DrAmitBasak-DepartmentofChemistry：Amit巴萨克-化学系博士

《DrAmitBasak-DepartmentofChemistry：Amit巴萨克-化学系博士》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、Lecture2Importanceofchirality:Manydrugmoleculesarechiral.Howevertheyaresoldasracemates.Inmostcasesonlyoneenantiomeristheactiveagent.Theotherenantiomerisusuallyinactivewhileinsomecasestheymaybetoxic.Example:antiinflammatoryagentRisomerinactiveSisomerisactiveSisomerisact

2、iveRisomerinactive(nonantiinflammatory)aswellasnephrotoxicMethyldopa(antihypertensive)(S–isomerisactive)ThesedrugsarewhatarecalledsyntheticdrugsIfthedrugisanaturalproduct,itisavailableinchiralform.ChiralDrugsDrugsneedtobesoldintheformwhichispharmacologicallyactive.Thal

3、idomideTwoforms:(+)&(-)OrR/SOneformusedasadrugOtherformisateratogenItwassoldintheracemicform.Teratogenmoleculescausebirthdefect.Thedrugwaswithdrawn.ImportanceofchiralitywasdemonstratedthroughthispainfulexperienceQ.Whichmoleculeischiral?Ans.Moleculehavinganonsuperimposa

4、blemirrorimage.Q.HowdoIknowwhetherornotamoleculehasanonsuperimposablemirrorimage?Ans.Onecancheckthesymmetryelementsofthemoleculeandthencomeoutwithaconclusion.Q.WhatareSYMMETRYELEMENTS?Ans.Theseareelementsthatmaybepresentinamoleculeandgiveanideahowsymmetricalamoleculeis

5、.Q.Howmanysymmetryelementsamoleculecanpossess?Ans.Foura)simpleaxis[Cn]b)plane[σ].c)centre[I]d)alternatingaxis[Sn].SimpleaxisofSymmetry(Cn):Amoleculehasanfoldsimpleaxisofsymmetryifitisrotatedbyanangleof3600/naroundtheaxis,youobtainasamelookingmolecule.Planeofsymmetry(σ)

6、:Animaginarymirrorplanedividingthemoleculeintotwohalvessuchthatonehalfisthemirrorimageoftheotherhalf.Centreofsymmetry(i):Animaginarypoint….ifanysubstituentisjoinedbyalineandifthelineisextendedinoppositedirection,youobtainthesamesubstituentatequaldistance.Thisistruefore

7、verysubstituentpresentinthemolecule.Alternatingaxisofsymmetry(Sn)Amoleculerotatedaroundanaxisby3600/nanimagetakenthroughamirrorplacedperpendiculartotheaxisthemirrorimagelooksidenticalwiththeoriginal.Whenamoleculeisdevoidofallthesymmetryelements,itiscalled“asymmetric”.W

8、henamoleculeisdevoidof,IandSn,itiscalled“dissymmetric”IfamoleculeisdevoidofSn,itisdissymmetricandhence“chiral”Dissym