DOC

Prediction of the ^13C NMR Chemical Shifts of Stilbene Analogues by GIAO Method

By Jeanne Boyd,2014-12-25 03:14
10 views 0
Prediction of the ^13C NMR Chemical Shifts of Stilbene Analogues by GIAO Method

    Prediction of the ^13C NMR Chemical

    Shifts of Stilbene Analogues by GIAO

    Method

    CHEM.RES.CHINESEUNIVERSITIES2010,26(6),10161019

    Predictionofthe3CNMRChemicalShiftsof

    StilbeneAnaloguesbyGIAOMethod

    ^

    XIEHuiding,LIY_u-peng.,QIUKaixiong,LIUBoandCHENYa-ping

    DepartmentofChemistry,SchoolofPharmaceuticalSciences,KunmingMedicalCollege.Kunming65o5Oo.R.China

    AbstractAfterthegeometryoptimizationatB3LYP/6.31+Gflevel,thecalculationsoftheNMRchemical

    shiftsofaseriesofstilbeneanalogueswerecarriedoutbymeansofGaugeIncludingAtomicOrbitals(GIAO)method

    atHF/6.31+G(levelandB3LYP/6.311G+(2p)level,respectively.The"CNMRchemicalshiftscalculatedat

    bothHF/6.3l+G(andB3LYP/6

    31+Gf)levelsareinagreementwiththeobservedvalues.Byvirtueofaseries oflinearcorrectionequationS(Jpred=a+b~calcd)ofthe"Cchemicalshifts,accuratepredictionof"Cchemicalshifts

    wasachievedforthenewstilbenecompounds.Forthe"CNMRchemicalshiftscalculatedatHF/6.31+G(Ievel,

    thelinearcorrelationof~predwith~expt1.

    isexcellent,andthesquareofcorrelationcoefficient,r,is0.9985.The maximumabsolutedifferencebetweenr{predandxDIl,

    ?,is2.3,andtheroot-mean-squareerrorbetweenredand

t~expt1.

    is0.98.Inthemeantime,forthoseobtainedatB3LYP/6

    3l+G(d,p)level,thelinearcorrelationofd.with Ynt1iSalsoexcellent,andthesquareofcorrelationcoefficient,r,isuptO0.9987.Themaximu

    mabsolutedifierence

    between5predand~exptl,

    ?,is2.2,andtheroot-mean-squareerrorbetweent~predand6]expt1.

    isonly0.88.

    KeywordsStilbeneanalogue;"CNMRchemicalshift;Prediction ArtieleID1005.9040(20101.06.1016.04

    1Introduction

    NMlRhasbecomeastaplemethodologyforthe determinationofmolecularstructuresofnewlysyn. thesizedmolecules,intermediates,orspeciesobtained fromnaturesources.Despitethegreatadvancementin NMtechnique.inordertocharacterizeanunambi. guousmoleculestructure.westillneedtoolstoaccu

    rarelypredictNMRspectra.Theoreticalcalculation hasbeenusedtoaidtheinterpretationofN??data

    formorethanadecadeL.Recently,therehasbeen increasinginterestintheuseofabinitioNMRche

    micalshiftpredictiontoaidstructureassignmentsjJ_

    Stilbeneanaloguesareatypicaltypeofcom

    poundsspecialforgenusPholidotaandGnetum. Pharmacologicalstudieshaveshownthatstilbenes displayinhibitoryeffectsonnitricoxideproduction'

    Uptonow,sevenstilbeneanalogueshavebeeniso

    latedandtheirstructureshavebeenelucidatedalsobv NMRspectra.whichareresveratrol(1),trans

3,3,5-trihydroxystilbene(2),trans-2,3,3'-trihydroxy

    5-trimethoxystilbene(3),trans3hydroxy-2,3,5-tri-

    methoxystilbene(4),trans3,3'-dihydroxy-2,5-dime?

    thoxystilbene(5),trans-3,4'-dihydroxy-2,3,5trime

    thoxystilbene(6)andtrans-3,3'-dihydroxy-2,4,5tri-

    methoxystilbene(7)t,引.buttothebestofourknow.

    1edge.theNMRchemica1shiftcalculationsofthese compoundscannotbefound.Intherecentwork,Guo andhercoworkershaveisolatedanewstilbenealia- loguenamedtrans3,3',5trihydroxy2'-methoxystil

    bene.Inordertoconfirmthestructureofthisnew compound,thequantumchemistrycomputational methodwasusedtopredictits"CNMRchemical shifts.Aseriesofstilbeneanalogueswaschosento perforn1NMRchemicalshiRcalculationbyGauge IncludingAtomicOrbitals(GIAO)methodatdifferent levelsoftheory.Wefocusedourmindsonestablishing anecientwaytopredictthe"CNMRchemical

    shiftsofstilbeneanaloguesaccurately.W_eexpected thatthetheoreticalresultscanoffersomeusefu1ref- erencesforthestructureassignmentofnewstilbene analogues.

    2ComputationalMethods

    Thestudiedcompoundsjnthisworkwerease- riesofstilbeneanalogues【一.whosestructuresare

    showninFig.1.andtheirexperimentalNMlRdata usedinthisstudyarethe"Cchemicalshiftsthein- temalstandardcompoundofwhichistrimethyl

    silyl(TMS).Thecorrespondingvaluesarelistedin Correspondingauthor.E-mail:liyupeng26@126.corn

    ReceivedNovember30,2009;acceptedFebruary10,2010. SuppoSedbytheScientificResearchFoundationofDepartmentofEducationofYunnanProv

    ince,China(No.09Y0181)

    NO.6XIEHui?dingetal1O17

    TablelandTlable2

    Ra

    1:R2=R3=H,R'4=OH

    2:R2=R4=HRs=OH

    H

    H

    R

    3:R2=R3=OH.R'4=H

    4:R2=R3=OCH3.R4=H

    5:R2=OCH3,R3=OH,R4=H

    6:R2=R3=OCHR'4=OH

    Newcompound

    H

    H

    7:R2=R4=OCH3.R3=OH

    Fig.1Structuresofstilbeneanalogues

    Table1Comparisonbetweenthecalculated(HF)andexperimentalCNMRchemicalshiftsfo

    rcompounds17

    Table2Comparisonbetweencalculated(DFT)andexperimentalCNMRchemicalshiftsforc

    ompounds17

    poundswerebuiltbyHyperchemsoftware.Toobtain thelowestenergyconformationsofthemolecules,all theconformationalsearcheswereperformedby

    9]withmolecular Hyperchemprogram(Version7.51

    mechanicsmethod.Basedonthelowestenergycon- culeswereperformedat

withquantumchemistry

    B3LYP/6-3l+G(d,p)level

    method.TheCNMR

    chemicalshifts(TMSasinternalstandard)ofthe0pti

    mizedstructureswerecalculatedatHF/63l+G(

    levelandB3LYP/6-311G+(2d,p)levelrespectivelyby 1018CHEM.RES.CHINESEUNIVERSITIESVb1.26 GIA0method[o.AI1mequantumchemicalcaI

    culationswereperformedwiththehelpofGaussian 03softwarepackage.

    II1addition.thelinearregressionanalysesforex. perimentalandcalculated"CNMRchemicalshiftsof thecompoundswerecarriedoutwiththeaidofsoft

    wareMicrosoftOfficeExcel2003.

    3ResultsandDiscussion

    BecausetIleconformationsofstilbeneanalogues arerigid.thelowestenergyconformersobtainedby conformationalsearcharethemainconformers13,14.

    Aftergeometryoptimizationsofthestudiedcom. pounds'lowestenergYconformations.whichwere performedatB3LYP/6-31+G()level,werecom. pleted.the"CN?chemicalshifts(TMSasintemal

    standard)werecalculatedatHF/6-3l+G(leveland B3LYP/6-3l1G+(2d,p)levelrespectivelybyGIAO memod.Boththe"CNM_Rchemicalshiftscalculated atHF/631+G(1evelandthosecalculatedat

    B3LYP/6.31+G()levebyGIAOmethodwerein

    agreementwiththecorrespondingexperimentalvalues Thecomparisonbetweenthecalculated"CNMR

chemicalshiftatHF/63l+G(levelandexperimen

    tal"CNMRvalue(TMSasinternalstandard)forthe sevenstilbeneanaloguesisshowninlble1.andthe comparisonbetweenthecalculated"CN??chemi.

    calshiRatB3L,YP/6-3llG+(2)levelandexperi. mental"CNM_Rvalueforthecompoundsisshownin Table2.

    AscanbeseenfromTlablelandTable2.both

    the"CNMRchemicalshiftsobtainedatboth

    HF/6-3l+G(andB3LYP/63l+G()levelswere

    basicallyinagreementwiththeexperimentalvalues, buttheywerenotveryaccurate.Forcompound1,the root-mean.square(rms)errorsbetweencalculatedand experimental"Cchemicalshiftswere5.2(HF)and 6.I(DFT),respectively.Thermserrorsofcompound2 werefoundtobe4.2and6.6.respectively.Similarly, therillserrorsofcompound3wereobservedat3.5 and6.1.respectively,thoseofcompound4werelo- catedat4.4and6.2,respectively,thoseofcompound 5wereat4.1and6.0.respectively,andthoseofcorn

    pound6wereat6.4and7.7,respectively,andfinally, thoseofcompound7wereat6.4and4.7,respectively. Inordertoimprovethepredictiveaccuracyofthe "CNM_Rchemicalshiftsforstilbeneanalogues.our approachinthispaperistouselinearregressiondata toprovidealinearcorrectionforthecalculated "CN~?chemicaIshifts.Accordingtothecalculated andexperimental"CNMRchemicalshiftsofthe sevencompounds,aseriesoflinearcorrectionequa- tions(red.=a+bfica1cd.)forpredictingthechemical

    shiftsofdirentcarbonatomsinthemoleculesof stilbeneanalogueswereobtainedwithsoftwareExcel 2003.whicharelistedinT{lble3andble4.The

    comparisonbetweenthepredicted"CNRchemical

    shiftcalculatedatHF/631+G(level(c~.1cd.)andex-

    perimental"CNMRchemicalshift(Sexpt1.)fort}lenew compoundisshowninTable3.andthecomparison betweenthepredicted"CNMRchemicalshinob. tainedatB3LYP/6-3l1G+(2d,p)level(fic~cd.)andex- perimental"CNMRchemicalshiR(ext1.)forthenew

    compoundisshownin1,able4.

    Table3Comparisonbetweenthepredieted(HF)and experimentalCNMRchemicalsh~ftsfor

    thenewcompounds

    =d+6cald,

    A;cd1.

    Table4Comparisonbetweenpredieted(DFT)and experimental.CNMRchemicalshiftsfor

    thenewcompounds.

    =ct+b3calcd,A6=6predxpu.

    ASCanbeseenfromTable3andTable4,both thepredictedchemicalshiftscalculatedwithHFand No.6XIEHui-dingetall019

    DFTmethodsareinquitegoodagreementwith experimentaldata.Thecorrelationbetweendpred (calculatedwithHFmethod)andexDt1.isshownin Fig.2.Thelinearcorrelationbetweendprcd. and~expt1.

    is

    excellent.andthesquareofcorrelationcoe~cient,,

    is0.9985.Themaximumabsolutedifferencebetween predictedandexperimentalshifts,Aft=dprcd.

    e)(Dt1.,is

    2.3.andtherootmeansquare(rms)errorbetween

    predictedandexperimentalshiftsis0.98.Inthemean

    time,thecorrelationbetweendpred.(obtainedwithDFT method)andxntI_isshowninFig.3.Thelinearcorre

    1ationbetweendpred.

    and~expt1.

    isalsoexcellent,andthe

    squareofcorrelationcoefficient.rz.isupto0.9987. Themaximumabsolutedifferencebetweenpredicted andexperimentalshifts,Ad6~pred.

    -

    6e?)t1.,

    isonly2.2,

    andtherrnserrorbetweenpredictedandexperimental shiftsisonly0.88.

    

    Fig.2PlotofexperimentalCNMRchemicalshifts .predicted.CNMRchemicalshifts(HF)for thenewcompound

    

    red

    Fig.3Plotofexperimental3CNMRchemicalshifts ps.predictedCNMRchemicalshifts(DFT) forthenewcompound

    4Conclusions

    TheNMRchemicalshiftcalculationsofaseries

    ofstilbeneanalogueshavebeencarriedoutbyGIAO methodatHF/63l+G(levelandatB3LYP/

    6-311G+(2d,p)level,respectively.Itwasfoundthat boththe.CNMRchemicalshiftscalculatedat HF/6.3l+GflevelandthosecalculatedatB3L,P/ 6311G+(2d,p)levelarebasicallyinagreementwith theobservedvalues.Inordertopredictthe"CNM|R chemicalshiftsofstilbeneanaloguesaccurately,ase

    riesoflinearcorrectionequationS(dpred.一口+6a1cd.)for

    predictingthe?CNMRchemicalshiftsofstilbene

    analoguemoleculeswereobtained.Forthenewcom

    pound,thepredictedchemicalshiftsareinquitegood agreementwithexperimentalvalues.Thelinearcorre- lationbetweendpred.[calculatedatHF/63l+G(level

    and~expt1.

    isexcellent,andthesquareofcorrelation coecient.r.is0.9985.Themaximumabsolute differencebetweendpred.

    and6~expt1.,

    Aft,is2.3,and

    thermserrorbetweendpred.

    andxDt1.

    is0.98.The1i

    nearcorrelationbetweendpred.

    [obtainedatB3LYP/

    63l1G+(2d,p)leveland~expt1.isalsoexcellent,and thesquareofcorrelationcoemcient.rz.isupto0.9987 ThemaximumabsolutedifferencebetweenJpred. and

    expt1.,Ad,is2.2,andtherlTISerrorbetweendprcd.

and

    ~expt1.

    isonly0.88.Therefore,wecouldconfirmthat thestructureassignmentofthenewcompoundisrea

    sonable,andwehopethattheabovemethodcould offersomeusefulreferencesforthestructureassign

    mentofothernewstilbeneanalogues.

    References

    1NevinsN.,CiceroD.,SnyderJ.E,Org.Chem.,1999,64,3979 2]StahlM.,ScopferU.,FrenkingG,HoffmannR.w,Org.Chem [3

    [4

    5

    6]

    7

    [8

    9

    0

    l

    2

    [13]

    l4]

    1997,62,3702

    BifulcoG.,DambruosoE,Gomez-PalomaL.,RiccioR,Chem.Rev.,

    2007,107,3744

    GuoX.Y,WangJ.,WangN.L.,KitanakaS.,LiuH.W,YaoX.S., Chem.Pharm.Bul1.,2006,54(1),21

    GuoX.Y.,WangJ.,WangN.Ll,KitanakaS.,YaoX.S.,Chin.Tradit

    HerbDrug.,2006,37(4),492

Report this document

For any questions or suggestions please email
cust-service@docsford.com