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1、PrefaceTheuseofenzymes–employedeitherasisolatedenzymes,crudeproteinextractsorwholecells–forthetransformationofnon-naturalorganiccom-poundsisnotaninventionofthetwentiethcentury:theyhavebeenusedformorethanonehundredyears.However,theobjectofmostoftheearlyresearchwastotallydifferent
2、fromthatofthepresentday.Whereastheelucidationofbiochemicalpathwaysandenzymemechanismswasthemaindrivingforcefortheearlystudies,incontrastitwasmainlyduringthe1980sthattheenormouspotentialofapplyingnaturalcatalyststotransformnon-naturalorganiccom-poundswasrecognized.Thistrendwaspar
3、ticularlywellenhancedbytherecommendationoftheFDA-guidelines(1992)withrespecttotheuseofchiralbioactiveagentsinenantiopureform.Duringthelasttwodecades,ithasbeenshownthatthesubstratetoleranceofnumerousbiocatalystsisoftenmuchwiderthanpreviouslybelieved.Ofcourse,therearemanyenzymeswh
4、ichareverystrictlyboundtotheirnaturalsubstrate(s).Theyplayanimportantroleinmetabolismandtheyaregeneral-lynotapplicableforbiotransformations.Ontheotherhand,animpressivenumberofbiocatalystshavebeenshowntopossessawidesubstratetolerancebykeepingtheirexquisitecatalyticpropertieswithr
5、especttochemo-,regio-and,mostimportant,enantio-selectivity.Thismadethemintothekeytoolsforbiotransformations.Asaresultofthisextensiveresearchduringthelasttwodecades,biocatalystshavecapturedanimportantplaceincontemporaryorganicsynthesis,whichisreflectedbythefactthat~8%ofallpaperso
6、nsyntheticorganicchemistrycontainedelementsofbiotransformationsasearlyasin1991withanever-increasingproportion.Itisnowgenerallyac-cepted,thatbiochemicalmethodsrepresentapowerfulsynthetictooltocom-plementothermethodologiesinmodernsyntheticorganicchemistry.Whereasseveralareasofbioc
7、atalysis–inparticulartheuseofeasy-to-usehydrolases,suchasproteases,esterasesandlipases–aresufficientlywellre-searchtobeappliedineverystandardlaboratory,othertypesofenzymesarestillwaitingtobediscoveredwithrespecttotheirapplicabilityinorganic-chemistrytransformationsonapreparative
8、scale.Thislatterpointisstressedinthisvolume,whi