Organometallic osmium arene complexes with potent cancer cell cytotoxicity.

8192 J.Med.Chem.2010,53,8192–8196 DOI: 10.1021/jm100560f Organometallic Osmium Arene Complexes with Potent Cancer Cell Cytotoxicity YingFu,†AbrahaHabtemariam,†AnaM.Pizarro,†SabineH.vanRijt,†DavidJ.Healey,‡PatriciaA.Cooper,‡ StevenD.Shnyder,‡GuyJ.Clarkson,†andPeterJ.Sadler*,† †DepartmentofChemistry,UniversityofWarwick,GibbetHillRoad,Coventry,CV47AL,U.K.,and ‡InstituteofCancerTherapeutics, UniversityofBradford,RichmondRoad,Bradford,BD71DP,U.K. ReceivedMay8,2010 Iodidoosmium(II)complexes[Os(η6-arene)(XY)I] þ (XY=p-hydroxyorp-dimethylaminophenylazopyr- idine,arene=p-cymeneorbiphenyl)arepotentlycytotoxicatnanomolarconcentrationstowardapanelof humancancercelllines;e.g.,IC =140nMfor[Os(η6-bip)(azpy-NMe )I] þ towardA2780ovariancancer 50 2 cells.Theyexhibitlowtoxicityandnegligibledeleteriouseffectsinacoloncancerxenograftmodel,giving risetothepossibilityofabroadtherapeuticwindow.Themostactivecomplexesarestableandinerttoward aquation.Theircytotoxicactivityappearstoinvolveredoxmechanisms. Introduction (phenylazopyridine-R)Z]þwherearene=p-cymene(p-cym) or biphenyl (bip), R=hydrogen (H), hydroxyl (OH), or Thesuccessofplatinumcomplexes(e.g.,cisplatinandcar- dimethylamino(NMe ),andZ=chlorideoriodide(Chart1). boplatin) asanticancerdrugsiswell-known; however,these 2 TheX-raycrystalstructuresoffivecomplexesarereportedand drugshavealimitedspectrumofactivityandcanhavesevere their chemical reactivity investigated. Surprisingly, several of toxic side effects and tumors often develop resistance.1,2 A theseOsIIphenylazopyridinecomplexesareanorderofmagni- numberofruthenium-basedcompoundshavebeenreported todisplaypromisinganticanceractivity,3-6andtwooctahe- tudemorepotentthantheclinicallyuseddrugcisplatintowarda rangeofhumancancercelllines.Anevaluationoftheirtoxicity dralruthenium(III)complexeshavereachedclinicaltrials.7,8 inmicebearingxenograftedcolontumorsisalsoreported. TheRuIIIcomplexesarethoughttobereducedtoactiveRuII speciesinvivo.Ruthenium(II)canbestabilizedbyπ-bonded ResultsandDiscussion areneligands,andarangeofRuIIarenecomplexesofthetype [Ru(η6-arene)(XY)Z)], where XY=diamine chelate and PreviouslywereportedthesynthesisoftheOsIIazopyridine Z=Cl,showinvitroandinvivoanticanceractivity.9,10These complexes [Os(η6-arene)(azpy-NMe )Cl]PF with arene = 2 6 complexes can undergo activation via hydrolysis and bind biphenyl(11)andp-cymene(12).20Cytotoxicitytestsforthese stronglytoDNA,apotentialtarget.11 complexeswerehamperedbytheirlowsolubilityandtheoccur- ArenecomplexesoftheheaviercongenerOsIIdisplaystruc- renceofprecipitationunderthetestconditionsused.Noacti- turesinthesolidstatesimilartothoseofRuIIbutaresubtly vitytowardhumanA549lungcancercellswasdetectedup differentwithregardtotheirchemicalreactivity.Forexample, to100μM.InthepresentworkwehaveexploredsimilarOsII OsIIareneethylenediaminechloridocomplexeshydrolyze∼40(cid:2) azopyridinecomplexeswithiodidereplacingchloride(Z)and more slowly and the related aqua adducts have pK a values withazpy-R(R=H,OH,andNMe 2 ).Thecomplexesremained forOs-OH 2 /OH,whichare∼1.5pK a unitslower(moreacidic) insolutionunderthecelltestingconditionswithnoapparent than those of the analogous RuII complexes.9,12 Faster ligand precipitation(videinfra). exchange in OsII complexes can be achieved by incorporating Chemistry.Sixnovelcationiciodidoosmiumarenecom- oxygen-containing chelating ligands, e.g., picolinates.13,14 Sev- plexescontainingchelatingphenylazopyridineligands(azpy, eral examples of OsII arene complexes that exhibit cancer cell azpy-OH,andazpy-NMe )weresynthesizedwherePF acts cytotoxicityhavenowbeenreported.15-19 asthecounterion.Ingene 2 ral,theyhavepooraqueous 6 solu- Theintroductionofstrongπ-acceptorchelating(XY)ligands bility (e0.2 mM), with the biphenyl complexes being less suchasbipyridineorphenylazopyridine(azpya), dramatically water-solublethanthep-cymenecomplexes.Thestructuresof changes the properties of the osmium and ruthenium com- theiodidocomplexeswithazpy(2),azpy-OH(3),andazpy- plexes.11,20,21Forexample,rutheniumcomplexesofthetype NMe (5)(Chart1)weredeterminedbyX-raycrystallography. [Ru(η6-biphenyl)(azpy)I]þ are relatively inert toward ligand Forc 2 omparison,sixchloridoanaloguesweresynthesizedand substitutionandappeartokilltumorcellsbyligand-centered thestructuresoftheazpycomplex8andazpy-NMe complex 2 redox-mediatedmechanisms.22Herewereportthesynthesis 11 were also determinedby X-raycrystallography. We have ofarangeofosmiumcomplexesofformula[Os(η6-arene)- reported the X-ray structure of 12 previously.20 We also determinedthestructureofthedimer[Os(η6-p-cym)I ] ,which 22 *Towhomcorrespondenceshould beaddressed.Phone:(þ44)024 isanimportantsyntheticintermediateinthiswork(FigureS1). 76523818.Fax:(þ44)02476523819.E-mail:P.J.Sadler@warwick.ac.uk. All of the osmium complexes adopt the familiar pseudo- aAbbreviations:NAC,N-acetyl-L-cysteine;GSH,glutathione;ROS, octahedral“piano-stool”structure(Figure1),withbondlengths reactive oxygen species; azpy, 2-(phenylazo)pyridine; azpy-OH, 4-(2- pyridylazo)phenol;azpy-NMe,4-(2-pyridylazo)-N,N-dimethylaniline. andangleswithintheexpectedranges.20Thecrystalstructureof 2 pubs.acs.org/jmc PublishedonWeb10/26/2010 r2010AmericanChemicalSociety BriefArticle JournalofMedicinalChemistry,2010,Vol.53,No.22 8193 Chart1. Osmium Phenylazopyridine Arene Complexes Stud- Interestingly,complexesbearingelectron-donatinghydroxylor iedinThisWork dimethylaminosubstituentsonthephenylringofthephenyla- zopyridineligands are an order of magnitude more active compared to complexes bearing unsubstituted azpy ligands. This may indicate that redox processes associated with the chelatedligand, e.g., involving the azo group,22 are impor- tantforactivity.Incontrast,octahedralRuIIcomplexessuch as[Ru(azpy) Cl ]containingtwounsubstitutedazpyligands 2 2 havebeenreportedtobeasactiveascisplatinagainstA2780 cells.23 Thehighpotencyoftheorganometalliciodidoosmiumcom- plexesreportedhere,withIC withinthenanomolarrange,is 50 notable. This is unprecedented for cytotoxic organometallic osmium complexes, for which activities generally fall in the micromolar range.16,18,19 In addition, their ruthenium ana- loguesweresignificantlylesscytotoxic(7tomorethan56times lessactive)intheA2780ovariancancercellline.22Inpar- ticular,theRuanalogueofcomplex3([Ru(η6-bip)(azpy-OH)I]- PF)is35timeslessactive. 6 Stability and Hydrolysis. We investigated the hydrolysis (aquation)ofthephenylazopyridinecomplexes,sincethisis apotentialmechanismforactivationofhalidoosmiumarene complexes in their interaction with possible biological tar- getssuchasDNA.16,24 Theaqueousbehaviorofthehighlyactivecomplexes[Os- (η6-p-cym)(azpy-NMe )I]PF (6,IC =0.2μM),moderately 2 6 50 activecomplex[Os(η6-p-cym)(azpy-NMe )Cl]PF (12,IC = 2 6 50 1.8 μM), and inactive complex [Os(η6-p-cym)(azpy)Cl]PF 6 (8,IC >50μM)againstA2780wasstudiedat310Kover 50 24hby1HNMR. theneutralcomplex,[Os(η6-bip)(azpy-O)I]30.5H O(3*),was The1HNMRspectraofa50μMsolutionofinactivecomplex 2 obtained by slow evaporation of a methanolic solution of 8in10mMphosphatebuffer95%D O/5%MeOD-d over24h 2 4 complex 3 ([Os(η6-bip)(azpy-OH)I]PF ). 3* has a relatively showed the disappearance of the peaks corresponding to the 6 shortO15-C12bondlength(1.258(4)A˚ )indicatingdeproton- boundazopyridineandp-cymeneligands(FigureS3),suggesting ationofthe OHgroup, withthe iodidoligandbalancing the thatthiscomplexisnotstableunderaqueousconditions.Similar chargeonOsIItoaffordaneutralcomplex.Awatermoleculein behaviorhasbeenobservedfortherutheniumanalogue[Ru(η6- thelatticeformsashortH-bondwiththephenoxidegroupand p-cym)(azpy)Cl]PF.11Incontrast,complexes6and12didnot 6 bridgestwophenoxidesofneighboringcomplexes(FigureS2). show ligand loss and neither did they hydrolyze as judged by ThepK oftheazpy-OHligandin3wasdeterminedtobe∼6.9 their1HNMRspectra,whichremainedunchanged(FigureS3). a (comparableto6.5fortherutheniumanalogue),11andsothe Inaddition,ESI-MSanalysesshowedionscorrespondingtothe complexwouldbeexpectedtobedeprotonatedunderthecondi- chloridoandiodidocomplexesonly,andUV-visspectrain tionsofthecytotoxicityassays(pH7.4),asshownintheX-ray 10%methanol/90%watershowednochangeover24h(Figure structure.Selectedbondlengthsandanglesforthesestructures S4).Anattempttoremovethechloridefromtheaqueoussolu- arelistedintheSupportingInformation(TableS1). tionof12byreactingitwithsilvernitrateunderrefluxover- Cytotoxicity.Incontrasttopreviousstudiesoncomplexes nightdidnotresultintheexpectedaquaproduct.Thechlorido 11and12,20thecomplexesweresolubleintheculturemedium complex was the only species detected by mass spectrometry attheconcentrationstestedandnoprecipitationwasobserved (FigureS6),indicatingastrongOs-Clbond. after24h.Noneoftheazopyridineligandsshowedcytotoxic Theseobservationssuggestthatactivecomplexes6and12 activity against A2780 human ovarian cancer cells up to arestableunderbiologicallyrelevanttestingconditions.In 100 μM. The IC of the osmium phenylazopyridine com- addition, the inertness of the Os-I bond suggests that 50 plexes(Chart1)rangedfrom0.14μMfortheiodidobiphenyl hydrolysis process is not critical for the activation of these complexes3and5withazpy-OHandazpy-NMe ligandsto complexesanditisconsistentwithpreviousobservationson 2 >50 μM for the chlorido complex 8 containing azpy in the theanalogousRuIIazpycomplexes,22implyingthattheazpy humanovariancelllineA2780(Table1A).Fromthesepre- ligandplaysanimportantroleintheactivity. liminaryresultsthreecomplexes(3,6,and12)wereselected EffectofN-Acetyl-L-cysteine(NAC)onCytotoxicity.Pre- forfurtherevaluationagainstacisplatin-resistantsublineof treatmentofcellswithNACcanblockcisplatin-dependent A2780,A2780/cis,aswellasagainstapanelofhumancancer caspase-3 activation and apoptosis by inhibiting the accu- celllinesofdifferinghistiotype.Complexes3and6(Table1B) mulationofintracellularreactiveoxygenspecies(ROS)and showedatleast10-foldgreaterpotencythancisplatinagainst maintaining intracellular GSH levels.25To investigatepos- allcelllinestestedapartfromRT-112(bladder),whichdemon- sibleinvolvementofROSinthecytotoxicityofazopyridine strated a 3-fold difference for complex 3. Complex 12 OsIIarenecomplexes,weinvestigatedtheeffectofpretreat- showedsimilarpotencytocisplatinoverthecelllinepanel.The mentofcellswithNAC.Cisplatinwasusedasthepositive highest activity in comparison to the reference cisplatin for control, whereas cells not treated with osmium complexes allthreecomplexeswasseenforthePC-3(prostate)cellline. servedasthenegativecontrol. 8194 JournalofMedicinalChemistry,2010,Vol.53,No.22 Fuetal. Figure1. X-raycrystalstructuresof(A)[Os(η6-p-cym)(azpy)I]þ(2),(B)[Os(η6-bip)(azpy-O)I](3*),(C)[Os(η6-bip)(azpy-NMe )I]þ(5),(D) 2 [Os(η6-p-cym)(azpy)Cl]þ(8), and (E) [Os(η6-bip)(azpy-NMe )Cl]þ (11), with thermal ellipsoids drawn at50% probability. The hydrogen 2 atoms,counterions(PF ),andsolventwatermoleculeshavebeenomittedforclarity. 6 Table1. (A)IC forComplexes1-12inHumanOvarianCellLineA2780and(B)IC for3,6and12inA2780/cisOvarian,A549Lung,HCT-116 50 50 Colon,MCF-7Breast,PC-3Prostate,andRT-112BladderHumanCancerCellLinesa (A)IC for1-12andCisplatin 50 complex IC (μM) 50 [Os(η6-bip)(azpy)I]PF 1 5.4(0.8 6 [Os(η6-p-cym)(azpy)I]PF 2 10.3(0.1 6 [Os(η6-bip)(azpy-OH)I]PF 3 0.14(0.01 6 [Os(η6-p-cym)(azpy-OH)I]PF 4 0.32(0.20 6 [Os(η6-bip)(azpy-NMe)I]PF 5 0.14(0.01 2 6 [Os(η6-p-cym)(azpy-NMe)I]PF 6 0.18(0.01 2 6 [Os(η6-bip)(azpy)Cl]PF 7 13.9(3.8 6 [Os(η6-p-cym)(azpy)Cl]PF 8 >50 6 [Os(η6-bip)(azpy-OH)Cl]PF 9 0.84(0.1 6 [Os(η6-p-cym)(azpy-OH)Cl]PF 10 1.3(0.2 6 [Os(η6-bip)(azpy-NMe)Cl]PF 11 3.9(0.3 2 6 [Os(η6-p-cym)(azpy-NMe)Cl]PF 12 1.8(0.1 2 6 cisplatin 1.8(0.1 (B)IC for3,6and12andCisplatin 50 IC (μM) 50 complex A2780/cis A549 HCT-116 MCF-7 PC-3 RT-112 3 0.19(0.04 0.42(0.07 0.34(0.02 0.31(0.02 0.37(0.08 0.42(0.06 6 0.23(0.05 0.38(0.07 0.22(0.02 0.20(0.01 0.62(0.12 0.25(0.02 12 1.77(0.68 5.23(1.10 0.93(0.05 1.12(0.81 6.80(0.00 2.17(0.55 cisplatin 4.03(2.08 4.10(2.11 2.58(0.55 3.02(1.11 21.47(4.05 1.35(0.73 aDataarethemeanofthreeexperimentsandarereportedasmean(standarderrorofthemean(SEM). A2780cells were treated withthe iodido complexes3, 5, cellgrowthto<30%ofthecontrolvalue(Figure2).Pretreat- and6andchloridocomplex12atconcentrationsthatwere mentwith5mMNACfor2handcotreatmentwithosmium 1.2-1.8(cid:2)theirrespectiveIC values,andforcisplatinacon- complexes for 24 h to increase the intracellular glutathione 50 centration2.5(cid:2)itsIC valuewasused.Thesedosesreduced concentration,22resultedintheinhibitionoftheantiproliferation 50 BriefArticle JournalofMedicinalChemistry,2010,Vol.53,No.22 8195 Figure2. CellviabilityofA2780humanovariancancercellsafter 24hexposuretoosmiumcomplexesorcisplatinfollowedby72h recovery(redbars),andcellviabilityforcellsthatwerepretreatedwith 5mMNACfor2hpriortotheadditionoftheosmiumcomplexes orcisplatin(bluebars).Dosesofcomplexeswereasfollows:[Os(η6- Figure3. Meanrelativebodyweightcurvesforcomplexes3and6 bip)(azpy-OH)I]PF (3),0.25μM;[Os(η6-bip)(azpy-NMe)I]PF (5), administeredintravenouslyasasingledoseonday0attheirmax- 6 2 6 0.25 μM; [Os(η6-p-cym)(azpy-NMe 2 )I]PF 6 (6), 0.25 μM; [Os(η6-p- imumsolubledoseof40mg3kg-1tomicebearingHCT-116human cym)(azpy-NMe)Cl]PF (12),2.5μM;CDDP(cisplatin),5μM.The tumorxenografts(n=2).Fluctuationsinbodyweightarewellwithin 2 6 errorbarsarestandarddeviationsofsixreplicates.C=control. thenormallimits,suggestingthatneithercomplexistoxic. thatwiththecomparativelackoftoxicityofthecomplexesthere effectsofiodidocomplexes3,5,and6.Thiswasshownbytheir islikelytobeamuchbroadertherapeuticwindow.Thiswillbe growth levels of >70% when pretreated with NAC. For investigated further in extensive in vivo pharmacokinetic and chloridocomplex12,theNACpretreatmentandcotreatment efficacystudies. hadonlyasmalleffectonrestoringgrowth(Figure2).These results suggest that, unlike the azopyridine osmium arene Conclusion iodidocomplexesorcisplatin,thecytotoxicityassociatedwith Pseudo-octahedral “piano-stool” organometallic osmium osmiumchloridocomplex12doesnotappeartodependonthe arenecomplexeshavepotentialforexplorationasanticancer production of reactive oxygen species (ROS) but may be complexes. They are attractive, since they provide a hydro- explainedbyadifferentmechanismofcytotoxicactivity. phobicarenefaceamenabletoawidevarietyofsubstitutions To investigate the possibility that the complexes might togetherwiththreeothervariablecoordinationpositions.The reactdirectlywithNACandthattheeffectsarenotmerely areneandtheotherligandscanhaveamajoreffectondeter- due to thiol levels in cells, a solution containing 1.0 mM miningtheelectrondistributionwithinthecomplex,control- [Os(η6-p-cym)(azpy-NMe )I]PF (6) and excess (7.35 mM) 2 6 lingtheirratesofligandsubstitutionandtheirredoxproperties NACin30%acetone-d and70%phosphatebuffer(10mM, 6 (metal- or ligand-centered). In the present case the chelated pH7.0)wasmonitoredby1HNMRspectroscopyfor24hat azopyridineligandisaσ-donorandastrongπ-acceptor;i.e., 310 K. No new peaks appeared in the 1H NMR spectrum thereisastrongback-donationofelectronsfromOsIIontothe (Figure S5), suggesting that complex 6 and probably the azopyridineligand,producingalargeeffectonoverallreactiv- otheriodidocomplexesdonotreadilyreactwithNAC. ity.Iodidocomplexesweremorecytotoxicthantheanalogous ReactionswithGlutathione(GSH). Since some phenyla- chloridocomplexes.Inaddition,iodidocomplexescontaining zopyridine ruthenium arene complexes appear to oxidize p-hydroxyl orp-dimethylaminosubstituentsonthephenyla- GSHcatalyticallytoformGSSG,22similarreactionswere zopyridine chelating ligand (e.g., complexes 3 and 6) were studiedfortheosmiumanalogues.The1HNMRspectrum cytotoxicatnanomolarconcentrationstowardovarian,lung, ofasolutioncontainingthehighlycytotoxiciodidocom- breast,colon,prostate,andbladderhumancancercells,anorder plex [Os(η6-p-cym)(azpy-NMe )I]PF (6) (100 μM) and a 2 6 of magnitude more potent than cisplatin and (unexpectedly) 100(cid:2)molarexcessofGSH(10mM,tomimicintracellular thantheirRuIIanalogues.Theseiodidocomplexesarealsoinert conditions)showed little change over 24 h. This suggests towardhydrolysis.Interestingly,theircytotoxicitywasinhibited thatcomplex6doesnotcatalyticallyoxidizeGSH,unlike theanalogousRuIIcomplex.Themechanismofcytotoxic bypretreatmentofthecellswthN-acetyl-L-cysteine,suggesting thatreactiveoxygenspecies(ROS)areinvolvedintheirmecha- activity for these OsII azopyridine complexes therefore nismofaction,althoughunliketheirRuIIareneazopyridine appearstobedifferentfromthatoftheRuIIanaloguesand analogues,theOsIIcomplexesinvestigatedheredonotoxidize alsodifferentfromthosebearinghydrolyzableRu/Os-Cl GSHcatalytically.Moreencouragingly,theseOsIIcomplexes bonds. exhibited low toxicity and negligible deleterious effects in a Evaluation of in Vivo Toxicity. Complexes 3 and 6 were HCT-116 tumor xenograft model, indicating that they may selectedforfurtherinvivoevaluationbasedontheirpromis- exhibitabroadtherapeuticwindow. inginvitroactivity.Onevaluationoftheirtoxicityinanude mouse tumor HCT-116 xenograft model, the complexes demonstrated negligible deleterious effects at doses up to and ExperimentalSection includingtheirmaximumsolubledoseof40mg3kg -1(Figure3). General Information. Details of chemicals and equipment, Thisdoseisapproximately6timeshigherthanthemaximum X-raycrystallography,pH*measurements,cellcultures,N-acetyl- tolerateddoseofcisplatininthesametumormodel,andsuggests L-cysteine (NAC) treatment of cell, determination of IC 50 8196 JournalofMedicinalChemistry,2010,Vol.53,No.22 Fuetal. values,andevaluationofinvivotoxicityareintheSupport- (8) Rademaker-Lakhai,J.M.;vandenBongard,D.;Pluim,D.;Beijnen, ingInformation. J.H.;Schellens,J.H.AphaseIandpharmacologicalstudywith Synthesis.Complexes1-12werepreparedbythesamegeneral imidazolium-trans-DMSO-imidazole-tetrachlororuthenate,anovel rutheniumanticanceragent.Clin.CancerRes.2004,10,3717–3727. method:reactionoftheappropriatephenylazopyridinederivative (9) Wang,F.;Habtemariam,A.;vanderGeer,E.P.;Fernandez,R.; withthedimers[Os(η6-bip)Cl ] ,[Os(η6-bip)I ] ,[Os(η6-p-cym)- 22 22 Melchart,M.;Deeth,R.J.;Aird,R.;Guichard,S.;Fabbiani,F.P.; Cl 2 ] 2 ,or[Os(η6-p-cym)I 2 ] 2 .Thisisillustratedbelowforcomplex Lozano-Casal,P.;Oswald,I.D.;Jodrell,D.I.;Parsons,S.;Sadler, 6.Thepuritiesofallcompoundspreparedweredeterminedtobe P.J.Controllingligandsubstitutionreactionsoforganometallic g95%byelementalanalysis.ThedetailsareintheSupporting complexes:tuningcancercellcytotoxicity.Proc.Natl.Acad.Sci. Information. U.S.A.2005,102,18269–18274. [Os(η6-p-cym)(azpy-NMe)I]PF (6). [Os(η6-p-cym)I] (100.0 (10) Aird,R.E.;Cummings,J.;Ritchie,A.A.;Muir,M.;Morris,R.E.; 2 6 22 Chen,H.;Sadler,P.J.;Jodrell,D.I.Invitroandinvivoactivityand mg, 0.086 mmol) was dissolved in methanol (50 mL) at 313 K. crossresistanceprofilesofnovelruthenium(II)organometallicarene Azpy-NMe 2 (39.5mg,0.175mmol)inmethanol(10mL)wasadded complexesinhumanovariancancer.Br.J.Cancer2002,86,1652–1657. dropwise;thesolutioncolorchangedfromorangetoblueimmedi- (11) Dougan, S. J.; Melchart, M.; Habtemariam, A.; Parsons, S.; ately.Thesolutionwasstirredatambienttemperaturefor3h.The Sadler,P.J.Phenylazo-pyridineandphenylazo-pyrazolechlorido ruthenium(II)arenecomplexes:areneloss,aquation,andcancer volumewasreducedtoabout10mLbyremovalofmethanolona cellcytotoxicity.Inorg.Chem.2006,45,10882–10894. rotary evaporator, and ammonium hexafluorophosphate (141.8 (12) Peacock,A.F.A.;Habtemariam,A.;Fernandez,R.;Walland,V.; mg.0.87mmol)wasadded.Thesolutionwasthenleftinthefreezer Fabbiani,F.P.A.;Parsons,S.;Aird,R.E.;Jodrell,D.I.;Sadler, for24h.Darkcoloredpowderprecipitatedwhichwascollected P.J.Tuningthereactivityofosmium(II)andruthenium(II)arene by filtration, washed with cold ethanol and diethyl ether, then complexesunderphysiologicalconditions.J.Am.Chem.Soc.2006, finallydriedinvacuum.Yield:122.7mg(87%).ESI-MScalcdfor 128,1739–1748. C H IN Os,m/z679.1;found,679.0.1HNMR((CD ) CO):δ (13) Peacock,A.F.A.;Sadler,P.J.Medicinalorganometallicchem- 23 28 4 32 istry: designing metal arene complexes as anticancer agents. 9.43(d,1H,J=6Hz),8.65(d,1H,J=8Hz),8.29-8.22(m,3H), Chem.-AsianJ.2008,3,1890–1899. 7.64(m,1H),6.97(d,2H,J=9Hz),6.59(d,1H,J=6Hz),6.30 (14) vanRijt,S.H.;Peacock,A.F.A.;Johnstone,R.D.L.;Parsons,S.; (m,3H),3.41(s,3H),2.80(s,6H),2.61(m,1H),1.02(d,3H,J=6 Sadler,P.J.Organometallicosmium(II)areneanticancercomplexes Hz),0.98(d,3H,J=6Hz)CHNanalysis.Found:C,33.42%;H, containingpicolinatederivatives.Inorg.Chem.2009,48,1753–1762. 3.28%; N, 6.72%. Calcd for C H FIN OsP: C, 33.58% H, (15) Dorcier,A.;Ang,W.H.;Bolano,S.;Gonsalvi,L.;Juillerat-Jeannerat, 23 28 6 4 L.;Laurenczy,G.;Peruzzini,M.;Phillips,A.D.;Zanobini,F.;Dyson, 3.43%N,6.81%. P.J.InvitroevaluationofrhodiumandosmiumRAPTAanalogues: X-rayCrystallography.X-raycrystallographicdataforcom- thecasefororganometallicanticancerdrugsnotbasedonruthenium. pounds2,3*,5,8,11,and14havebeendepositedintheCam- Organometallics2006,25,4090–4096. bridge Crystallographic Data Centre with CCDC references (16) Peacock,A.F.A.;Parsons,S.;Sadler,P.J.Tuningthehydrolytic numbers776271,776270,776273,776268,776269,and776272, aqueouschemistryofosmiumarenecomplexeswithN,O-chelating ligandstoachievecancercellcytotoxicity.J.Am.Chem.Soc.2007, respectively. 129,3348–3357. (17) Schmid,W.F.;John,R.O.;Arion,V.B.;Jakupec,M.A.;Keppler, Acknowledgment. WethankDr.MichaelKhan(Biological B.K.Highlyantiproliferativeruthenium(II)andosmium(II)arene Sciences,UniversityofWarwick)forprovisionoffacilitiesfor complexes with paullone-derived ligands. Organometallics 2007, 26,6643–6652. cell culture, and we thank the MRC, EPSRC (Knowledge (18) vanRijt,S.H.;Hebden,A.J.;Amaresekera,T.;Deeth,R.J.;Clarkson, Transfer Network), and Science City/EU ERDF/AWM for G.J.;Parsons,S.;McGowan,P.C.;Sadler,P.J.Amidelinkage funding. isomerismasanactivityswitchfororganometallicosmiumand rutheniumanticancercomplexes.J.Med.Chem.2009,52,7753–7764. (19) vanRijt,S.H.;Mukherjee,A.;Pizarro,A.M.;Sadler,P.J.Cyto- Supporting Information Available: Details of procedures toxicity,hydrophobicity,uptake,anddistributionofosmium(II) and experimental data for all synthesized compounds, instru- anticancercomplexesinovariancancercells.J.Med.Chem.2010, mentation and methods, Table S1, and Figures S1-S6. This 53,840–849. material is available free of charge via the Internet at http:// (20) Peacock,A.F.A.;Habtemariam,A.;Moggach,S.A.;Prescimone, A.; Parsons, S.; Sadler, P. J. Chloro half-sandwich osmium- pubs.acs.org. 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