制药工程专业英语第151316.docx

制药工程专业英语第151316.docx

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制药工程专业英语第151316

Unit1ProductionofDrugs

Dependingontheirproductionororiginpharmaceuticalagentscanbesplitintothreegroups:

I.Totallysyntheticmaterials（synthetics），

Ⅱ.Naturalproducts，and

Ⅲ.Productsfrompartialsyntheses（semi-syntheticproducts）.

TheemphasisofthepresentbookisonthemostimportantcompoundsofgroupsIandⅢ一thusDrugsynthesis.Thisdoesnotmean，however，thatnaturalproductsorotheragentsarelessimportant.Theycanserveasvaluableleadstructures，andtheyarefrequentlyneededasstartingmaterialsorasintermediatesforimportantsyntheticproducts.

Table1givesanoverviewofthedifferentmethodsforobtainingpharmaceuticalagents.

Table1Possibilitiesforthepreparationofdrugs

MethodsExamples

1.Totalsynthesis-over75%ofallpharmaceuticalagents（synthetics）

2.Isolationfromnaturalsources（naturalproducts）:

2.1Plants-alkaloids;enzymes;heartglycosides;polysaccharides;tocopherol;

steroidprecursors（diosgenin,sitosterin）;citral（intermediateproductfor

vitaminsA,E，andK）

2.2Animalorgans一enzymes;peptidehormones;cholicacidfromgall;insulin）fromthe

pancreas;seraandvaccines

2.3Othersources一cholesterolfromwooloils;L-aminoacidsfromkeratinandgelatine

hydrolysates

3.Fermentation一antibiotics;L-aminoacids;dextran;targetedmodificationsonsteroids，

e.g.11-hydroxylation;alsoinsulin,interferon,antibodies,peptide

hormones，enzymes，vaccines

4.Partialsyntheticmodificationofnaturalproducts（semisyntheticagents）:

一alkaloidcompounds;semisynthetic/3-lactamantibiotics;steroids;humaninsulin

Severaltherapeuticallysignificantnaturalproductswhichwereoriginallyobtainedfromnaturalsourcesaretodaymoreeffectively-i.e.moreeconomically-prepared..bytotalsynthesis.SuchexamplesincludeL-aminoacids，Chloramphenicol，Caffeine,Dopamine，Epinephrine，Levodopa,peptidehormones，Prostaglandins，D-Penicillamine，Vincamine，andpracticallyallvitamins.

Overthelastfewyearsfermentation-i.e.microbiologicalprocesseshasbecomeextremelyimportant.Throughmoderntechnologyandresultsfromgeneticselectionleadingtothecreationofhighperformancemutantsofmicroorganisms，fermentationhasalreadybecomethemethodofchoiceforawiderangeofsubstances.BothEukaryonts（yeastsandmoulds）andProkaryonts（singlebacterialcells，andactinomycetes）areusedmicroorganisms.Thefollowingproducttypescanbeobtained:

1.cellmaterial（singlecellprotein），

2.enzymes，

3.primarydegradationproducts（primarymetabolites），

4.secondarydegradationproducts（secondarymetabolites）.

Disregardingtheproductionofdextranfromthemucousmembranesofcertainmicroorganisms，e.g.Leuconostocmesenteroides，classes2and3aretherelevantonesforthepreparationofdrugs.Dextranitself，withamolecularweightof50,000~100,000，isusedasabloodplasmasubstitute.AmongtheprimarymetabolitestheL-aminoacidsfrommutantsofCorynebacteriumglutamicumandBrevibacteriumflavumareespeciallyinteresting.Fromtheseorganismssome350，000tonesofmonosodiumL-glutamate（foodadditive）andsome70，000tonesofL-lysine（supplementforvegetableproteins）areproduced.Furtherimportantprimarymetabolitesarethepurinanucleotides，organicacids，lacticacid，citricacid，andvitamins，forexamplevitaminB,2fromPropionibacteriumshermanii.

Amongthesecondarymetabolitestheantibioticsmustbementionedfirst.ThefollowingfivegroupsrepresentayearlyworldwidevalueofUS-$17billion:

penicillins（Penicilliumchrysogenum），

cephalosporins（Cephalosporiumacremonium），

tetracyclines（Streptomycesaureofaciens），

erythromycins（Streptomyceserythreus），

aminoglycosides（e.g.streptomycinfromStreptomycesgriseus）.

About5000antibioticshavealreadybeenisolatedfrommicroorganisms，butoftheseonlysomewhatfewerthan100areintherapeuticuse.Itmustberemembered，however，thatmanyderivativeshavebeenmodifiedbypartialsynthesisfortherapeuticuse;some50，000agentshavebeensemisyntheticallyobtainedfrom户lactamsaloneinthelastdecade.Fermentationsarecarriedoutinstainlesssteelfermentorswithvolumesupto400m3.Toavoidcontaminationofthemicroorganismswithphagesetc.thewholeprocesshastobeperformedundersterileconditions.Sincethemoreimportantfermentationsoccurexclusivelyunderaerobicconditionsagoodsupplyofoxygenorair（sterile）isneeded.Carbondioxidesourcesincludecarbohydrates，e.g.molasses，saccharides，andglucose.Additionallythemicroorganismsmustbesuppliedinthegrowthmediumwithnitrogen-containingcompoundssuchasammoniumsulfate，ammonia，orurea，aswellaswithinorganicphosphates.Furthermore，constantoptimalpHandtemperaturearerequired.InthecaseofpenicillinG，thefermentationisfinishedafter200hours，andthecellmassisseparatedbyfiltration.Thedesiredactiveagentsareisolatedfromthefiltratebyabsorptionorextractionprocesses.Thecellmass，ifnotthedesiredproduct，canbefurtherusedasananimalfeedstuffowingtoitshighproteincontent.

Bymodernrecombinanttechniquesmicroorganismshavebeenobtainedwhichalsoallowproductionofpeptideswhichwerenotencodedintheoriginalgenes.ModifiedE.colibacteriamakeitthuspossibletoproduceA-andB-chainsofhumaninsulinorproinsulinanalogs.Thedisulfidebridgesareformedselectivelyafterisolation，andthefinalpurificationiseffectedbychromatographicprocedures.Inthiswayhumaninsulinisobtainedtotallyindependentlyfromanypancreaticmaterialtakenfromanimals.

Otherimportantpeptides，hormones，andenzymes，suchashumangrowthhormone（HGH），neuroactivepeptides，somatostatin，interferons，tissueplasminogenactivator（TPA），lymphokines，calciumregulatorslikecalmodulin，proteinvaccines，aswellasmonoclonalantibodiesusedasdiagnostics，aresynthesizedinthisway.

Theenzymesorenzymaticsystemswhicharepresentinasinglemicroorganismcanbeusedfordirectedstereospecificandregiospecificchemicalreactions.Thisprincipleisespeciallyusefulinsteroidchemistry.Herewemayreferonlytothemicrobiological11-a-hydroxylationofprogesteroneto11-a-hydroxyprogesterone，akeyproductusedinthesynthesisofcortisone.Isolatedenzymesareimportanttodaynotonlybecauseofthetechnicalimportanceoftheenzymaticsaccharificationofstarch，andtheisomerizationofglucosetofructose，Theyarealsosignificantinthecountlesstestproceduresusedindiagnosingillness，andinenzymaticanalysiswhichisusedinthemonitoringoftherapy.

Anumberofenzymesarethemselvesusedasactiveingredients.Thuspreparationscontainingproteases（e.g.chymotrypsin，pepsin，andtrypsin），amylasesandlipases，mostlyincombinationwithsyntheticantacids，promotedigestion.Streptokinaseandurokinaseareimportantinthrombolytics，andasparaginaseisusedasacytostaticagentinthetreatmentofleukemia.

Finallymentionmustbemadeoftheimportantuseofenzymesas`biocatalysts’inchemicalreactionswheretheirstereospecificityandselectivitycanbeused.KnownexamplesaretheenzymaticcleavageofracematesofN-acetyl-D，L-aminoacidstogiveL-aminoacids，theproductionof8-aminopenicillanicacidfrombenzylpenicillinbymeansofpenicillinamidaseandtheaspartase-catalysedstereospecificadditionofammoniatofumaricacidinordertoproduceL-asparticacid.

Intheseapplicationstheenzymescanbeusedinimmobilizedforms-somehowboundtocarriers-andsousedasheterogeneouscatalysts.Thisisadvantageousbecausetheycantheneasilybeseparatedfromthereactionmediumandrecycledforfurtheruse.

Anotherimportantprocessdependingonthespecificactionofproteasesisappliedfortheproductionofsemisynthetichumaninsulin.Thisstartswithpiginsulininwhichthealanineinthe30-positionoftheB-chainisreplacedbyathreoninetert-butylesterbytheselectiveactionoftrypsin.Theinsulinesterisseparated，hydrolyzedtohumaninsulinandfinallypurifiedbychromatographicprocedures.

Sourcesforenzymesincludenotonlymicroorganismsbutalsovegetableandanimalmaterials.

InTable1itwasalreadyshownthatover75%ofallpharmaceuticalagentsareobtainedbytotalsynthesis.Thereforeknowledgeofthesyntheticroutesisuseful.Understandingalsomakesitpossibletorecognizecontamination.oftheagentsbyintermediatesandby-products.Forthereasonofeffectivequalitycontroltheregistrationauthoritiesinmanycountriesdemandasessentialsforregistrationathoroughdocumentationontheproductionprocess.KnowledgeofdrugsynthesesprovidestheR&Dchemistwithvaluablestimulationaswell.

Thereareneitherpreferredstructuralclassesforallpharmaceuticallyactivecompoundsnorpreferredreactiontypes.Thisimpliesthatpracticallythewholefieldoforganicandinpartalsoorganometallicchemistryiscovered.Nevertheless，alargernumberofstartingmaterialsandintermediatesaremorefrequentlyused，andsoitisusefultoknowthepossibilitiesfortheirpreparationfromprimarychemicals.Forthisreasonitisappropriatesomewhereinthisbooktoillustrateatreeofespeciallyimportantintermediates.Theselatterintermediatesarethekeycompoundsusedinsyntheticprocessesleadingtoanenormousnumberofagents.Forthemostpartchemicalsareinvolvedwhichareproducedinlargeamounts.Inasimilarwaythisisalsotruefortheintermediatesbasedontheindustrialaromaticcompoundstoluene，phenolandchlorobenzene.Furtherkeycompoundsmaybeshowninatablewhichcanbeusefulintracingcross-relationshipsinsyntheses.f

Inadditiontotheactualstartingmaterialsandintermediatessolventsarerequiredbothasareactionmediumand,for