Abstract
An oxidative ring opening reaction of the central ring C in the alkaloid Luotonin A and two of its derivatives was found to occur upon heating with an excess amine and potassium carbonate in dimethylsulfoxide (DMSO) solution in the presence of air oxygen. The structure of the novel amide-type products was elucidated and a possible mechanism for this reaction is proposed. Four of the new compounds show moderate in vitro anticancer activity towards human colon adenocarcinoma cells.
Highlights
In sseeaarrcchh ooffnnewewanatnictiacnacnecreragaegnetsn,ts,trustcrtuucrtaulrmalomdiofidcaifiticoantsioonfs thoef athlkealaolikdalLouidotoLnuiontoAni(nfirAst97ha[v1e])fohuavned fcoounnsiddecroanbsliedienrtaebrleestindtueriensgt dthueripnagstthtwe opadsetcatwdeos d[2e–c1a2d]e.sL[i2k–e1i2t]s
Based on the combined spectroscopic evidence, it can be concluded that (a) the expected nucleophilic substitution of the fluorine atom with pyrrolidine has taken place and (b) the C-ring of the pentacyclic scaffold has undergone an oxidative ring opening, involving another pyrrolidine unit that is attached to the quinoline core via an amide function
As neither the amine component, nor the inorganic base, nor the solvent have oxidative properties to perform the observed oxidation of the benzylic CH2 group of ring C into an amide function, we suspected atmospheric oxygen to play a crucial role in this process
Summary
In sseeaarrcchh ooffnnewewanatnictiacnacnecreragaegnetsn,ts,trustcrtuucrtaulrmalomdiofidcaifiticoantsioonfs thoef athlkealaolikdalLouidotoLnuiontoAni(nfirAst (ifisorlsatteisdoliante1d99i7n[19])97ha[v1e])fohuavned fcoounnsiddecroanbsliedienrtaebrleestindtueriensgt dthueripnagstthtwe opadsetcatwdeos d[2e–c1a2d]e.sL[i2k–e1i2t]s. A number of new nLuumotboenrinoAf ndeewrivaLtuivoetsoncoinulAd bdeemriavdaetivaevsailcaobuleldvibaethmesaedtewaovraoiulatbesledivrieacttlhy,easdedtiwtioonraol umteosdidfiicraetciotlnys, abdydrietipolnaacel mmeondtifoicfaetxioisntsinbgysruebpslaticteumenetnst wofeerexiesntivnigsasguebdstiintuoenrdtserwteorefuernthviesraegxetdenindoorudrercotomfpuortuhnedr elixbtreanrdy.oIunrpcaormticpuoluarn,dnulicblreaorpyh. iIlnicpsaurbtisctuitluatri,onnuocfleaoflpuhiolrico sfuubnscttiitountiaolintyofwaitfhluaomroinfeusnacptipoenaarleitdy qwuiitthe apmroimneissianpgpienavreiedwquofittehperroempoisritnegd ifnacvilieewtraonfstfhoermreaptoiortnedoff8a-cflilueotrraonqsufionromlianteisoninotof 8t-hfelucoorrorqesupinoonldininegs i8n-t(odit)haelkcyolarrmesinpooqnudiinnogli8n-e(dsiv)aialknyulacmleionpohqiuliicnsoulibnsetsituvitaionnu[c2l2e,o2p3]h.ilHicesreuibns,twituetrioenpo[r2t2o,2n3]t.hHe esyrenitnh,ewsies roefpaorhtitohnertthoeusnyknnthoewsnis 4o-ffluaohriothdeerrtoivautnivkenoowf Lnu4o-tfolunoinroAde(croivnattaiivneinogf tLhueo8to-flnuinorAoq(ucoinnotlaiinneinmgotthife) 8a-nfdluothroeqoubisneorlvinaetiomnootiff)aannudntphreecoebdseenrvteadtioonxiodfaatinveunoppreenciendgeonfterdinogxiCdaotnivaettoepmenpitnegd onfurcilnegopChiolinc asuttbemstiptutetdionnureclaecotipohnisliwc siuthbsptriitmutaioryn orerascetcioonnds awryithampriinmesa.ry or secondary amines
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