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1、TECHNICALBULLETINCleavage,Deprotection,andIsolationofPeptidesafterFmocSynthesisCleavageanddeprotectionisoneofthemostcrucialPotentialProblemsstepsinpeptidesynthesis.Thetreatmentofapeptidyl-resinwithacleavagecocktailisnotonesimpleCertainaminoacidscancauseproblemsduringTFAreaction,butaseriesofcomp
2、etingreactions.Unlesscleavageanddeprotection.Thesefallintothreebroadsuitablereagentsandreactionconditionsareselected,categories:thepeptidecanbeirreversiblymodifiedordamaged.1.AminoacidswhoseprotectinggroupsareeasilyThegoalofcleavage/deprotectionistoseparatetheremoved,butwhosedeprotectedside-cha
3、insarepeptidefromthesupportwhileremovingtheprotectingespeciallylabileinacidconditions(e.g.,Met,Cys,groupsfromtheside-chains.ThisshouldbedoneasHis,Trp).quicklyaspossibletominimizetheexposureofthe2.Aminoacidswhichneedmorethanthenormaltwopeptidetothecleavagereagent.Thepeptideisthenhoursforcomplete
4、removaloftheside-chainrecoveredfromthereactionmixtureandanalyzed.Thisprotectinggroups(e.g.,Arg(Pmc/Mtr),technicalbulletindescribesproceduresforcleavageofAsn/Gln(Mbh)).peptidesfromsolidsupportsassembledviaFmoc/tBu-3.Aminoacidswhoseside-chainprotectinggroups,1basedstrategies.onceremovedfromthesid
5、e-chain,areextremelyreactiveandmustbescavengedtopreventTherearenumerousproceduresintheliteraturewhichreattachmentormodificationofthedeprotecteddescribeavarietyofcleavageanddeprotectionside-chains(e.g.,Arg(Pmc/Mtr),methodsforpeptidessynthesizedwithanFmoc/tBuAsn/Gln(Tmob)).2-4strategy..Mostofthes
6、etechniquesareTFA-based,andtheydifferprimarilyinthefinalconcentrationofTFA,typesofscavengersused,andreactiontimes.Table1:Side-chainProtectingGroupsforFmocAminoSomeofthevariablityinmethodsreflectstheAcidspreferencesofindividuallabs,butitismainlydictatedAminoProtectingGroupFunctionalitybytheamino
7、acidcompositionofthepeptide.acid(boldisProtectedrecommended)Someaminoacidshavepotentiallyreactiveside-chainsAla(A)nonewhichgeneratecarboniumionsandotherreactiveArg(R)Pbf,Mtr,PmcguanidinoNspeciesduringTFAcleavageofthepeptidefromthe
