the aldol reaction catalyzed by dna proline in water

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1、EarlystudiesrevealedthatL-prolinecouldcatalyzethedirectaldolreaction,butinmanycaseobtainingracemicproductinaqueousmedium.Moreover,consideringthatGolefesgroupreportedtheDNAbasedasymmetriccatalysis,DNAcouldinteractwithaminoacidsthroughHbond,whichwasconstituentpartofproteinorrecognizedasthesmal

2、lestproteininasymmetriccatalysis.WeassumethattheenantioselectivitycouldbeimprovedifthistypeofchiralacidservedasanadditiveintheL-prolinecatalyzedaldolreactions,duetoacooperativeeffectinthecatalyticsystem(Scheme1).Inthispaper,wereportanimprovedL-prolinecatalyzedaldolreactioninaqueousmedium.Und

3、ertheoptimizedconditions,thealdolproductwasaffordedinupto53%inaqueousmedium.Scheme1Table1TheAldolreactioncatalyzedbyDNA-prolineinwaterEntryDNA-proline(mmol)bYield%Ee%10.0389.7Rac.20.03212730.06263340.12243250.243828Reactionconditions:DNA:10mg,4-nitrobenzaldehyde:0.1mmol,H2O:1.5ml,acetone:1.

4、5ml,rtfor5d.a:noDNA.b:moleoftheproline.Table2TheeffectofwaterintheeefortheDNA-prolinecatalyzedaldolreactionofacetonewith4-nitrobenzaldehydeEntryH2O%Yield%Ee%Ee%a10767065225605393402342Rac.4502633Rac.5662834Rac.6751611Rac.Reactionconditions:DNA:10mg,L-proline:0.06mmol,4-nitrobenzaldehyde:0.1m

5、mol,rtfor5d.a:noDNATheeffectofwater-acetoneratioontheenantiomericexcessoftheproductwasalsoinvestigated(Table2).ThelowereesomuchasracemicproductwasobtainedinthepresenceofwatercatalyzedbyL-prolineonly,however,inthepresenceofDNA,itwasobtainedenantioselectiveproduct.Theeewasfrom53%to11%,accompan

6、yingwiththeratioofwaterfrom25%to75%(entry2-6).Inorganicmedium,thepresenceofDNAcouldalsoincreasetheeefrom65%to70%.ItwasdemonstratedthatDNAplayedanimportantroleinthealdolreactioninaqueousmedium.Table3TheeffectoftheconcentrationofthesubstrateandthecatalystEntrySubstrate(mmol)Yield%Ee%10.0313.82

7、0.1234230.2284140.331425a0.14141Reactionconditions:DNA:10mg,,H2O:1.0ml,acetone:1.5ml,rtfor5d.a:DNA:20mg.L-proline:0.12mmolTable4ThesourceofthechiralityEntryCatal.systemYield%Ee%1Proline+A93Rac.2Proline+T91Rac.3Proline+G88Rac.4Proline+C89Rac.Reactio