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Topic: Enantiomer

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	Enantiomer - Wikipedia, the free encyclopedia
		Enantiomers have - when present in a symmetric environment - identical chemical and physical properties except for their ability to rotate plane-polarized light by equal amounts but in opposite directions.
		A solution of equal parts of an optically-active isomer and its enantiomer is known as a racemic solution and has a net rotation of plane-polarized light of zero.
		Thalidomide is an example of a racemic drug, in which one enantiomer produces a desirable antiemetic effect, whereas the other is toxic and produces a teratogenic side-effect.
	en.wikipedia.org /wiki/Enantiomer (499 words)

	[No title] (Site not responding. Last check: 2007-10-13)
		The magnitude of the constant for the first enantiomer and the second enantiomer is the same, although the presence of the solvent (for example if a chiral solvent is used) may cause a discrepancy in the measurement which may be easily compensated for.
		The proportions of the two enantiomers in the remaining mixture before entering the column are not equally distributed but the leading edge is now richer in the first enantiomer than the original mixture, and the trailing edge is richer in the second enantiomer.
		In general, the efficiency with which the enantiomer mixture is separated increases with the number of passes through the column, since amounts of enantiomer mixture decrease and the chiral stationary phase becomes either less saturated or unsaturated and the relative proportions of the enantiomers in any particular portion of mobile phase become less equal.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=04/00761.031231&ELEMENT_SET=DECL (2655 words)

	Racemic - Wikipedia, the free encyclopedia
		It's the mechanical mixture of enantiomerically pure crystals of one enantiomer and its opposite.
		The melting point of the racemic conglomerate is always lower than the pure enantiomer.
		The reagents of, and the reactions that produce, racemic mixtures are said to be "not stereospecific" or "not stereoselective", for their indecision in a particular stereoisomerism.
	en.wikipedia.org /wiki/Racemic (290 words)

	BIP - Lipase-catalyzed enantioselective esterification of flurbiprofen with n-butanol
		Enzymes discriminate between the enantiomers of a compound, and the rate of the enzyme-catalyzed reaction of one enantiomer with a reagent may differ vastly from that of its antipode.
		One approach that may be used to obtain a pure enantiomer of flurbiprofen from its racemic mixture is to use lipase in an organic medium to catalyze the esterification of the flurbiprofen with an alcohol, such as n-butanol.
		The results of this study suggest that the enantioselective esterification of flurbiprofen catalyzed by lipases is significantly influenced by the nature of the solvent, the source of the lipase, and the activity of water in the reaction medium.
	www.ejbiotechnology.info /content/vol3/issue3/full/3/bip (1145 words)

	Optical Activity
		In a pair of optically active enantiomers, each enantiomer will rotate the plane of polarized light in equal and opposite directions; the enantiomers can therefore be referred to as (+) and (-) enantiomers, depending upon the direction of the observed rotation.
		The angle of rotation is measured in a device known as a polarimeter.
		The specific rotation for a pure enantiomer is known to be -39
	www.chem.uic.edu /web1/OCOL-II/WIN/STEREO/31/OA.HTM (406 words)

	Andrew M. Goldsweig's Enantiomer Page (Site not responding. Last check: 2007-10-13)
		To determine whether two molecules are enantiomers, diastereomers, or the same compound, one must study the bonding structure of the molecules in question.
		One enantiomer is said to be dextrorotatory (denoted with a d or a +) because it rotates light to the right or clockwise.
		Thus, a racemic mixture, which is composed of equal amounts of each enantiomer of a compound, should exhibit no optical activity since the effects of the different isomers negate each other.
	www-personal.umich.edu /~dgoldswe/mit/dcds/enantiomers.html (449 words)

	United States Patent Application: 0030199709
		The (-) enantiomer of a compound of formula (IV) or salts thereof: 23wherein R is H or alkyl and Y, Y.sup.1 and Z are Cl or Br.
		The (+) enantiomer of a compound of formula (IV) or salts thereof: 24wherein R is H or alkyl and Y, Y.sup.1 and Z are Cl or Br.
		Thus compounds of formula VII or their enantiomers may be converted to compounds of formula VI or their enantiomers by reaction with a chlorinating agent and then esterified to a compound of formula (V) as described in `March 4.sup.th Edition--p437-38 and p392` respectively.
	appft1.uspto.gov /netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/PTO/search-bool.html&r=1&f=G&l=50&co1=AND&d=PG01&s1=20030199709&OS=20030199709&RS=20030199709 (7265 words)

	The Nobel Prize in Chemistry 2001 - Information for the Public
		Since the two enantiomers of a chiral molecule often have totally different effects on cells, it is important to be able to produce each of the two forms pure.
		In the chiral hydrogenation one of the enantiomers of DiPAMP was used.
		The two enantiomers of Noyori's useful BINAP is shown together with an example of a stereoselective ketone reduction where the ester function is left intact.
	nobelprize.org /chemistry/laureates/2001/public.html (2498 words)

	Science News Online (4/4/98): Ritalin may work better as purer compound by C. Wu
		According to the Brookhaven analysis, one enantiomer is much more potent than the other and is responsible for Ritalin's beneficial effects of improving attention and reducing impulsivity.
		Previous studies have indicated that the two enantiomers of methylphenidate cause different behavioral responses in patients, but the Brookhaven study visually establishes where the drug acts in the human brain, says William F. Trager of the University of Washington in Seattle.
		Administering Ritalin as a single enantiomer may not be necessary, says Trager, since the body seems to metabolize the mirror-image molecules differently, thereby enriching the blood with the more potent form.
	www.sciencenews.org /sn_arc98/4_4_98/fob3.htm (545 words)

	040701origin.html
		In this proposed biased synthesis of enantiomers the bias would be the same anywhere in the universe for the same synthesis under the same conditions.
		If both enantiomers were present in the droplet, and if their electric axis and paramagnetic axis were not coincident, one enantiomer would have its 'front' facing the radiation and the shock wave from the stroke; the other enantiomer would have its 'back' facing the radiation and the shock wave.
		The effects of the energy received by the two enantiomers from these sources might be different because of the different orientation of the molecules with respect to the stroke.
	www.geocities.com /acgyles/origin.html (3990 words)

	Amphetamine Enantiomer Excretion Profile Following Administration of Adderall* (Site not responding. Last check: 2007-10-13)
		To address this situation, a study to determine the concentration and enantiomer composition of amphetamine excretion following administration of Adderall was undertaken.
		Because of the mixture of enantiomers, not all samples that contained > 500 ng/mL of amphetamine were positive when tested by immunoassay.
		Because the enantiomers are metabolized at different rates, their proportion offers the opportunity to describe excretion versus time.
	www.jatox.com /abstracts/2003/october/485-cody.html (524 words)

	[No title] (Site not responding. Last check: 2007-10-13)
		The pure enantiomers of the compound of formula I can be obtained starting from the racemate by procedures known as such.
		The racemate may be separated into its enantiomers through the formation of diastereomeric salts, for example by salt formation with an enantiomer-pure chiral acid, or by means of chromatography, for example by HPLC, using chromatographic substrates with chiral ligands.
		They clearly demonstrate that the R- enantiomer at the highest dose used (200 mg/kg) is less efficacious than the S-enantiomer at the lowest dose used (50 mg/kg), whereas the potency/efficacy ratio of the Racemate is between that of the R-and S-enantiomers.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=04/71152.040826&ELEMENT_SET=DECL (2747 words)

	Stereochemical Glossary
		enantiomer (R) -- (1) A stereoisomer of a reference compound or structure that is the nonsuperimposable mirror image of the reference compound or structure.
		Enantiomers have identical internal dimensions (interatomic distances, dihedral angles) and identical energies, but they rotate plane-polarized light in equal but opposite directions, and they interact with other chiral objects in different ways.
		The ee of a sample of a compound can be measured by dividing the specific rotation of the sample by the specific rotation of an enantiomerically pure sample of the same compound.
	www.chem.uky.edu /research/grossman/stereo/stereogloss.html (3190 words)

	Re: Who coined the word enantiomer?
		An "enantiomer" is one of a pair of substances whose molecules are mirror images of one another.
		"enantiomer" does not appear in the Oxford English Dictionary, or at least not in the versions and editions that I have ready access to.
		I suggest that "enantiomer" is a fairly obvious and natural contraction of "enantiomorpic isomer" that may have crept fairly naturally into the technical language between 1880 and 1930.
	www.madsci.org /posts/archives/1999-10/941203265.Sh.r.html (477 words)

	Enantiomer selectivity and the development of tolerance to the behavioral effects of the calcium channel activator BAY ... (Site not responding. Last check: 2007-10-13)
		Enantiomer selectivity and the development of tolerance to the behavioral effects of the calcium channel activator BAY K 8644.
		Enantiomer selectivity and the development of tolerance to the behavioral effects of the calcium channel activator BAY K 8644.(+/-)- BAY K 8644 produced convulsions in mice with a CD50 of 5 mg/kg.
		The interaction of the enantiomers of BAY K 8644 with mouse brain dihydropyridine binding sites was also evaluated.
	www.pdg.cnb.uam.es /UniPub/iHOP/gp/5801845.html (284 words)

	Stereospecific Analysis and Enantiomeric Disposition of 3,4-Methylenedioxymethamphetamine (Ecstasy) in Humans -- Fallon ... (Site not responding. Last check: 2007-10-13)
		Single enantiomer MDMA and MDA authentic standards in plasma are at concentrations of 0.5 and 0.05 µg/L, respectively.
		Pharmacokinetic parameters of the individual enantiomers of MDMA after the administration of the racemic drug (40 mg) to healthy male volunteers.
		The simultaneous separation and quantitation of the enantiomers of MDMA and MDA using gas chromatography with nitrogen-phosphorous detection.
	www.clinchem.org /cgi/content/full/45/7/1058 (5834 words)

	Enantioselectivity in environmental safety of current chiral insecticides -- Liu et al. 102 (3): 701 -- Proceedings of ...
		as the ratio of (+) enantiomers to (-) enantiomers, increasingly
		enantiomers to be recovered for use in bioassays.
		(+) enantiomer and that peak II was derived from the (-) enantiomer.
	www.pnas.org /cgi/content/full/102/3/701 (2881 words)

	IMS Health - Pharmaceutical market intelligence (Site not responding. Last check: 2007-10-13)
		These two stereoisomers or enantiomers are structurally identical, with the same physical properties, differing only in their three-dimensional spatial arrangement.
		Although the majority of their therapeutic effect is due to the (S)-enantiomer, the difference in activity between the two enantiomers means that the (R)-enantiomer has little effect on the drug’s activity and does not cause any serious side-effects.
		While there are examples where both enantiomers have similar therapeutic properties, for instance ibuprofen, there are cases where one of the isomers causes serious side-effects.
	open.imshealth.com /webshop2/IMSinclude/i_article_20030123.asp (1177 words)

	Racemization
		If you have two enantiomers in a mixture that have the same number of molecules, then half of the molecules will rotate plane polarized light in one direction and the other half of the molecules will rotate the light in the opposite the same number of degrees.
		There are some reactions where one enantiomer is produced in excess of the other primarily because one side of the reactant molecule or intermediate was hindered so that side of access was less likely than the less hindered side.
		Let's suppose that we have a reaction mixture which we measure for rotation, and the observed specific rotation of the reaction mixture is measured to be +8.52 degrees of rotation.
	members.aol.com /logan20/racemate.html (1483 words)

	Influence of Environmental Changes on Degradation of Chiral Pollutants in Soils, Exposure Research, US EPA
		Organic nutrient enrichment in the laboratory shifted enantioselectivity for methyl dichlorprop strongly toward preferentially removing the non-herbicidal enantiomer in soils from Brazil (from 2% to 50% preference) and the USA (from 48% to 80%).
		These results show that environmental changes can cause the beneficial enantiomer B the one active to the target species B of a chiral compound to be more persistent or less persistent in the environment than before the change.
		The ultimate goal is to couple information on the environmental enantioselectivity, and thus the persistence, of the respective enantiomers of important chiral pollutants with information on the effects of each enantiomer for use in improving risk assessments.
	www.epa.gov /nerl/research/1999/html/g8-4.html (961 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		The enantiomer ratio (ER) is currently the standard descriptor of enantiomeric (chiral) signatures for environmental samples.
		In this paper, the authors argue for the adoption of the enantiomer fraction (EF) as the standard descriptor by showing drawbacks to the use of ER.
		The enantiomer fraction is superior because it provides a more meaningful representation of graphical data and is more easily employed in mathematical fate expressions.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=20014631 (201 words)

	Stereoselective Metabolism of Cisapride and Enantiomer-Enantiomer Interaction in Human Cytochrome P450 Enzymes: Major ...
		for the inhibition of metabolism of cisapride enantiomers by troleandomycin,
		(enantiomers and racemic) was 11.6 ± 1.1 min.
		The ability of one enantiomer of cisapride to inhibit the metabolism of the other was tested after incubation of both enantiomers
	jpet.aspetjournals.org /cgi/content/full/298/2/508 (7484 words)

	Preferential Pulmonary Retention of (S)-Albuterol after Inhalation of Racemic Albuterol -- DHAND et al. 160 (4): 1136 ...
		clearance of the enantiomers of terbutaline by the kidney (28).
		Determination of salbutamol enantiomers in human plasma and urine by chiral high-performance liquid chromatography.
		Analysis of salbutamol enantiomers in human urine by chiral high-performance liquid chromatography and preliminary studies related to the stereoselective disposition kinetics in man. J.
	ajrccm.atsjournals.org /cgi/content/full/160/4/1136 (4173 words)

	Special report
		Single enantiomers remain important among the top 300, Ba says, with 158 drugs, which accounted for $64.7 billion out of a total of $124.4 billion.
		The situation is the same for the top 500 drugs, where single enantiomers number 269, with 1997 sales of $71.1 billion, or 52% of $135.9 billion total.
		Sometimes, the pharmaceutical activity is in only one enantiomer and the other is inactive, or the "other" enantiomer has a different kind of activity from the first.
	pubs.acs.org /hotartcl/cenear/980921/drugs.html (4986 words)

	Enantiomer - (Site not responding. Last check: 2007-10-13)
		Enantiomers have - when present in a symmetric environment - identical chemical and physical properties except for their ability to rotate plane polarized light by equal amounts but in opposite directions.
		The Food and Drug Administration (FDA) of the United States of America recently recommended that drug molecules having stereocentres should be given to patients only in the active enantiomeric form and not as a racemic mixture.
		Course notes for a lecturer's introduction to stereochemistry and enantiomers.
	www.grohol.com /psypsych/Enantiomer (446 words)

	Test for the Correct Enantiomer (Site not responding. Last check: 2007-10-13)
		The test for the correct enantiomer can be carried out either at the substructure level or after the coordinates of all atoms have been generated.
		This enantiomer testing method is included in the file ``dg_sub_embed.inp" as a comment; to activate it, the user has to uncomment the appropriate lines.
		Again, this enantiomer testing method is included in the file ``dg_sub_embed.inp" as a comment; to activate it, the user has to uncomment the appropriate lines.
	www.ocms.ox.ac.uk /mirrored/xplor/manual/htmlman/node393.html (307 words)

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