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Topic: Diastereomer


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  Diastereomer - Wikipedia, the free encyclopedia
Diastereomers are stereoisomers that are not enantiomers, or mirror images of each other.
The families of 5-6 carbon carbohydrates contain many diastereomers because of the large numbers of asymmetric centers in these molecules.
Diastereoselectivity is the preference for the formation of one or more than one diastereomer over the other in an organic reaction.
en.wikipedia.org /wiki/Diastereomer   (240 words)

  
 Encyclopedia topic: Diastereomer   (Site not responding. Last check: 2007-10-13)
Diastereomers are stereoisomer (additional info and facts about stereoisomer) s that are not enantiomer (Either one of a pair of compounds (crystals or molecules) that are mirror images on each other but are not identical) s or mirror images of each other.
The families of 5 and 6 carbon sugar (A white crystalline carbohydrate used as a sweetener and preservative) s contain many diastereomers because of the large numbers of asymmetric centers in these molecules.
See carbohydrates (An essential structural component of living cells and source of energy for animals; includes simple sugars with small molecules as well as macromolecular substances; are classified according to the number of monosaccharide groups they contain).
www.absoluteastronomy.com /encyclopedia/d/di/diastereomer.htm   (190 words)

  
 Diastereomeric Control in the Formation of Carbon-Cobalt Bonds in Organocobalt Corrinoids: Reactions of Cobalt(II) ...
diastereomer is shown to be the result of the differential side chain configurations at the
diastereomer in the product is increased to 95% and the effect is entirely entropic again.
Taken together with previous work, the results lead to a general picture of the energetics of alkyl radical + cobalt(II) corrinoid combination reactions and their microscopic reverse, the homolytic dissociation of carbon-cobalt bonds, a rare instance in which the subtleties of such diastereomeric control can be understood at a very fundamental level.
pubs.acs.org /cgi-bin/abstract.cgi/inocaj/1997/36/i09/abs/ic9614273.html   (375 words)

  
 Addition of a chiral non-racemic silyloxypyrrole to an activated 1,4-benzoquinone   (Site not responding. Last check: 2007-10-13)
The resonance assigned to H-1' in diastereomer 5 was not broad as was observed in the less polar diastereomer 6, resonating as a doublet of doublets (J
The distance between H-8b and the closest ortho hydrogen in the phenyl ring is 4.7 Å, and the distance between H-8b and H-1' is 2.6 Å.
In this model, the distance between H-8b and the closest ortho hydrogen in the phenyl ring was 3.0 Å, and the distance between H-8b and H-1' is 2.8 Å.
www.arkat-usa.org /ark/journal/2002/I01_General/2-384E/384E.asp   (2660 words)

  
 Alkylamino-furanon-derivatives - Patent 4725617
In the compound of the formula (II) used as starting material the chiral carbon atoms are of S-configuration in all the three amino acid portions, the steric arrangement of the hydroxyl group may be of R or S configuration.
If the diastereomers of the formula (II) are not separated, then a mixture of the diastereomers of the compound of the formula (I) is obtained after cyclizing, where the desired diastereomer can subsequently be separated from.
If a mixture of the diastereomers of the compound of the formula (II) is used as starting material, then it depends on the reaction medium whether the compound of the formula (I) thus obtained is a mixture of diastereomers or only one diastereomer is formed.
www.freepatentsonline.com /4725617.html   (3797 words)

  
 Stereochemistry Tutorial
The easiest way to tell apart an enantiomer and a diastereomer is to look at whether or not the compounds are mirror images of each other.
A is a pair of diastereomers, because the configuration is S, S in the first compound and R,S in the second compound.
Diastereomers occur when the compounds have the same chemical formula, but are not mirror images of each other.
facultystaff.vwc.edu /~jeaster/courseinfo/Tutorials/stereochemistryl.html   (1258 words)

  
 Assymetric Induction
Stereoselectivity refers to the preferential formation in a chemical reaction of one product stereoisomer (enantiomer or diastereomer) over another, as a result of inherent reaction specificity, or the influence of chiral features in the substrate, reagent, catalyst or environment.
Transition states leading to diastereomers C and D are drawn at the bottom of the diagram.
The facial bias imposed on the aldehyde carbonyl group by a β-polar substituent may be seen in the proportions of diastereomers having 1,3-anti (β:δ-anti) configurations (e.g.
www.cem.msu.edu /~reusch/VirtualText/sterslct.htm   (8654 words)

  
 [No title]   (Site not responding. Last check: 2007-10-13)
In other embodiments, the diastereomers may be present in such a manner wherein the composition does not form a racemic mixture.
These diastereomers may be present in amounts such that the composition forms a racemic mixture, or alternatively, these diastereomers may be present in amounts such that the composition does not form a racemic mixture.
In other embodiments, such diastereomers may be present in such a manner wherein the composition does not form a racemic mixture.
www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/14367.010301&ELEMENT_SET=DECL   (6973 words)

  
 Andrew M. Goldsweig's Diastereomer Page   (Site not responding. Last check: 2007-10-13)
Diastereomers are divided into two main classes based upon the nature of their spacial differences:
Meso compounds are superimposable upon their mirror images since these images can be rotated 180 degrees to match the original compounds.
Since they are not enantiomers, meso compounds are classified as diastereomers.
www-personal.umich.edu /~dgoldswe/mit/dcds/diastereomers.html   (227 words)

  
 Derivatives and precursors of captopril and its analogues - Patent 5237073   (Site not responding. Last check: 2007-10-13)
A mixture of diastereomers is referred to as a diastereomeric mixture, where as the term is used herein the diastereomers may be present in any proportion.
Synthesis of compounds with asymmetric centers by standard organic synthetic techniques generally leads to a racemic or diastereomeric mixture which, in the aggregate, may have a relatively low specific bioactivity since certain of the stereoisomers in the mixture are likely to be biologically inactive.
The amide compounds which are the primary subject matter of this invention contain two chiral centers wherein one of the chiral centers is located alpha to the carboxyl carbon in the thiol alkanoyl segment of the amide and the other chiral center is alpha to the nitrogen which forms the amide.
www.freepatentsonline.com /5237073.html   (8455 words)

  
 Cyclosaligenyl-2',3'-didehydro-2',3'-dideoxythymidine Monophosphate: Efficient Intracellular Delivery of d4TMP -- ...
Diastereomer of cycloSal-d4TMP in CEM Cells in Function of Incubation Time.
diastereomers was exposed to the CEM cell cultures.
The cyclosaligenyl prodrugs consist of two diastereomers that are eluting at a close distance to one another on HPLC.
molpharm.aspetjournals.org /cgi/content/full/58/5/928   (4513 words)

  
 cyclohexane conformations
This is true even though the ring is not actually planar but rather has chair conformations.
Enantiomers: B and C Diastereomers: A and B, A and C
The cis diastereomer consists of one pair of enantiomeric conformers.
www.elcamino.cc.ca.us /Faculty/jshankweiler/new_page_2.htm   (290 words)

  
 In Vitro Activity and Potency of an Intravenously Injected Antimicrobial Peptide and Its DL Amino Acid Analog in Mice ...
The diastereomer at its MIC was added to bacteria or spheroplasts that had been preequilibrated with the fluorescent dye diS-C
Fluorescence recovery was measured 1 to 120 min (at 5-min intervals) after the diastereomer was mixed with the bacteria, and its maximum was recorded.
The consequence of sequence alteration of an amphipathic alpha-helical antimicrobial peptide and its diastereomers.
aac.asm.org /cgi/content/full/48/8/3127   (1777 words)

  
 101702g3540 - Quiz - Organic Chemistry 3540 - October 17, 2002 - Dr. Sundin - UWP   (Site not responding. Last check: 2007-10-13)
_____ A diastereomer of B is: A; C; D; or None of the above.
Both A and C are diastereomers of A.
Also note that A and C are identical so B actually has only one diastereomer.
www.uwplatt.edu /~sundin/354-2/5421017g.htm   (173 words)

  
 Resolution of Phenylsuccinic Acid   (Site not responding. Last check: 2007-10-13)
The salt is a mixture of two diastereomers (S,R and S,S).
Each diastereomer has different solubilities in a particular solvent, and the less soluble diastereomer will precipitate.
The precipitate of the less soluble diastereomer, which contains the (S)-(+) acid, is filtered and the optically active phenylsuccinic acid is recovered by the addition of HCl.
acad.udallas.edu /chemdept/hendrickson/3121/resolution_phenylsuccinic_acid.htm   (344 words)

  
 draw_enant.html   (Site not responding. Last check: 2007-10-13)
Discussion: For the same reasons as it is important to recognize and classify stereoisomers it is valuable to be able to draw enantiomers and diastereomers as well.
Once again, you may wish to verify the answer by labeling the stereocenters of the mirror image molecule as R or S. Drawing diastereomers: Recall that stereoisomers differ in the position of the atoms in space, and that diastereomers are stereoisomers that are not enantiomers.
Some thought on this will suggest that we can draw the diastereomer of a given structure by inverting one or more, but not all of the stereocenters.
web.chem.ucla.edu /~harding/tutorials/stereochem/draw_enant.html   (352 words)

  
 DigitalCommons@University of Nebraska - Lincoln | The diastereoselective synthesis of 1,2-dioxanes and 1,2,4-trioxanes ...
Cyclization was originally postulated to proceed through a pseudo chair transition state, established by the substituents therein.
Synthesis of 1,2-dioxanes proceeded with moderate selectivity for the cis-3,6-dialkyl diastereomer (B), which can be linked to bias in the transition state.
Equilibration of a mixture of diastereomers (A and B) with acidic methanol afforded a 3:1 mixture enriched in the trans-3,6-dialkyl-1,2-dioxane diastereomer, in which both alkyl groups occupy equatorial positions.*
digitalcommons.unl.edu /dissertations/AAI9908467   (398 words)

  
 [No title]   (Site not responding. Last check: 2007-10-13)
The chlorines are green and the hydrogens on the chirality centers are red.
This is a diastereomer of the two stereoisomers above because it has the same configuration at one chirality center and the opposite configuration at the other.
It has a plane of symmetry that bisects the bond between the two carbons of the chirality centers.
www.du.edu /~jhornbac/organic/diclbutane.html   (250 words)

  
 [No title]   (Site not responding. Last check: 2007-10-13)
This means that you'll draw the structure of the salt on the spectrum, label all hydrogens and corresponding peaks (cross-referenced to one another), and identify splitting patterns.
Using the integrals, calculate the percentages of each diastereomer in the sample.
that show the differences in integration between the two diastereomers.
www.naz.edu:9000 /~organic/fall/fallorganic/labstuff/LFUexp7.htm   (496 words)

  
 [No title]
In order to separate enantiomers, they must be temporarily converted to a diastereomer.
  Then convert the diastereomers back into their original compounds in separate containers.
The solubility of the diastereomers in methanol is different.
www.ipfw.edu /chem/261/261Fall03/261nt02i.htm   (395 words)

  
 Chem2O06 - 1997/98 - Experiment 7
In this experiment you will convert a chiral alcohol into its chiral diastereomer using a scheme involving oxidation to the ketone followed by stereoselective reduction to the diastereomer using sodium borohydride:
In camphor, however, the top and bottom faces of the carbonyl group are different, and we will attempt to take advantage of this to selectively reduce the ketone to the other diastereomer of the alcohol.
Inspection of a molecular model of camphor will reveal that the exo face is considerably more sterically hindered than the endo face, due to the presence of one of the geminal methyl groups.
www.chemistry.mcmaster.ca /~chem2o6/labmanual/expt7/2o6exp7.html   (806 words)

  
 Suppression of Human Prostate Tumor Growth in Mice by a Cytolytic D-, L-Amino Acid Peptide: Membrane Lysis, Increased ...
acids lytic peptide and its diastereomer, both of which are
Papo N, Shai Y. New lytic peptides based on the D, L amphipathic helix motif preferentially kill tumor cells compared with nornal cells.
Oren Z, Shai Y. Selective lysis of bacteria but not mammalian cells by diastereomers of melittin: Structure-function study.
cancerres.aacrjournals.org /cgi/content/full/64/16/5779   (4225 words)

  
 Chromatography Forum
i am working on a synthetic diastereomers from medicinal chemistry project, the usual C18 or phenyl-hexyl column for separation for marfey's derivatization for carboxylic acid to amide diastereomers does'nt work here.
They are supposed to be good for the separation of diastereomers.
I suggest the change of pH, and use low solvent ratio in the mobile phase.
www.lcresources.com /discus/messages/5133/2353.html?FridayApril520020158am   (525 words)

  
 kinetic resolution@jmg
We have found that kinetic resolution of the alkenes 1 provides a route to novel chiral diols (3 or 4) in high optical purity.
From the four possible diastereomers, achiral dihydroxylation provides only a single diastereomer derived from only one of the two enantiomeric pairs of alkenes (i.e.
alkene 2 is completely unreactive!), and the same diastereomer is obtained by AD reactions.
homepage.mac.com /johngardiner/JMG_research/research/asymmetry.html   (632 words)

  
 Bromine Addition to Alkenes   (Site not responding. Last check: 2007-10-13)
A priori, we consider it possible that either diastereomer of the starting material should give all possible stereoisomers of the product.
Since the product has two chiral centers, four stereoisomers are possible: two pairs of enantiomers, which are diastereomers of each other.
We know that diastereomers behave differently, so we also should expect a different result for each diastereomer of the starting material.
chemistry.umeche.maine.edu /CHY251/Br2Add.html   (307 words)

  
 O-Glucuronidation of the Lung Carcinogen 4-(methylnitrosamino)-1- (3-Pyridyl)-1-Butanol (nnal) by Human ...
Previous studies have demonstrated that the major NNAL-Gluc diastereomer observed in the urine of snuff users was NNAL-Gluc
abundant NNAL-Gluc I diastereomer observed in the urine of snuff
(present study), where NNAL-Gluc II was the predominant diastereomer.
dmd.aspetjournals.org /cgi/content/full/28/11/1352   (6257 words)

  
 Technical Paper   (Site not responding. Last check: 2007-10-13)
Applications to the synthesis of racemic indolizidine 209B and its (5R*,8S *,8aS *)-(±) diastereomer, and to (-)-indolizidine 209B
Syntheses of racemic (5R*,8R*,8aS *)-8-methyl-5-pentylindolizidine (indolizidine 209B) (±)-1 and its hitherto unknown (5R*,8S *,8aS *) diastereomer (±)-20 were accomplished in eight steps from pyrrolidine-2-thione and ethyl oct-2-enoate.
Pu2Pu.com is not responsible for the availability of such external sites or resources, and does not endorse and is not responsible or liable for any Content, advertising, products, or other materials on or available from such sites or resources.
www.pu2pu.com /htdocs/paper_niveau2.asp?ref=453063279   (178 words)

  
 Anthracycline chemistry
Obviously, the steric hindrance from the sugar reduces underside attack.
Therefore the major diastereomer in these schemes results from the favoured approach above and the minor diastereomer (seperable by fractional crystallisation) from a direction below the conjugated double bonds.
The Diels-Alder reaction (in cool acetone) occurs with about 71% diastereomeric excess; the major diastereomer (8) is isolated in 74% yield.
www.jonathanpmiller.com /Anthracycline_chemistry.htm   (1573 words)

  
 [No title]   (Site not responding. Last check: 2007-10-13)
Enantiomer — Flip ALL stereocenters; Diastereomers — Flip at least one but NOT all stereocenters.
Draw any diastereomers of the above molecules as well.
Are any of these diastereomers a meso compound?
www.stanford.edu /~jakelai/chem33/stereosol.doc   (762 words)

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