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Topic: Regioselectivity

In the News (Mon 21 Dec 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	Gephyrotoxin Formal Synthesis: Model Studies
		In an extension of this study, we explored the viability of a secondary azide and the issue of the stereoselectivity of the iminium ion reduction which arises (Scheme 3).
		The regioselectivity of the crucial bond formation favored aryl migration (desired) over alkyl or hydrogen migration (undesired), although the ratio of aryl:alkyl migration was not high (2.3:1 to 1.1:1).
		Initial Efforts to Synthesize Gephyrotoxin, wherein we struggle with the regioselectivity of the indene alkylation and the choice of a synthetic equivalent for the 2-hydroxyethyl side chain.
	www.ch.ic.ac.uk /ectoc/echet98/pub/013/model.htm (739 words)

	RuO4-Mediated oxidation of N-benzylated tertiary amines. 2. Regioselectivity for N,N-dimethyl- and ... (Site not responding. Last check: 2007-10-09)
		The statistically corrected alkyl/benzyl regioselectivity of the oxidation reaction was 4.1 for 1A and 2.1 for 1B.
		Deprotonation of the endocyclic iminium cation to the respective cyclic enamine was observed too in the absence of cyanide.
		The statistically corrected regioselectivity (endocyclic/exocyclic) experienced by the mentioned substrates varied from 0.8 (morpholine derivative) to 2.1 (piperidine compound).
	www.arkat-usa.org /ark/journal/2005/I10_Balaban/1275/AB-1275B.asp (5143 words)

	A divergent approach toward synthesis of myo-inositol p (Site not responding. Last check: 2007-10-09)
		A divergent approach toward synthesis of myo-inositol phosphates: acyl migrations and regioselectivity.
		The acyl migration rate increases with increasing solvent polarity indicating that the intermediate or transition state involved is more polar than the starting material.
		The origin or the regioselectivity was found to be the enhanced nucleophilicity of the 3-alkoxide due to its interaction with the cis-vicinal oxygen of the isopropylidene group possibly via "through-apace a effect".
	www.nyu.edu /classes/ytchang/reprint/p08.html (178 words)

	[No title] (Site not responding. Last check: 2007-10-09)
		The regioselectivity of the enzyme lead to the initiation of the polymerization at only the primary hydroxyl position of ethylglucoside.
		The enantio- and regioselectivity of enzymes is envisioned as a powerful tool that can be used to circumvent tedious protection-deprotection steps.
		As an alternative approach to modify pendant groups on polysaccharide main chains, an enzymatic route was used to regioselectively form fatty acid esters on the backbone of amylose and cellulose.
	chem.poly.edu /gross/research.cfm (5259 words)

	Versatile Route to Polyol Polyesters by Lipase Catalysis (Site not responding. Last check: 2007-10-09)
		Analysis of this spectrum revealed that sorbitol was esterified with high regioselectivity (85 ± 5%) at the primary 1- and 6-positions.
		This difference in regioselectivity may be due to (i) Uyama et al.
		Thus, the regioselectivity of esterification at the 1- and 6-carbons of sorbitol was ~95 ± 2%.
	pubs.acs.org /cgi-bin/jcen?mamobx/36/i22/html/ma0351827.html (2127 words)

	167 (Site not responding. Last check: 2007-10-09)
		The peri-([2+2] or [4+2]), site-(3,4- or 5,6-addition) and regioselective photoadducts in the triplet photoreactions of 2-pyrones with electron-deficient or electron-rich alkenes were considered to be formed through the regioselective 3-β or 6-β two-center interactions at the first-steps, and periselective ring-closures from the biradical intermediates.
		The regioselectivity difference between the photocycloadditions of two cyclic enones, such as 2-cyclohexenone and 2-cyclopentenone were similarly analysed by the FMO method.
		The regioselectivity of the enones was concluded to be controlled mainly by the FMO interactions at the first-steps and by the relative reactivity of the following ring closure of the biradical intermediates from cyclopentenone.
	www.csj.jp /journals/nikka/abs/nikka0003/nk00167a.html (252 words)

	Huisgen 1,3-Dipolar Cycloaddition
		The regioselectivity of the reaction depends on electronic and steric effects and is somewhat predictable.
		The reaction has been modified to a more regioselective, copper-catalyzed stepwise process by the Sharpless group, which is no longer a classic Huisgen Cycloaddition (the nonconcerted mechanism is discussed here: J.
		Many reactions can be performed with high regioselectivity and even enantioselective transformations of prochiral substrates have been published.
	www.organic-chemistry.org /namedreactions/huisgen-1,3-dipolar-cycloaddition.shtm (405 words)

	SDSU Chemistry & Biochemistry: Thomas E. Cole
		We have found that alkenyl groups can be transferred with retention of stereochemistry to a variety of organohaloboranes.
		This reaction appears to be a general route to vinyl boranes with equals or surpasses regioselectivity of hydroboration methods.
		This transmetallation reaction gives a new route to these primary alkyboranes with very high regioselectivity that would be difficult to prepare using previously established routes.
	www.chemistry.sdsu.edu /faculty/Cole (436 words)

	Factors Controlling Regioselectivity in the Reduction of Polynitroaromatics in Aqueous Solution (Site not responding. Last check: 2007-10-09)
		Regioselectivities in the bisulfide reduction of ten polynitroaromatics to monoamine products have been determined; four of these compounds have also been reduced by anoxic sediments in heterogeneous aqueous solution, and the same regioselectivities are observed.
		In particular, at their minimum-energy geometries in aqueous solution, it is the more negative nitro group that is selectively reduced.
		This is consistent with a mechanism where regioselection occurs upon kinetic protonation at the site of maximum negative charge in the radical anion formed after the first electron transfer to the neutral PNA.
	pollux.chem.umn.edu /publications/abstract65.html (263 words)

	Rational engineering of the regioselectivity of TecA tetrachlorobenzene dioxygenase for the transformation of ... (Site not responding. Last check: 2007-10-09)
		Rational engineering of the regioselectivity of TecA tetrachlorobenzene dioxygenase for the transformation of chlorinated toluenes -- Pollmann et al.
		Thus, the regioselectivity of attack as determined by
		Regioselectivity and enantioselectivity of naphthalene dioxygenase during arene cis-dihydroxylation: control by phenylalanine 352 in the alpha subunit.
	mic.sgmjournals.org /cgi/content/full/149/4/903 (4846 words)

	The Use Haloperoxidases in Organic Synthesis: (Site not responding. Last check: 2007-10-09)
		However, haloperoxidases lack substrate specificity and regioselectivity, and the connection of haloperoxidases with the in vivo formation of oxygenated as well as halometabolites has been demonstrated.
		Recently, molecular genetic investigations showed that, at least in bacteria, fungi, and other organisms a different class of halogenases is involved in halo- and oxygenated metabolite formation.
		-dependent halogenases and haloperoxidases show substrate specificity and regioselectivity, and their genes have been detected in many halometabolite-producing organisms, suggesting that this type of halogenating enzymes constitutes the major source for halo- and oxygenated metabolite formation in bacteria and also in other organisms.
	eurasianchemtech.vub.ac.be /contents/02_4_4_221.html (398 words)

	Online Pharmacy, Tramadol, Paxil, antibiotics, amoxicillin, zithromax, Rx Online, pharmaceuticals, DHEA, prescription ...
		Regioselectivity and enantioselectivity of metoprolol oxidation by two variants of cDNA-expressed P4502D6.
		METHODS: The regioselective and enantioselective features of the oxidations of deuterium-labeled pseudoracemic metoprolol were characterized by GC/MS analysis of the substrate and products.
		CONCLUSIONS: The regioselectivity, enantioselectivity, and Km values for the h2D6-Val microsomes resemble those observed for the native P4502D6 in human liver microsomes, whereas the h2D6v2 microsomes deviated remarkably in regioselectivity.
	www.hairmillion.com /rx-online-info/metoprolol-online-rx/metoprolol-online-rx.98.html (677 words)

	Houk Publication List
		Dunn and K. Houk: "The Regioselectivity of [6+4] Cycloadditions of Dienamines to Fulvenes," Tetrahedron Lett., 3411 (1978).
		Yunfeng Hu and K. Houk: "Quantitative Predictions of Substituent and Solvent Effects on the Regioselectivities of Nitrile Oxide Cycloadditions to Electron-Deficient Alkynes," Tetrahedron, 56, 8239-8243 (2000).
		Andrew G. Leach and K. Houk: "The Mechanism and Regioselectivity of the Ene Reactions of Nitroso Compounds: A Theoretical Study of Reactivity, Regioselectivity, and Kinetic Isotope Effects Establishes a Stepwise Path Involving Polarized Diradical Intermediates," Org.
	www.chem.ucla.edu /dept/Faculty/houk/publications.html (14641 words)

	[No title]
		In cases where it is possible, the Diels-Alder reaction involves high regioselectivity and high endo stereoselectivity.
		The Diels-Alder reaction is stereospecific because both carbon-carbon bonds are made simultaneously.
		Predicting the regioselectivity of the reaction (which end of the diene reacts with which end of the dienophile) is a nice application of resonance contributors and electron delocalization.
	www.stolaf.edu /people/hansonr/chem247/ch8summary.txt (720 words)

	Table 1 (Site not responding. Last check: 2007-10-09)
		together with the flexibility of the substrate determines, to what extent chemically similar positions are available for bond activation, and hence, controls the degree of chemo- and regioselectivity.
		For example, a bare metal ion which is capable to initiate remote functionalization in the gas phase is in many cases too reactive to exhibit a high degree of regioselectivity.
		Similar to a recent combined force-field/ab initio approach, the transition structures associated with dehydrogenation of nonane nitrile/Fe were computed and qualitative predictions for the regioselectivity were made.
	www.chem.tu-berlin.de /Detlef.Schroeder/puapch/PUAPCH1.htm (2572 words)

	Computational Models for Cytochrome P450: A Predictive Electronic Model for Aromatic Oxidation and Hydrogen Atom ...
		Szklarz GD and Halpert JR (1997) Use of homology modeling in conjunction with site-directed mutagenesis for analysis of structure-function relationships of mammalian cytochromes P450.
		White RE, McCarthy M, Egeberg KD and Sligar SG (1984) Regioselectivity in the cytochromes P450: control by protein constraints and chemical reactivities.
		White RE, Miller JP, Favreau LV and Bhattachararyya A (1986) Stereochemical dynamics of aliphatic hydroxylation by cytochrome P-450.
	dmd.aspetjournals.org /cgi/content/full/30/1/7 (3830 words)

	CHI's Molecular Med Monthly Articles (Site not responding. Last check: 2007-10-09)
		What distinguishes our approach is that we are able to not just list potential reactive metabolites but also weight them according to their likelihood of being formed.
		For our regioselectivity models, we do quantum-chemical calculations on the molecule, which provide a lot of information about the reactivity and electronic structure of the molecules.
		The throughput of our regioselectivity models right now is on the order of 50,000 compounds per day in a high-throughput mode, and about 5,000 per day in the high-resolution mode.
	www.healthtech.com /newsarticles/issue19_2.asp (1291 words)

	The use of indium in organic chemistry
		Issues such as chemoselectivity, regioselectivity and diastereoselectivity have been extensively investigated.
		The most intriguing result from these studies is the use of free hydroxyl groups to direct the allyl additions to carbonyl compounds (Scheme 4).
		Although much less is known about propargyl indium additions to carbonyl compounds, some preliminary results showed very good regioselectivity on such additions (Scheme 6).
	www.chem.umn.edu /studsem/abstract9900/Pep01.28.00/abstract.html (507 words)

	Synthesis of a protected 2-ethoxy-3-hydroxyethylfuran ;and its regioselectivity as a Diels–Alder diene on reaction ... (Site not responding. Last check: 2007-10-09)
		As a potential route for the synthesis of naturally occurring benzisochromanequinones, 2-ethoxy-3-(1'-methoxymethoxyethyl)furan 15 was prepared and shown to react regioselectively with in situ generated 3,5-dimethoxydehydrobenzene to afford, after hydrolysis and alkylation, the target naphthalene 1-(6',8'-dimethoxy-1'-ethoxy-4'-isopropoxy-2'-naphthalenyl)-1-(methoxymethoxy)ethane 27.
		C-1 and O-2 of the ring system contained in structure 1 as well as the alkyl (usually methyl) substituent connected to C-1 are often derived from a hydroxyalkyl (usually hydroxyethyl) group attached to an appropriate naphthalenic precursor.
		The addition of a small quantity of hydroquinone, to inhibit polymerisation, was found to increase the yield. This product 11 was obtained through the regioselective formation of the Diels-Alder adduct 10, and a subsequent retro–Diels–Alder reaction with the loss of acetonitrile, in a yield of 46% from the starting N-formylalaninate 7.
	www.arkat-usa.org /ark/journal/2002/I03_Lloyd/DL-267G/267.asp (2955 words)

	Using Flash Cards to Learn Reactions
		The making of the cards, in fact, is part of how you use them to study.
		Read over your notes, read the appropriate sections of the text, and "design" a reaction that includes all of the important features: the regioselectivity, the stereoselectivity, and so on.
		For example, if the product shown is a specific stereoisomer of an alcohol, that signals hydroboration, which is our only stereospecific preparation of alcohols (and will remain so all year).
	chemistry.umeche.maine.edu /CHY251/flash.html (659 words)

	Evolution of substrate recognition across a multigene family of glycosyltransferases in Arabidopsis -- Lim et al. 13 ... (Site not responding. Last check: 2007-10-09)
		The possible regioselectivity switching events are indicated by arrows.
		Results from group E are shown in Figure 3A.
		Data from groups H and L are shown in Figures 4 and 5.
	glycob.oxfordjournals.org /cgi/content/full/13/3/139 (3443 words)

	Beilstein Journal of Organic Chemistry \| Abstract \| Mixtures of monodentate P-ligands as a means to control the ...
		The previously reported concept of using mixtures of monodentate ligands in a combinatorial manner in order to influence enantio- or regioselectivity of transition metal catalyzed processes has been extended to include diastereoselectivity.
		It was found that appropriate 1:1 mixtures of two different P-ligands enhance the degree of diastereoselectivity relative to the use of the respective pure ligands themselves.
		Here, as in the previous cases regarding enantio- or regioselectivity, this type of combinatorial catalysis leads to improved catalytic profiles without the need to prepare new ligands.
	bjoc.beilstein-journals.org /content/1/1/3/abstract (197 words)

	Francis Musyoki (Site not responding. Last check: 2007-10-09)
		The Substituent Effects of Electron Donating and Electron Withdrawing Groups on the Regioselectivity of the Ring Contracting Rearrangement of Epoxidized Benzyne/Furan Cycloadducts.
		Since there were no sub stituents on the benzyne used in the Diels-Alder reaction, the benzene ring of the epoxynaphthalene adduct had no substituents and thus, it was not possible to learn the effects of chemical substituents on the regioselectivity of the ring contracting rearrangement reaction.
		It is expected that the substituents on the benzene ring will affect the regioselectivity of the ring contracting rearrangement reaction, favoring the production of one of the two possible 1, 3-dicarbonyl compound products shown in the figure above.
	it.stlawu.edu /~chem/projects98-99/musyoki.htm (413 words)

	Online Pharmacy, Tramadol, Paxil, antibiotics, amoxicillin, zithromax, Rx Online, pharmaceuticals, DHEA, prescription ...
		Altered binding was also manifested in significant differences in regiospecificity with respect to dextromethorphan, producing enzymes with no preference for N-demethylation versus O-demethylation (E216K and E216F).
		Neutralization of Asp-301 to Gln and Asn had similarly profound effects on substrate binding and regioselectivity.
		Intriguingly, removal of the negative charge from either 216 or 301 produced enzymes (E216A, E216K, and D301Q) with elevated levels (50-75-fold) of catalytic activity toward diclofenac, a carboxylate-containing CYP2C9 substrate that lacks a basic nitrogen atom.
	www.hairmillion.com /rx-online-info/diclofenac-online-rx/diclofenac-online-rx.300.html (783 words)

	Chapter 6
		The reactions of alkenes can seem a little bewildering as a wide variety of reagents undergo this type of reaction providing access to products with various regioselectivities and stereoselectivities depending on the reagent and / or reaction conditions, but ultimately on the mechanism by which the reaction occurs.
		There are potentially 3 factors associated with each of the addition reactions of alkenes:
		regioselectivity (provided the two atoms that add are different)
	library.tedankara.k12.tr /carey/ch6-0.html (122 words)

	[No title] (Site not responding. Last check: 2007-10-09)
		Also known as dehydration since it involves the removal of a molecule of water.
		Regioselectivity : major product is usually the more highly substituted alkene (alkene stability) Zaitsev's Rule.
		Regioselectivity is usually controlled by the relative stability of the product alkenes (Zaitsev's rule).
	www.mhhe.com /physsci/chemistry/carey/student/olc/graphics/carey04oc/ref/ch05preparealkenes.html (185 words)

	ARS \| Publication request: Regioselectivity of New Bacterial Lipases Determined by Hydrolysis of Triolein
		Publication request: Regioselectivity of New Bacterial Lipases Determined by Hydrolysis of Triolein
		Citation: Lanser, A.C., Manthey, L.K., Hou, C.T. Regioselectivity Of New Bacterial Lipases Determined By Hydrolysis Of Triolein.
		Of the bacterial lipases tested, fifty-five displayed random specificity, nine were 1,3 specific, and three showed no apparent lipase activity under these conditions.
	ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=118714 (275 words)

	Boger Publications (Site not responding. Last check: 2007-10-09)
		Boger, J. Goldberg, and J. McKie, A comparative study of the solvolysis reactivity, regioselectivity, and stereochemistry of the duocarmycin A and SA alkylation subunits, Bioorg.
		Boger, M. Patel, and F. Takusagawa, Regioselectivity of the intermolecular Diels-Alder reaction of acyl nitroso compounds (C-nitrosocarbonyl compounds) and nitrosoformates (O-nitrosocarbonyl compounds).
		Boger and M. Patel, Regioselectivity of the intermolecular Diels-Alder reaction of acyl nitroso compounds (C-nitrosocarbonyl compounds) and nitrosoformates (O-nitrosocarbonyl compounds), J.
	www.scripps.edu /chem/boger/pubs.html (9399 words)

	Pubs to 1998 (Site not responding. Last check: 2007-10-09)
		Jones, J.P., Trager, W.F., Carlson, T.J. The binding and regioselectivity of reaction of (R)- and (S)-nicotine with cytochrome P-450cam: Parallel experimental and theoretical studies.
		J.P. Metabolism of 1,2-dichloro-1-fluoroethane and 1-fluoro-1,2,2-trichloroethane: Electronic factors govern the regioselectivity of cytochrome P450-dependent oxidation.
		Jones, J.P., Shou, M., Korzekwa, K.R. Predicting the regioselectivity and stereoselectivity of cytochrome P450-mediated reactions.
	joneslab.wsu.edu /pubs_1984-1997.htm (853 words)

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