrel.
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His research work with Ram Nath Chopra brought out the first scientific paper on Sarpagandha (Rauvolfia serpentina) and its medical properties. His research on the medicinal values of Alstonia scholaris, Caesalpinia bonducella and snake venom are well documented. His research on posterior pituitary hormones and their effects on liver fat helped initiate a research program at School of Medicine, Toronto University the findings of which explained the lipotropic actions of choline, betaine and methionine. He also did research on dextrorotatory hydroocupridine derivatives, anterior pituitary extracts and cyanide poisoning.
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Levomethadone, sold under the brand name L-Polamidon among others, is a synthetic opioid analgesic and antitussive which is marketed in Europe and is used for pain management and in opioid maintenance therapy. In addition to being used as a pharmaceutical drug itself, levomethadone is the main therapeutic component of methadone. Where it is used, levomethadone is used for narcotic maintenance in place of, or in some cases alongside as an alternative, to racemic methadone, owing to concern about the cardiotoxic and QT-prolonging action of racemic methadone being exclusively caused by the dextrorotatory enantiomer, dextromethadone.
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Doisynolic acid is a synthetic, nonsteroidal, orally active estrogen that was never marketed. The reaction of estradiol or estrone with potassium hydroxide, a strong base, results in doisynolic acid as a degradation product, which retains high estrogenic activity, and this reaction was how the drug was discovered, in the late 1930s. The drug is a highly active and potent estrogen by the oral or subcutaneous route. The reaction of equilenin or dihydroequilenin with potassium hydroxide was also found to produce bisdehydrodoisynolic acid, the levorotatory isomer of which is an estrogen with an "astonishingly" high degree of potency, while the dextrorotatory isomer is inactive.
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Like many chiral molecules, the two stereoisomers of glyceraldehyde will gradually rotate the polarization direction of linearly polarized light as it passes through it, even in solution. The two stereoisomers are identified with the prefixes - and -, according to the sense of rotation: -glyceraldehyde is dextrorotatory (rotates the polarization axis clockwise), while -glyceraldehyde is levorotatory (rotates it counterclockwise). \- and -glucose The - and - prefixes are also used with other monosaccharides, to distinguish two particular stereoisomers that are mirror-images of each other. For this purpose, one considers the chiral carbon that is furthest removed from the C=O group.
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C2H2O4, m.p. 221–222 °C, and the tartrate (Sympatol), (C9H13NO2)2.C4H6O6, m.p. 188–190 °C.The Merck Index, 10th Ed. (1983), p. 1295, Merck & Co., Rahway, NJ. The presence of the hydroxy-group on the benzylic C of the synephrine molecule creates a chiral center, so the compound exists in the form of two enantiomers, d- and l- synephrine, or as the racemic mixture, d,l- synephrine. The dextrorotatory d-isomer corresponds to the (S)-configuration, and the levorotatory l-isomer to the (R)-configuration.J. M. Midgley, C. M. Thonoor, A. F. Drake, C. M. Williams, A. E. Koziol and G. J. Palenik (1989).
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The two asymmetric crystal forms, dextrorotatory and levorotatory, of tartaric acid. Sucrose solution concentration measuring experiment, demonstrating optical rotation. The rotation of the orientation of linearly polarized light was first observed in 1811 in quartz by French physicist François Jean Dominique Arago.Arago (1811) "Mémoire sur une modification remarquable qu'éprouvent les rayons lumineux dans leur passage à travers certains corps diaphanes et sur quelques autres nouveaux phénomènes d'optique" (Memoir on a remarkable modification that light rays experience during their passage through certain translucent substances and on some other new optical phenomena), Mémoires de la classe des sciences mathématiques et physiques de l'Institut Impérial de France, 1st part : 93–134.
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Fructose is even more strongly levorotatory than glucose is dextrorotatory. Invert sugar syrup, commercially formed by the hydrolysis of sucrose syrup to a mixture of the component simple sugars, fructose, and glucose, gets its name from the fact that the conversion causes the direction of rotation to "invert" from right to left. In 1849, Louis Pasteur resolved a problem concerning the nature of tartaric acid.Pasteur, L. (1850) "Recherches sur les propriétés spécifiques des deux acides qui composent l'acide racémique" (Researches on the specific properties of the two acids that compose the racemic acid), Annales de chimie et de physique, 3rd series, 28 : 56–99 ; see also appendix, pp. 99–117.
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Tocotrienols have only a single chiral center, which exists at the 2' chromanol ring carbon, at the point where the isoprenoid tail joins the ring. The other two corresponding centers in the phytyl tail of the corresponding tocopherols do not exist as chiral centers for tocotrienols due to unsaturation (C-C double bonds) at these sites. Tocotrienols extracted from plants are always dextrorotatory stereoisomers, signified as d-tocotrienols. In theory, (levorotatory; l-tocotrienol) forms of tocotrienols could exist as well, which would have a 2S rather than 2R configuration at the molecules' single chiral center, but unlike synthetic, dl-alpha-tocopherol, the marketed tocotrienol dietary supplements are all d-tocotrienol extracts from palm or annatto oils.
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They are also abundant components of the peptidoglycan cell walls of bacteria, and D-serine may act as a neurotransmitter in the brain. D-amino acids are used in racemic crystallography to create centrosymmetric crystals, which (depending on the protein) may allow for easier and more robust protein structure determination. The L and D convention for amino acid configuration refers not to the optical activity of the amino acid itself but rather to the optical activity of the isomer of glyceraldehyde from which that amino acid can, in theory, be synthesized (D-glyceraldehyde is dextrorotatory; L-glyceraldehyde is levorotatory). In alternative fashion, the (S) and (R) designators are used to indicate the absolute configuration.
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Dextroamphetamine is the dextrorotatory, or 'right-handed', enantiomer and exhibits more pronounced effects on the central nervous system than levoamphetamine. Pharmaceutical dextroamphetamine sulfate is available as both a brand name and generic drug in a variety of dosage forms. Dextroamphetamine is sometimes prescribed as the inactive prodrug lisdexamfetamine dimesylate, which is converted into dextroamphetamine after absorption. Dextroamphetamine, like other amphetamines, elicits its stimulating effects via several distinct actions: it inhibits or reverses the transporter proteins for the monoamine neurotransmitters (namely the serotonin, norepinephrine and dopamine transporters) either via trace amine-associated receptor 1 (TAAR1) or in a TAAR1 independent fashion when there are high cytosolic concentrations of the monoamine neurotransmitters and it releases these neurotransmitters from synaptic vesicles via vesicular monoamine transporter 2.
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The presence of multiple chiral features in a given compound increases the number of geometric forms possible, though there may still be some perfect-mirror-image pairs. A sample of a chemical is considered enantiopure (also termed enantiomerically pure) when it has, within the limits of detection, molecules of only one chirality. When present in a symmetric environment, enantiomers have identical chemical and physical properties except for their ability to rotate plane-polarized light (+/−) by equal amounts but in opposite directions (although the polarized light can be considered an asymmetric medium). Such compounds are therefore described as optically active, with specific terms for each enantiomer based on the direction: a dextrorotatory compound rotates light a clockwise (+) direction whereas a levorotatory compound rotates light in a counter-clockwise (–) direction.
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F-actin; surface representation of a repetition of 13 subunits based on Ken Holmes' actin filament model The classical description of F-actin states that it has a filamentous structure that can be considered to be a single stranded levorotatory helix with a rotation of 166° around the helical axis and an axial translation of 27.5 Å, or a single stranded dextrorotatory helix with a cross over spacing of 350–380 Å, with each actin surrounded by four more. The symmetry of the actin polymer at 2.17 subunits per turn of a helix is incompatible with the formation of crystals, which is only possible with a symmetry of exactly 2, 3, 4 or 6 subunits per turn. Therefore, models have to be constructed that explain these anomalies using data from electron microscopy, cryo-electron microscopy, crystallization of dimers in different positions and diffraction of X-rays. It should be pointed out that it is not correct to talk of a “structure” for a molecule as dynamic as the actin filament.
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