total synthesis and complete structural assignment of yaku’amide a

1、TotalSynthesisCompleteStructuralAssignmentofYaku’aeATakefumiKuranagaYusukeSesokoKomeiSakataNaoyaMaedaAtsushiHayataMasayukiInoueGraduateSchoolofPharmaceuticalSciencesTheUniversityofTokyoHongoBunkyokuTokyo1130033JapanSSupp

2、tingInfmationABSTRACT:Herewereptthefirsttotalsynthesisthecompletestereochemicalassignmentofyaku’aeA.Yaku’aeA(1)wasisolatedfromaspongeCeratopsionsp.asanextremelypotentcytotoxin.ItsstructurewasdeterminedexceptftheC4stereoc

3、hemistryintheNterminalacylgroup(NTA).Thistridecapeptideconsistsof2proteinogenic11nonproteinogenicaminoacidresiduesiscappedwithNTAaCterminalamine(CTA).αβDehydrovalineEZαβdehydroisoleucinesarethemostunusualnonproteinogenic

4、residuesof1necessitateddevelopmentofnewmethodologiesftheirassembly.ConsequentlyCumediatedcrosscouplingreactionswereefficientlyemployedfEZivesynthesesofthethreedipeptideswiththedehydroisoleucinesfconstructionofthetetrapep

5、tidewiththedehydrovaline.ThepeptidewasthenelongatedfromthetetrapeptideinastepwisefashiontodeliverthetwopossibleC4epimersof1.ExtensiveNMRstudiesrevealedthatthenatural1possessedtheC4SstereochemistrybiologicalassaysusingP38

6、8mouseleukemiacellsdemonstratedthatbothC4epimerspossessedcomparabletoxicities.Thepresentsyntheticmethodologiesfconstructionofthehighlyunsaturatedpeptidesequenceof1willallowstudiesoftherelationshipsbetweentheconfmationalp

7、ropertiesofdehydroaminoacidresiduescytotoxicity.■INTRODUCTIONMarinespongesarerichsourcesofstructurallyunusualbiologicallyactivepeptides.1Thesepeptidesexhibitavarietyofactivitiesincludinginsecticidalantimicrobialantiviral

8、antitumtumpromotiveantiinflammatyimmunosuppressiveactions.Someofthesecompoundshaveservedasdrugsasleadcompoundsindrugdevelopment2whileothershaveprovenusefulinstudiesdirectedtowardtheelucidationofbiochemicalpathways.Thissi

9、gnificantpharmacologicaldiversityisafunctionofpeptidestructureconfmationwhichareinturndictatedbythestructurallydiverseconstituentaminoacids.Thesepeptidescontainnotonlythe20canonicalproteinogenicLaminoacidsbutalsonumerous

10、nonproteinogenicaminoacidssuchasNCsubstitutedaminoacidsofeitherLDchiralityαβdehydroaminoacids.3In2010twolineartridecapeptidesyaku’aeAB(12Figure1)wereisolatedbyMatsunagafromadeepseaspongeCeratopsionsp.asextremelypotentcyt

11、otoxins.4ExtensiveNMRanalyseschemicalderivatizationstudiesrevealedtheentirestereostructuresof12exceptfthestereochemistryoftheC4methylgroupintheNterminalacylgroup(NTA).Yaku’aesconsistof2proteinogenic11nonproteinogenicamin

12、oacidresiduesarecappedwithNTAaCterminalamine(CTA).Thenonproteinogenicaminoacidsof1arecategizedintothreestructuralclasses:βhydroxyLaminoacids(residues17)Daminoacids(residues5681012)dehydroaminoacids(residues24913).Thepres

13、enceofαβdehydrovaline(residue13)E(residue4)Zαβdehydroisoleucines(residues29)isthemostunusualstructuralfeatureofyaku’aesbecausedehydrovalineEdehydroisoleucinehaveonlybeenfoundinseveralnaturalpeptidesZdehydroisoleucineisun

14、precedented.5AstheCCbondpreventsrotationofthesidechainthesefourunsaturatedaminoacidstogetherhavealargeimpactontheconfmationalbehavioftheirproximalresidues6therebypotentiallyinfluencingthebioactivethreedimensionalstructu

15、reoftheentiremolecule.7Thecytotoxicityassaysof1usingapanelof39humancancercelllines(JFCR39)8unveileditsdistinctgrowthinhibityprofileincomparisonto38clinicallyavailableanticancerdrugs.4Accdinglyexceptionalcytotoxicityapote

16、ntiallynewmodeofactionholdgreatpromisefthedevelopmentofyaku’aestheirrelatedstructuresasnoveltherapeutics.Howeverthenaturalsupplyof12hasbeenextremelylimitedpreventingdetailedinvestigationsoftheirbiologicalactivitiesaswell

17、asspectroscopicdeterminationoftheintrinsicthreedimensionalshape.Thehighlyunsaturatedpeptidestructureacteristiccytotoxicityprofilemotivatedustolaunchaprogramtowarddecipheringthechemicalbiologicalfunctionsofyaku’aesusingsy

18、ntheticganicchemistry.910Herewereptthedevelopmentofanewassemblymethodologyoftheαβunsaturatedaminoacidresiduesthefirsttotalsynthesisof1aswellasthestructuralelucidationoftheSstereochemistryoftheC4stereocenter.11■RESULTSDIS

19、CUSSIONWeplannedtosyntheticallyconstructthetwopossibleC4isomersofyaku’aeA(1a1bFigure1)thentospectroscopicallycomparethetwocompoundswiththenatural1fdeterminationoftheabsoluteC4stereochemistry.Received:February82013Publish

20、ed:March162013Articlepubs.acs.gJACS?2013AmericanChemicalSociety5467dx.doi.g10.1021ja401457h|J.Am.Chem.Soc.20131355467?5474synthesizedinageometrycontrolledfashion(Scheme2).Aconjugateadditionoflithiumdiethylcupratetoethyl2

21、butynoate32insitutrappingwithiodinedeliveredZolefin33.19Reductionof33withdiisobutylaluminumhydride(DIBALH)protectionoftheresultantallylicalcoholwiththetbutyldiphenylsilyl(TBDPS)groupfurnishedZalkenyliodide9.Throughthesam

22、etwostepprocedureEalkenyliodide11wasproducedfrom35whichresultedfrom14additionoflithiumdimethylcupratetoethyl2pentynoate34.Thegeometriesofthedoublebondsof911wereunambiguouslyconfirmedbynuclearOverhausereffect(NOE)experime

23、nts.AfterscreeningcouplingconditionsftheC(sp2)NbondfmationtheBuchwaldreagentsystem[CuINN′dimethylethylenediamine(36)Cs2CO3]20wassuccessfullyemployedfconstructionofthethreeenaes(Scheme3).Howeveramountsofthereagentssolvent

24、concentrationhadtobecarefullytunedtoobtainhighyieldingtransfmations.WhenNtbutoxycarbonyl(NBoc)glycinae10Ealkenyliodide11(1.2equiv)weretreatedwithCuI(30mol%)36(2equiv)Cs2CO3(1.2equiv)indioxane(1M)at70CthehinderedC?Nbondwa

25、sstereoivelyfmedtoaffdEenae37in96%yield.Dioxanewasusedinthisreactioninsteadofmecommonsolvents(e.g.tolueneTHF)indertorealizehighconcentrationsofthesubstratesbecausedilutionresultedinsignificantlyloweryields.Furtherapplica

26、tionoftheseoptimizedconditionsenabledthecouplingreactionsoftheprimaryaesproximaltothestericallyencumberedtetrasubstitutedβcarbonsof815.21TheCucatalystCs2CO3promotedstereoivesubstitutionofiodineofZalkenyliodide9withthepri

27、maryaesof815givingrisetothecrespondingZenaes39(87%yield)41(88%yield)respectively.Thesestereoiveconstructionsofthethreehinderedtetrasubstitutedolefins373941undermildconditionsdemonstratedtheversatilityofthepresentprotocol

28、.ThebisBocprotecteddipeptidefragments435weresynthesizedfrom373941respectivelybyapplyingthesamesixstepsequence(Scheme3).Enae373941wastreatedwithTBAFtoprovidethecrespondingallylicalcoholwhichwasoxidizedtocarboxylicacid3840

29、42bysequentialreactionsusingSO3pyridineDMSODess?Martinreagent22NaClO2.23NexttheadditionalBocgroupwasintroducedtothesecondaryaeof384042bythestardprotectivegroupmanipulations.Allylesterfmation(allylbroeCs2CO3)from384042che

30、moiveattachmentoftheBocgroupattheenaenitrogen(Boc2OEt3NDMAP)removaloftheallylgroup[Pd(PPh3)4mpholine2methyl2butene]24gaverisetotherequisitecompound435.Scheme2.StereoiveSynthesesofEZAlkenylIodideMonomersaaDIBALH=diisobuty

31、laluminumhydrideNOE=nuclearOverhausereffect.Scheme3.StereoiveSynthesesofEZDehydroisoleucineMoietiesaaTBAF=tetranbutylammoniumfluidetBu=tbutylAlloc=allyloxycarbonylPh=phenylDMF=NNdimethylfmaePy=pyridine.JournaloftheAmeric