2429
Inorg. Chem. 1992, 31, 2429-2434
Contribution from the Fachbereich Chemie, Universitit Dortmund, 4600 Dortmund, Germany
Platinum(I1) Coordination to N1 and N7,Nl of Guanine: cis-DDPModel Cross-Links in the Interior and Simultaneous Cross-Links at the Periphery and the Interior of DNA Gudrun Frommer, Ilpo Mutikainen,' Ferdinand J. Pesch, Edda C.Hillgeris, Hans Preut, and Bernhard Lippert* Received October 11, 1991 The preparation and characterization of a series of mono-, di-, and trinuclear Pt(I1) complexes of 9-methylguanine (9-MeGH) are reported. The compounds contain the guanine heterocycle monoplatinated at N1 and/or diplatinated at N1 and N7. The route to these compounds involves a primary fixation of a (dien)Pt(II) entity to the N7 position, fixation of a second Pt(I1) at N1, and subsequent removal of the N7-bound Pt(I1) by cyanide. The crystal structure via X-ray diffraction of a representative tetragonal system, space group I41/a, a = 16.003 (2) A, c = 32.247 (6) example, ( ~ I I ) P ~ ( ~ - M ~ G - N ' )(4a) ~ . ~isHreported: ~O A, v = 8258 (2) A), z = 16.
The preferred cross-links of the antitumor agent cis-dia"inedichloroplatinum(II), cis-DDP, with DNA involve binding to the N7 sites of the purine bases guanine (G) and adenine (A), specifically intrastrand adducts of types GG, AG, and GXG.* These cross-linksaccount for more than 90%of all cis-DDP-bound DNA. Among the minor cross-links (=l%), two are presently known: the GG interstrand adduct and Gprotein adducts. Little is known about their possible biological significance and about the nature of any other minor ~ross-links.~ Considering the various unusual DNA secondary structures that are emerging4and their suspected role in gene regulation, cis-DPP binding patterns other than those at the purine N7 positions can be envisaged and therefore should be considered. In fact, there are several reports, e.g., on low cis-DDP affinity for oligoG sequences? on the effect of a second DNA binder on the platination att tern,^ or on a sequence dependency of a AG platination reaction,6 which somewhat modify the picture of preferential reaction with purine N7 sites. Although not directly related to the topic discussed here, a recent finding on the switch of tram-DPP from GCG to CGCG in a dodecamer oligonucleotide7 may very well be relevant to cis-DDP interactions with DNA as well. At least with tRNA, cis-DDP binding to a G and a C has been reported? and substantial binding of t r a m - D D P to cytosines both in single- and double-stranded DNA appears to be established now.9 In our laboratory, we have prepared and studied a great number of model cross-links of cis- and rram-DDP with isolated nucleobases.1° In continuation of this work and specifically of a previous paper on two Pt(I1) complexes containing N7,Nlbridging 9-methylguaninato ligands,ll we herewith report on a
series of compounds containing 9-methylguanineligands platinated exclusively at N1 or simultaneously at N1 and N7. Some of the compounds prepared represent DNA cross-linking models with concurrent cis-DDP binding at the periphery and in the interior, both in inter- and intrastrand fashion. Experimental Section
Starting Materials. C ~ ~ - ( N H ~ ) ~ CP ~~ SC- I[ ~N,(~C~H ~ ) ~ H ] ~ P ~ C ~ ~ , ~ (ex~)PtCl,,~~ [(dien)PtI]I,16 C ~ S - ( N H ~ ) ~ P ~ ( ~ - M ~cisU)C~.H~O,~
[(NH,)zPt(l-MeC)CI]Cl,18 [(dien)Pt(9-MeGH-A")](C104)2,11 ([(dien)Pt] 2(9-MeGH-N7,N1))(C104)3.2H20 (l ) , I 1 cis- [(NH,),Pt( 1MeU)(9-MeGH-N1,N?)Pt(dien)](C104)2.2.5H20 (2),11 l-methylcytosine,lgand l-methyluracilZ0were prepared as described. 9-MeGH was purchased from Chemogen (Konstanz, Germany). C~~-([N(CH,)~H]~P~(~-M~GH-N?)CI)CIO~ was prepared from cis-[N(CHp)zH]2PtC12(1 mmol), NaCl (2 mmol), and 9-MeGH (1 mmol) in HzO (200 mL). After 3 d at 40 OC, the clear solution was concentrated to a 4-mL volume, filtered from the Pt starting compound, and passed over a cation-exchange column (CM Sepharose Fast Flow; NaCl gradient). To the fraction containing the desired compound was added NaCIO, (1 mmol). Upon crystallization,the compound was obtained as pale yellow cubes in 41% yield. Anal. Calcd (found) for CIOHZoN705C12Pt: C, 20.5 (20.6); H,3.6 (3.6); N, 16.8 (16.9). Preparation of Compounds. c~s-(NH,)~P~(~-M~U)(~-M~G-"). 4.5H20 (h) was obtained in 55% yield by reaction of 2 (0.2 mmol) with NaCN (1.6 mmol) in water (20 mL) for 2 h at 20 OC, concentration to a 6-mL volume and crystallization at 4 "C. Anal. Calcd (found) for CllH26N907.5Pt: C, 22.0 (22.1); H, 4.4 (4.5); N 21.0 (21.0). cis- [(NH3)2Pt( 1-MeU)(9-MeGH-M)] C1O4.3.5H20(2g) was isolated in 28% yield as colorless crystals on slow-evaporation of a solution of 2a (0.037 "01) in HzO (2 mL), which had been brought to pH 3 by means of 0.1 N HCIOd. Anal. Calcd (found) for CIIH,,NoOln~CIPt: C, 19.7 .. -_ (19.3); H, 3.8 (3.6); N, 18.8 (i8.9). c i s , c i ~ - [ ( N H ~1-MeU)Pt(9-MeG-N1,A")Pt( )~( l-MeC)(NH3)2](ClOL),.5H,0 (2e)and cis,cis-KNHd,( l-MeU)Pt(9-MeG-N1,N?)Pt(9MeGH~N?)~N(CH,)zH],)(C10~)2~H~0 (21)were prepared as follows. ~is-[(NH,)~Pt(l-MeC)cl]Cl (0.04 mmol) and AgC104 (0.078 mmol) (0.04 "01) and analogously C~~-([N(CH~)~H]~P~(~-M~GH-N?)CI}CIO~ and AgCIO4 (0.039 mmol) were stirred in H 2 0 (10 mL) for 3 d at 20 OC. After filtration of AgCl, 2a (0.035 mmol) was added to the respective solutions and the reaction mixture was allowed to slowly evap orate. Colorless crystals of 2e (57% yield) and of 2f (51% yield) were obtained in this manner. Anal. Calcd (found) for C16H40N14017C12Pt2 ~
(1) Permanent address; Department of Chemistry, University of Helsinki,
Finnland. (2) Reviews: (a) Reedijk, J.; Fichtinger-Schepman, A. M. J.; van Oosterom, A. T.; van de Putte, P. Srrucr. Bonding 1987, 67, 53. (b) Eastman, A. Pharmacol. Ther. 1987,459,155. (c) Sherman, S.E.; Lippard, S . J. Chem. Reu. 1987,87, 1153. (3) (a) Eastman, A. Biochemistry 1985, 24, 5027. (b) Roberts, J. J.; Friedlos, F. Biochim. Biophys. Acta 1981,655,146. (4) See,e.&, various articles in: Unusual DNA Structures; Wells, R. D., Harvey, S. C., Eds.; Springer: New York, 1988. ( 5 ) Caradonna, J. P.; Lippard, S . J. In Platinum Coordination Complexes in Cancer Chemotherapy, Hacker, M. P., Douple, E. B., Krakhoff, I. H., Eds.; Nijhoff: Boston, MA, 1984; p 14. (6) Rahmouni. A.: Schwartz. A,: Leng. M. In Platinum and Other Metal Coordination Compounds in Cancer Chemotherapy;Nicolini, M., Ed.; Nijhoff: Boston, MA, 1988; p 127. (7) Comes, K. M.; Costello, C. E.; Lippard, S . J. Biochemistry 1990,29, .
I
2102.
(8) D&an, J. C. J. Am. Chem. Soc. 1984,106,7239. (9) Eastman. A.; Jennerwein, M. M.; Nagel, D. L. Chem.-Biol. Interact. 1988,67,71. (10) Lippert, B. Prog. Inorg. Chem. 1989,37,1. (11) Frommer, G.; SchBllhorn, H.; Thewalt, U.;Lippert, B. Inorg. Chem. 1990,29, 1417. (12) Abbreviations used: 1-MeC = neutral 1-methylcytosine;1-MeUH = neutral 1-methyluracil;1-MeU = 1-methyluracildeprotonated at N3; 9-MeGH = neutral 9-methylguanine; 9-MeG 5 9-methylguanine deprotonated at N1; en = ethylenediamine;dien = diethylenetriamine;ht = head-tail.
0020-1669/92/1331-2429$03.00/0
(13) (a) Dhara, S . C. Indian J . Chem. 1970,8, 193. (b) Raudaschl, G.; Lippert, B.; Hoeschele, J. D.; Howard-Lock, H. E.; Lock,C. J. L.; Pilon, P. Inorg. Chim. Acta 1985,106,141. (14) Arpalahti, J.; Lippert, B.; SchBUhom, H.; Thewalt, U.Inorg. Chim. Acra 1988,1 5 3 , 4 5 . (15) Basolo, F.; Bailar, J. C., Jr.; Tarr, B. R. J . Am. Chem. SOC.1950,72, 2433. (16) Watt, G. W.; Cude, W. A. Inorg. Chem. 1968,7, 335. (17) Lippert, B.; Neugebauer, D.;Raudaschl, G. Inorg. Chim. Acra 1983, 78,161. (18) Lippert, B.; Lock, C. J. L.; Speranzini, R. A. Inorg. Chem. 1981, 20, 335. (19) Kistenmacher, T. J.; Rossi, M.; Caradonna, J. P.; Marzilli, L. G. Adu. Mol. Relax. Interact. Processes 1979,IS,119. (20) Micklitz, W.; Lippert, B.; SchBllhorn, H.; Thewalt, U.J . Heterocycl. Chem. 1989,26, 1499.
0 1992 American Chemical Society
2430 Inorganic Chemistry, Vol. 31, No. 12, 1992
Frommer et al.
(2e): C, 16.5 (16.4); H, 3.5 (3.5); N, 16.9 (17.0). Anal. Calcd (found) Table I. Atomic Coordinates and Equivalent Isotropic Displacement for C2iH~i601&12Ptz(20: C, 21.3 (20.9); H, 3.4 (3.1); N, 18.9 (18.9). Parameters (A2 X lo4) of (en)Pt(9-MeG-Ni),.3H,0 (4a)" [(NH,),Pt( 1-MeC)(9-MeG-Ni,N')Pt(dien)](C10,),~2H20 (3) was Y Z X prepared by mixing an aqueous suspension of cis-[(NH&Pt( 1-MeC)CIICI (0.75 mmol in 100 mL of H20) with an aqueous solution of Pt 0.28956 (1) 0.53964 (1) 0.04763 (1) 225 AgClO, (1.48 mmol in 8 mL of H 2 0 ) and stirring it for 48 h at 20 'C 0.4676 (3) 0.0923 (1) 249 N(l) 0.2321 (3) in the dark. After filtration of AgCI, [(dien)Pt(9-MeGH-N')](C104)2 0.3444 (3) 0.0660 (1) 365 N(2) 0.2889 (3) (0.5 "01) was added (pH 4) and the mixture brought to pH 8 by means 0.3320 (3) 0.1199 (1) 294 N(3) 0.1996 (3) of 0.1 N NaOH. After 3 d at 70 'C, the solution was allowed to evap0.1855 (1) 295 0.4783 (3) N(7) 0.0944 (3) orate to a IO-mL volume and a small amount of hf-cis-[(NH,),Pt(l0.1794 (1) 310 0.3397 (3) N(9) 0.1080 (3) MeC)]2(C104)~1 was removed. The filtrate was passed over a Sephacryl 0.0020 (1) 230 0.4804 (3) N(11) 0.2234 (3) SlOO HR column and colorless cubes of 3 crystallized from the middle 0.0258 (1) 331 0.5441 (3) N(12) 0.1011 (3) fractions (14% yield). Anal. Cakd (found) for C15H36N13016C13PtZ: C, -0.0283 (1) 264 0.4532 (3) N(13) 0.0877 (3) 15.7 (15.5); H, 3.2 (3.2); N, 15.8 (15.5). 0.3388 (3) -0.0896 (1) 342 N(17) 0.2364 (3) ((en)Pt[(9-MeG-Nifl)Pt(dien)]2~(C104)4.2Hz0 (4) was prepared as 289 -0.0875 (1) 0.3605 (3) N(19) 0.0971 (3) (2.0 mmol) was added to an follows: [(dien)Pt(9-MeGH-N')](C104)2 0.6084 (3) 0.0904 (1) 342 N(20) 0.3541 (3) aqueous solution of [(en)Pt(H20),](C104)2(1 mmol in 40 mL of H,O; 0.0066 (1) 298 0.6192 (3) N(21) 0.3460 (3) prepared from enRCI, and AgCIO,), the pH adjusted to 8 by means of 355 0.1183 (1) 0.5896 (2) O(6) 0.1768 (2) NaOH and the mixture stirred for 4 d at 60 'C. The solution was then -0.0225 (1) 345 0.4219 (3) O(16) 0.3443 (2) concentrated to a 6-mL volume and passed over Sephadex G10. 4 was 0.1678 (1) 519 0.6950 (3) O(30) 0.2640 (3) isolated in 17% yield as a colorless powder from the final fractions. Anal. -0.0253 (1) 514 0.5929 (3) O(40) 0.5181 (3) Calcd (found) for C22H~N18020C14Pt3: C, 16.5 (16.5); H, 3.1 (3.1); N, 0.244 (6) 0.0616 (3) 1074 O(50) 0.506 (6) 15.7 (15.7); C1, 8.8 (8.8). 0.0936 (2) 275 0.3817 (3) C(2) 0.2389 (3) (en)Pt(9-MeG-N1)2.3H20( 4 4 was obtained from 4 (0.25 mmol in 0.1477 (2) 250 0.3746 (3) C(4) 0.1536 (3) 4 mL of H,O) and NaCN (2.50 mmol) after 1 h of reaction time at 20 0.1516 (2) 255 0.4604 (3) C(5) 0.1446 (3) OC. It was separated from unreacted NaCN, NaC104, and NaZPt(CN), 0.51 10 (4) 0.1214 (2) 265 C(6) 0.1837 (3) by size exclusion chromatography (Sephacryl SI00 HR) and isolated as 0.4054 (4) 0.2007 (2) 332 C(8) 0.0745 (3) colorless cubes in 50% yield. Anal. Calcd (found) for C14H26N1205Pt: 0.1890 (2) 456 0.2513 (4) C(9) 0.1067 (4) C, 26.4 (26.5); H, 4.1 (4.0); N, 26.4 (26.4). -0.0006 (2) 257 0.4905 (3) C(12) 0.1386 (3) cis&-((en)Pt [ (9-MeG-Ni,N')Pt( l-MeC)(NH3)2]2J(C104)4.9H20 C(14) -0.0551 (2) 250 0.4053 (3) 0.1312 (3) (4b) was obtained in 28% yield upon slow evaporation (30 "C) of a -0.0563 (2) 262 0.3915 (3) C(15) 0.2159 (3) mixture of 4 (0.04 mmol) and C~~-[(NH~)~P~(~-M~C)(H,O)](CIO,)~ -0,0260 (2) 262 0.4304 (3) C(16) 0.2664 (3) (0.08 mmol in 10 mL of H20, obtained from [(NH,),Pt(l-MeC)Cl]Cl 0.3223 (4) -0.1063 (2) 368 C(18) 0.1636 (4) and AgC104). Anal. Calcd (found) for C24H64N22029C14Pt3: C, 15.6 0.3614 (4) -0.1003 (2) 450 C(19) 0.0104 (4) (15.5); H, 3.5 (3.2); N, 16.6 (16.1). 0.0697 (2) 394 0.6711 (4) C(20) 0.4079 (4) Solution Studies. Reaction of 2a (0.01 mmol in 0.5 mL of D20) with 0.0306 (2) 383 0.6970 (4) C(21) 0.3666 (4) a mixture of C ~ S - [ ( N H ~ ) ~ P ~ ( Dand ~ O cis-(NH3),PtCl2 )~]~+ (prepared from 0,Ol mmol of cis-(NH3),PtC1, and ca. 0.018 mmol of AgN03 in 0.1 mL of D20) led to rapid formation of three products which, on the The structure was solved via a Patterson function and Ap maps. It was basis of pD dependent IH NMR spectroscopy, were assigned to cis,refined (on F) using full-matrix least-squares methods with anisotropic cis-[(NH3),(1-MeU)Pt(9-MeG-~i,N')Pt(NH~)2(DzO)](ClO4)z (Zb), displacement parameters for all non-H atoms and a common isotropic cis,cis-[(NH3),( l-MeU)Pt(9-MeG-N1,N')Pt(NH3)2C1]C104 (k), and displacement parameter for the H atoms, which were placed in geome(M). cis,cis,cis-([(NH3)2(l-MeU)Pt(9-MeG-N1,N')]2Pt(NH3)~J(C104)2 trically calculated positions (C-H = 0.96 A; N-H = 0.90 A). A total Addition of excess NaCl to the mixture converted 2b quantitatively to of 289 parameters were refined. Weights w = l.O/($(F) + (O.ooOo2P)) 2c. led to a featureless analysis of variance in terms of sin 8 and F,. The cis-[(NH3),Pt(1-MeC)(9-MeG-Ni)]ClO4 ( 3 4 was prepared by re= refinement converged to S = 1.27, R = 0.027, R, = 0.022, (A/&, action of 3 (0.01 mmol) in 0.55 mL of DzO) with NaCN (0.08 mmol) 0.07 (except for atom O(50) which had 0.05 1 (A/u) I 1.2) (no exwithin 1 h at 20 OC in 100% yield but later decomposed in the presence tinction correction). The correctness of the space group choice was of excess CN-. checked by using M I S S Y M . ~ ~ The largest peaks in final Ap map were Spectra. IR spectra were recorded on a Perkin-Elmer 580 B instruh0.7 (3) e A-'. Atomic scattering factors for neutral atoms and real and ment on KBr pellets and Nujol mulls. IH NMR spectra were taken on imaginary dispersion terms were taken from ref 23. The programs used a Bruker AC 200 instrument for complexes in D 2 0 with TSP and/or were PAR ST,^^ SHELXTL PLUS,^^ PLAT ON,^^ and M I S S Y M . ~ ~Positional pa[NMe4]+(3.19 ppm downfield from TSP) as internal reference. 8 values rameters and the equivalent values of the anisotropic displacement paare given relative to TSP. Occasionally, e.g., with 2f and 4b, TSP (3rameters for the non-H atoms are given in Table I. (trimethylsily1)- 1-propanesulfonate, Na+ salt) proved an unreliable internal reference, in contrast to [NMe4]+. pH-dependent NMR shifts Results and Discussion were determined using uncorrected pH* values. Metbod of Preparation of Cbmpouads. The preparation of N1 CrystaUography. A crystal of 4a (0.5 X 0.2 X 0.15 mm) was mounted or N7,N 1 platinated 9-methylguaninecomplexes is schematically in a Lindemann glass capillary. Intensity data were collected at T = outlined in Figure 1. The starting material in all cases was 291(1) K with w/28 scans, variable scan speed 2.5-15.0' m i d in 8, and [(dien)Pt(9-MeGH-N)]*+J1 which was reacted at neutral or scan width 1.2' + dispersion. A Nicolet R3m/V diffractometer with slightly alkaline pH with a second Pt electrophile such as the graphite-monochromated Mo Ka radiation (A = 0.71073 A) was used for preliminary examinations and data collection. The lattice parameters monofunctional [(dien)Pt(H,O)]Z+, cis-[(NH,),Pt( 1-MeUwere determined from a symmetry-constrained least-squares fit of 25 IP)(H,O)]+, and C~~-[(NH~)~P~(~-M~C-N~)(H~O)]~ or the reflections with 28,, = 19.35'. Crystal data are as follows: CI4Hz6bifunctional [(en)Pt(H20)2]2+to give the di- and trinuclear species NI2OSPt,fw = 637.53, tetragonal system, space group 14,/a, a = 16.003 [ (dien)Pt (Nl-9-MeG-N)Pt(dien)] 3+, 1, cis-[(NH3),( 1-MeU(2) A, c = 32.247 (6) A, V = 8258 (2) A', Z = 16, d,, = 2.051 g cm3. IP)Pt(N1-9-MeG-N)Pt(dien)] 2+, 2, cis-[(NH3),( 1-MeC-N3)w scans of low-order reflections along the three crystal axes showed Pt(Ni-9-MeG-hn)Pt(dien)l3+, 3, or {(en)Pt[(N1-9-MeG-N7)Ptacceptable mosaicity. Six standard reflections (5,-2,5; -5,2-5; 1,-6.2; -1,6-2; 0,0,12; O,O,-12) were recorded every 300 reflections, only random deviations were detected during 448.12 h of X-ray exposure; 25 792 Le Page, Y. J. Appl. Crystallogr. 1987, 20, 264. reflections with 1.0' I 28 I 50.0°, -20 I h I 20, -20 I k 110, and -39 Cromer, D. T.; Waber, J. T. International Tables for X-ray Crystali I I 39 were measured. The data were corrected for Lorentz-polarilography; Ibers, J. A., Hamilton, W. C., Eds.; Kynoch Press: Birzation but not for absorption effects (g = 6.9 mm-l) and averaged (Rin, mingham, England, 1974; Vol. IV. = 0.033) to 3661 unique reflections, 2937 of which had F 1 4.Ou(F). The (24) Nardelli, M. Comput. Chem. 1983, 7, 95. (25) Sheldrick, G. M. SHELXTL Plus, release 3.4. An InfegratedSystemfor systematic absences (hkl) h + k + I = 2n + 1, (hkO) h = 2n + 1, and Solving, Refining and Displaying Crystal Structurefrom Diffracrion (001)I = 4n + 1, I = 4n + 2, and = 4n + 3 conform to space group 14,/a. Dara. For Nicolet R3mJ V Crystallographic Systems; University of Gottingen: Gottingen, Germany, 1987. (21) Compound identified by :H NMR and IR: Faggiani, R.; Lippert, B.; (26) Spek,A. L. In Computational Crystallography; Sayre, D.,Ed.; Claredon Press: Oxford, England, 1982; p 528. Lock, C. J. L.; Speranzini, R. A. J. Am. Chem. SOC. 1981, 103, 1111.
Inorganic Chemistry, Voi. 31, No. 12, 1992 2431
Platinum(I1) Coordination
Table 11. Chemical Shifts of 9-Methylguanine (9-Methylguaninato) Resonances in the Pt Complexes rotation pD H8 CH, aboutR-N7 Pt(9-MeGH-N) [dienPt(9-MeGH-N')I2+ . 2-7 8.12 3.70 2f 2-7 8.23 3.64 medium
n
H-N1 N7
CN-
CN-
CN-
1
I
4
t
XN1nN7
N7 N l M N7
mixture
Xn
U
N1 N7
C
FN-
e n
bo
Pt(9-MeG-",N1)Pt 3-10 7.96 3-10 7.96 8.00 5 3-10 7.97 3-10 7.79 3-10 7.85 3-10 7.95 3-10 7.98 3-10 7.95 3-10 7.87 7.86 7.84
3.67 3.66 3.64 3.63 3.54 3.62 3.57 3.65 3.64 3.61 3.60 3.59
2a 38 4s
Pt(9-MeG-N') 7.55 >6 >6 7.66 7.52 >6
3.54 3.61 3.47
2g
Pt(9-MeGH-N')
