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Syntheses are reported for: nine 2-nitroimidazoles, the abbreviated names all beginning with E, based on derivation from Etanidazole); five 2-methyl-5-nitroimidazoles (M compounds, derived from Metronidazole); and five 2-methyl-4-nitroimidazoles (labelled 2M4N compounds). The nitroimidazoles all have an amide side-chain at the N1 atom of the imidazole, with 17 of them containing one to five halogen atoms. The aim is to study compounds for comparison with EF5 (the number showing the presence of five F-atoms), a previously reported, pentafluoropropylacetamide derivative of 2-nitroimidazole that is currently used as a hypoxia marker drug to detect cancerous tumours. The new compounds are characterized by standard methods, including X-ray structural data for the fluorinated MF5, 2M4NF5, and 2M4NF1(−1) species, with the “–1” indicating two C-atoms in an alkylamide chain rather than the three C-atoms in the propylacetamide of EF5. Intra- and inter-molecular H-bonding is seen in the solid state structures, likely an important property in biological use; another key property of the nitroimidazoles is their reduction potentials, and the measured CV data confirm that 2NO2Im compounds with longer side-chains and more F-atoms (like EF5) are worth investigating for possible activity as hypoxia-selective, bioreductive agents.

The Ru III complexes, [Ru(acac) 2 L 2 ] Tf, and the Ru II complexes, Ru(hfac) 2 L 2 , have been synthesized and characterized; acac = acetylacetonate, hfac = 1,1,1,5,5,5-hexafluoroacetonate, Tf = triflate, and L = imidazole (Im) or a substituted imidazole (NMeIm, 2MeIm, 4/5MeIm, 2NO 2 Im); other nitroimidazoles, named metronidazole, etanidazole, and EF5 (a pentafluorinated derivative of etanidazole) were also used. Cis -isomers of the Ru complexes were usually formed, but some trans -isomers were also isolated. Characterization methods include NMR, UV/Vis, and MS spectroscopies, and CV data; X-ray crystallographic data were obtained for the cis -[Ru(acac) 2 L 2 ]Tf complexes (L = Im, NMeIm, 2MeIm, and 5MeIm). Interest in these complexes stems from their potential antiproliferatory activity, and use of the nitroimidazole species as radiosensitizers. More incidentally synthesized were cis -[Ru(acac) 2 L(MeCN)]Tf (L = Im, 2MeIm), cis -Ru(hfac) 2 Im(MeCN), and [Ru(hfac)(NMeIm) 4 ]PF 6 .

The synthesis of four new oxorhenium(V) complexes containing the “3 + 1” mixed-ligand donor set, ReO(SYS)X (where Y = S, py; X = Cl, Br), is described. All of the complexes tested exhibited selectivity for cathepsin B over K. Most notably, compound 6, ReO(SSS-2,2‘)Br (IC50(cathepsin B) = 1.0 nM), was 260 times more potent against cathepsin B. It was also discovered that complexes containing the same tridentate (SSS) ligand were more potent when the leaving group was bromide versus chloride (e.g., IC50(cathepsin B): ReO(SSS-2,2‘)Cl (4), 8.8 nM; ReO(SSS-2,2‘)Br (6), 1.0 nM). Mechanistic studies with cathepsin B showed that both compounds 2 (ReO(SpyS)(SPhOMe-p)) and 4 were active-site-directed. Compound 2 was determined to be a tight-binding, reversible inhibitor, while compound 4 was a time-dependent, slowly reversible inhibitor. The results described in this paper show that the oxorhenium(V) “3 + 1” complexes are potent, selective inhibitors of cathepsin B and have potential for the treatment of cancer.

The synthesis of several new oxorhenium(V) complexes containing the ‘3 + 1’ mixed-ligand donor set, ReO(SXS)(SR) (where X = S, O, N(R′); R = alkyl, aryl, heterocylce; R′ = H, alkyl, aryl), is described. The X-ray structure for four of these complexes ReO(SN(Ph)S)(SPh) ( 6 ), ReO(SN(CH 2 CH 2 NMe 2 )S)(SPhOMe- p ) ( 10 ), ReO(SOS)(SPh) ( 29 ) and ReO(SOS)(SPhNO 2 - p ) ( 30 ) was determined. The inhibitory activity of all of the oxorhenium(V) complexes reported herein was evaluated against the cysteine proteases cathepsin B and K in vitro. Compound 25 , ReO(SSS)(S-4py) · HCl, was the best inhibitor of the series against cathepsin B with an IC 50 of 10 nM. Several of the complexes exhibited specificity for cathepsin B over K, suggesting that oxorhenium(V) complexes can be designed to be enzyme specific. The results described in this paper show that the oxorhenium(V) ‘3 + 1’ complexes are potent inhibitors of cathepsin B and K, constituting promising potential for the treatment of cancer and osteoporosis, respectively.

The complexation chemistry of several dithiocarbamates (dtc) (KS2CProOMe, KS2CProK, KNMeIleK) with [Ru(β-diketonato)2(MeCN)2][CF3SO3] (β-diketonato=acac (2,4-pentanedionato) and dpac (1,3-diphenyl-1,3-propanedionato)) was investigated. It was discovered that the dtc underwent some unusual and unprecedented CS2-elimination chemistry to yield chelated imino or amino acidato Ru(III) complexes. For the proline case, both the KS2CProOMe and KS2CProK dtc yielded two products, the chelated dithiocarbamato complexes Ru(β-diketonato)2(dtc) (dtc=S2CProOMe or S2CProK) and the CS2-eliminated imino prolinato complexes Ru(β-diketonato)2(Pro-H2) (β-diketonato=acac (10) and dpac (14)) for which the crystal structures have been determined. For the N-methylisoleucine case, KS2CNMeIleK yielded only the CS2-eliminated amino N-methylisoleucinato complexes Ru(β-diketonato)2(NMeIle). The X-ray structure for Ru(acac)2(NMeIle) (16) was determined. The direct reaction of the amino acids (Pro or NMeIle) with [Ru(β-diketonato)2(MeCN)2][CF3SO3] yielded [Ru(dpac)2(Pro)]2 and [Ru(acac)2(NMeIle)]2, the first examples of paramagnetic μ-amino acidato bridged Ru(III) dimers which could be converted to their corresponding chelated amino acidato monomeric complexes upon treatment with base. The formal potentials of all of the Ru(III) complexes reported were determined by cyclic voltammetry.

We report on the preparation of a hypoxia marker 2-(2-nitroimidazol-1[H]-yl)- N -(3-fluoropropyl)acetamide (EF1) and its 18 F analog, 2-(2-nitroimidazol-1[H]-yl)- N -(3-[ 18 F]fluoropropyl)acetamide ([ 18 F]-EF1). Two methods for the preparation of 3-fluoropropylamine, the EF1 side chain, are described. [ 18 F]-EF1 was prepared with a radiochemical yield of 2% by nucleophilic substitution of bromine in 2-(2-nitroimidazol-1[H]-yl)- N -(3-bromopropyl)acetamide (EBr1) by carrier-added 18 F in DMSO at 120°C. Our results demonstrate the preparation of clinically relevant amounts of [ 18 F]-EF1 for use as a non-invasive hypoxia marker with detection using positron emission tomography (PET).

Ru(hfac)3 (2) was synthesized via peroxide oxidation of the Ru(II) species [Na][Ru(hfac)3] (1) (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate). Treatment of either 1 or 2 with CF3SO3H in MeCN generated cis-Ru(hfac)2(MeCN)2 (3). Ru(acac)2(hfac) (4) (acac = acetylacetonate) was generated by addition of hfac to an EtOH solution of cis-[Ru(acac)2(MeCN)2][CF3SO3]. Subsequent treatment of 4 with CF3SO3H in MeCN yielded cis-Ru(acac)(hfac)(MeCN)2 (7). Syntheses of [Na][Ru(hfac)2(acac)] (5) and Ru(hfac)2(acac) (6) are also reported. The complexes were characterized generally by elemental analysis, cyclic voltammetry, UV-vis, NMR, and IR spectroscopies. The structures of 2, 3, and 7 were established by X-ray crystallographic analyses. Crystals of 2 are monoclinic with a = 8.7781(4), b = 13.0760(11), c = 19.1857(5) Å, β = 92.2275(5)°, Z = 4, and space group P21/n; those of 3 are monoclinic with a = 25.731(4), b = 8.8332(13), c = 18.1955(4) Å, β = 93.3395(6)°, Z = 8, and space group C2/c; and those of 7 are triclinic with a = 7.6812(9), b = 10.680(2), c = 12.578(2) Å, α = 88.062(6)°, β = 83.874(3)°, γ = 69.5898(15)°, Z = 2, and space group Pbar over 1. The structures were solved by Patterson methods and refined by full-matrix least-squares procedures to R(F) = 0.036, 0.035, and 0.068 (Rw(F2) = 0.061,Rw(F) = 0.052, and Rw(F) = 0.089), respectively.Key words: ruthenium, β-diketonato complexes, acetylacetonate, 1,1,1,5,5,5-hexafluoroacetylacetonate, acetonitrile complexes.

[Ru(II)(L)6]2+ complexes were synthesized from [Ru(DMF)6][CF3SO3]3; DMF = dimethylformamide, L = imidazole (Im), N-methylimidazole (NMeIm) and 5-methylimidazole (5MeIm). The 2-methylimidazole complex trans-[Ru(CO)(DMF)(2MeIm)4][CF3SO3]2 (4) was also synthesized via a reaction involving abstraction of CO from DMF; 4 loses CO reversibly at ambient temperature to form [Ru(DMF)(2MeIm)4][CF3SO3]2 (5), and the DMF can be removed to generate a [Ru(CF3SO3)x(2MeIm)4][CF3SO3]y species (x = 2, y = 0, or x = 1 = y), containing coordinated triflate. The complexes were characterized by elemental analysis, conductivity, UV-vis, NMR, and IR spectroscopies. The structures of [Ru(Im)6][CF3SO3]2 (1), [Ru(NMeIm)6][CF3SO3]2 (2), and [Ru(5MeIm)6][CF3SO3]2 (3) were established by X-ray crystallographic analyses. Crystals of 1, are triclinic, a = 7.4010(6), b = 9.9846(15), c = 11.275(2) Å, α = 113.469(5), β = 92.419(2), γ = 94.737(2)°, Z = 1, space group P1 ; those of 2, are trigonal, a = 11.558(2), c = 8.109(3) Å, Z = 1, space group P3; and those of 3, are trigonal, a = 12.6547(4), c = 20.4078(12) Å, Z = 3, space group R3. The structures were solved by Patterson methods and refined by full-matrix least-squares procedures to R(F) = 0.029, 0.034, and 0.034 (R w (F2) = 0.055, R w (F) = 0.031, and R w (F2) = 0.058), respectively. Key words: hexakis(imidazole)ruthenium(II) triflates, crystal structures, CO abstraction.

EF5 (a 2-nitroimidazole containing an N-(pentafluoropropyl) acetamide substituent) is a very sensitive probe for quantifying the amount of hypoxia within cells; a much improved, short step, synthetic procedure is described for EF5, whose X-ray structure is also presented.

The paramagnetic, S = 1, NiX 2 L 2 (X  Cl or Br, L  PPh 3− n py n , n = 1–3), and diamagnetic NiBr 2 [d(py)pe] ( 4b ) complexes have been isolated, generally as solvates, where py = 2-pyridyl and d(py)pe = py 2 P(CH 2 ) 2 Ppy 2 . Also isolated are the diamagnetic Ni(CO) 2 (PPh 2 py) 2 ( 5 ), Ni(CO) 2 [d(py)pe] ( 7 ), Ni(PPh 2 py) 4 , Ni(PPhpy 2 ) 4 and Ni[d(py)pe] 2 , sometimes as hydrates. The complexes, except for 5 which contains paramagnetic impurities, analyze well, and have been characterized by 1 H and 31 P{ 1 H} NMR (for diamagnetic species), IR (for the carbonyls) or magnetic moment data (for the paramagnetic species). NMR evidence for in situ formation of Ni(CO) 2 (PPhpy 2 ) 2 and Ni(Ppy 3 ) 4 is also presented. Of note, NiX 2 L 2 , 4b and 7 are water-soluble, possibly because of protonation of the pyridyl-N atoms, although this remains to be established; even non-aqueous solutions of these Ni(II) species are moisture-sensitive. In contrast to Ni(PPh 3 ) 4 , at ambient conditions the NiL 4 species show little tendency to dissociate in benzene or toluene.

EF5 (a 2-nitroimidazole containing an N-(pentafluoropropyl) acetamide substituent) is a very sensitive probe for quantifying the amount of hypoxia within cells; a much improved, short step, synthetic procedure is described for EF5, whose X-ray structure is also presented.

Erratum to ‘‘Metal compounds for the treatment of parasitic diseases” [J. Inorg. Biochem. 102 (2008) 1839–1845] Simon P. Fricker *, Renee M. Mosi , Beth R. Cameron , Ian Baird , Youngbao Zhu , Virginia Anastassov , Jennifer Cox , Patricia S. Doyle , Elizabeth Hansell , Gloria Lau , Jonathan Langille , Micki Olsen , Ling Qin , Renato Skerlj , Rebecca S.Y. Wong , Zefferino Santucci , James H. McKerrow c