Synthesis, photophysical properties and sugar-dependent in vitro photocytotoxicity of pyrrolidine-fused chlorins bearing S-glycosides

Eight S-glycosylated 5,10,15,20-tetrakis(tetrafluorophenyl)porphyrins (1a′, 1b′, 1a and 1b (a: S-glucosylated, b: S-galactosylated)) and their 1,3-dipolar cycloadducts, i.e. chlorins 2a′, 2b′, 2a and 2b were prepared by nucleophilic substitution of the pentafluorophenyl groups with S-glycoside. These photosensitizers were characterized by ¹H, ¹³C and ¹⁹F NMR spectroscopies and elemental analysis. The photocytotoxicity of the S-glycosylated photosensitizers and the parent porphyrin (1) and chlorin (2) was examined in HeLa cells. Photosensitizers 1, 2, 1a′, 1b′, 2a′ and 2b′ showed no significant photocytotoxicity at the concentration of 0.5 μM, while the deprotected photosensitizers 1a, 1b, 2a and 2b were photocytotoxic. The strong inhibition by sodium azide of the photocytotoxicity of these photosensitizers suggested that ¹O₂ is the main mediator. The S-glucosylated photosensitizers 1a and 2a showed higher photocytotoxicity than S-galactosylated 1b and 2b, respectively. The cellular uptake of 1a and 2a increased up to 24 h, while that of 1b and 2b was saturated by 12 h.     

Synthesis of new chiral keto alcohols by baker’s yeast

Fourteen chiral α- and β-keto alcohols 2a–2r were synthesized by the asymmetric reduction of their corresponding diketones 1a–1r via baker’s yeast. In addition, ten corresponding racemic α-keto alcohols were synthesized by the benzoin condensation of their corresponding aldehydes, which were used for the determination of the ee values through their chiral resolution on chiral HPLC. Amongst the 15 diketones, 1j and chiral α-keto alcohols 2i, 2j and chiral β-keto alcohol 2r are novel compounds. Six keto alcohols 2b, 2c, 2d, 2f, 2h and 2p were synthesized by baker’s yeast for the first time. There are some studies in the literature where baker’s yeast was applied to the diketones 1a, 1g, 1e, 1k and 1n under various conditions different to those reported herein. The yields and the ee values of these studies were not as high as ours. All of the keto alcohols synthesized were characterized by IR, NMR (¹H and ¹³C), and MS. The relationship between the structure of the diketone and the yield, diastereoselectivity and enantiomeric excess is also discussed.     

Kinetic resolution of 1-(benzofuran-2-yl)ethanols by lipase-catalyzed enantiomer selective reactions

Kinetic resolution of racemic 1-(benzofuran-2-yl)ethanols rac-1a–d was performed by lipase-catalyzed enantiomer selective acylation (E≫100) yielding (1R)-1-acetoxy-1-(benzofuran-2-yl)ethanes (R)-2a–d and (1S)-1-(benzofuran-2-yl)ethanols (S)-1a–d in highly enantiopure form. The degree of enantiomer selectivity for enzymatic alcoholysis/hydrolysis processes starting from racemic 1-acetoxy-1-(benzofuran-2-yl)ethane rac-2 was also tested under various conditions including supercritical CO₂ medium. Racemization-free lipase-catalyzed ethanolysis of the (1R)-1-acetoxy-1-(benzofuran-2-yl)ethanes (R)-2a–d yielded almost quantitatively the enantiopure (1R)-1-(benzofuran-2-yl)ethanols (R)-1a–d.     

New benzimidazole derivatives: Design,synthesis, docking,and biological evaluation

The aim of this study was to synthesize novel enaminonitrile derivatives starting from 2-aminobenzimidazole and utilize this derivative for the preparation of novel heterocyclic compounds and assess their function for biological activity screening. The key precursor N-(1H-benzo[d]imidazol-2-yl)carbonohydrazonoyl dicyanide (2) was prepared in pyridine by coupling of diazotized 2-aminobenzimidazole (1) with malononitrile. Compound 2 was subjected to react with various secondary amines such as piperidine, morpholine, piperazine, diphenylamine, N-methylglucamine, and diethanolamine in boiling ethanol to give the acrylonitriles (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(piperidin-1-yl)acrylonitrile (3), (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-morpholinoacrylonitrile (4), (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(piperazin-1-yl)acrylonitrile (5), (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(diphenylamino)acrylonitrile (6), (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(methyl((2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexyl)amino)acrylonitrile (7), and (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(bis(2-hydroxyethyl)amino)acrylonitrile (8), respectively. It has been found that the behaviour of nitrile derivative 2 towards hydrazine hydrate to the creation of 4-((1H-benzo[d]imidazol-2-yl)diazenyl)-1H-pyrazole-3,5-diamine (9). The reaction of malononitrile with compound 2 in an ethanolic solution catalyzed with sodium ethoxide afforded 4-amino-1-(1H-benzo[d]imidazol-2-yl)-6-imino-1,6-dihydropyridazine-3,5-dicarbonitrile (11). Moreover, malononitrile reacted with 7 in a boiling ethanolic sodium ethoxide solution to give 2-(5-((1H-benzo[d]imidazol-2-yl)diazenyl)-4-amino-6-(methyl((2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexyl)amino)pyrimidin-2-yl)acetonitrile (14). Heating 7 in boiling acetic anhydride and pyridine afforded (2R,3R,4R,5S)-6-(((1E)-2-((1-acetyl-1H-benzo[d]imidazol-2-yl)diazenyl)-1-(N-acetylacetamido)-2-cyanovinyl)(methyl)amino)hexane-1,2,3,4,5-pentayl pentaacetate (15). When compound 15 is heated for a long time in refluxing DMF including a catalytic of TEA, cyclization occurs to give the corresponding (2R,3R,4R,5S)-6-((1-acetyl-3-((1-acetyl-1H-benzo[d]imidazol-2-yl)diazenyl)-4-amino-6-oxo-1,6-dihydropyridin-2-yl)(methyl)amino)hexane-1,2,3,4,5-pentayl pentaacetate (16). In addition, triethyl orthoformate was reacted with compound 7 in the presence of acetic anhydride to afford the corresponding ethoxymethyleneamino derivative (2R,3R,4R,5S)-6-(((1E)-2-((1-acetyl-1H-benzo[d]imidazol-2-yl)diazenyl)-2-cyano-1-(((E) ethoxymethylene)amino)vinyl)(methyl)amino)hexane-1,2,3,4,5-pentayl pentaacetate (17). Also, it has been found that heating a mixture of 7 with DMF/DMA in anhydrous xylene yielded compound (1E)-N'-((1E)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-2-cyano-1-(methyl((2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexyl)amino)vinyl)-N,N-dimethylformimidamide (18). In addition, compound 7, when reacted with several acid anhydrides, allowed the matching phthalimide derivatives 19–26. The results showed that compound 14 has significantly higher ABTS and antitumor activities than the other compounds. Molecular modelling was also studied for compounds 22 and 24. The viability of four many cell lines—the African green monkey kidney epithelial cells (VERO), human breast adenocarcinoma cell line (MCF-7), human lung fibroblast cell line (WI-38), and human hepatocellular liver carcinoma cell line (HepG2) was examined to determine the antitumor activities of the newly synthesized compounds. Also, it was found that compounds 9, 11, 15, 16, 22, 23, 24 and 25 are strong against HepG2 cell lines, while 16, 22, and 25 are strong against WI-38 cell lines. Moreover, it was also found that compounds 16 and 22 are strong against VERO cell lines. On the other hand, compounds 7, 14, 15, 16, and 22 are strong while the rest of the other compounds are moderate against the MCF-7 cell line. The result of docking showed that compound 24 got stabilized inside the pocket with a very promising binding score of ? 8.12 through hydrogen bonds with Arg184 and Lys179, respectively.     

The structures of macbecin I and II : New antitumor antibiotics

Macbecin I 1, C₃₀H₄₂N₂O₈, and macbecin II 2, C₃₀H₄₄N₂O₈, were shown to be 2,6-disubstituted benzoquinone and hydroquinone derivatives by an oxidation-reduction relationship, UV. ¹H and ¹³C NMR spectra. Alkaline methanolysis of 1 gave a 2-aminobenzoquinone derivative 5, suggesting an ansa-structure for 1, and acid hydrolysis of 1 gave decarbamoyl products 9,10 and 11, indicative of the location of carbamoyloxy group in allylic position. Spin decoupling studies on 1,3 and 5clarified the partial structures [A], [B], [C] and [D]. From their mutual disposition two structures 1a and 1b, were proposed out of which 1a has been selected for the structure of 1 on the basis of the structure of oxidative degradation product 12. X-Ray analysis of the bromoacetyl derivative of 1 confirmed the above proposed structure and determined the absolute stereochemistry of 1 and 2.     

Solvent-dependent reactivities of acyclic nitrones with β-diketones: catalyst-free syntheses of endiones and enones

Reactions of the nitrones ^?O⁺N(Me)C(H)Ar 1 (Ar=phenyl 1a, 4-methylphenyl 1b, 2,4,6-trimethylphenyl 1c, and anthracen-9-yl 1d) with the cyclic β-diketones 1,3-indandione 2 or barbituric acid 3 in CH₂Cl₂, afford the corresponding endiones 2′a–2′d or 3′a–3′d. In contrast, dimedone 4 reacts with 1a or 1b to give the endione 4′a or 4′b and the bis-adduct 4″a or 4″b. Nevertheless, reaction of 4 with 1c or 1d in CH₂Cl₂ furnishes only the endione adducts 4′c or 4′d. However, the reaction of 4 with 1a or 1b in methanol gives only 4″a or 4″b, respectively. Among acyclic β-diketones only malonic acid 7 reacts with 1a–1c. Reaction of 7 with 1a in CH₂Cl₂ forms cinnamic acid 7″a, whereas in the case of 1b, the endione 7′b and (E)-3-p-tolylacrylic acid 7″b are obtained. The nitrone 1c reacts with 7 in CH₂Cl₂ to afford the endione 7′c or with acetone yielding (E)-4-mesitylbut-3-en-2-one 8. X-ray analyses are reported for 4′c, 5, and 7″b. In addition, the calculated acidity of the hydrogen at the α-C atom is shown to correlate with the reactivity of the β-diketones with nitrones.     

Resolution of 1-arylalkylamines with 6-(1,2:3,4-di-O-isopropylidene-α-d-galactopyranosyl)hydrogen phthalate

The resolving ability of a new acidic resolving agent, the hydrogen phthalate of 1,2:3,4-di-O-isopropylidene-α-d-galactopyranose 1, against various 1-arylalkylamines 2a–k is described. Treatment of 1 with amines 2a–f to obtain diastereomeric salts 1·(S)2a–f in 2-propanol allowing the corresponding (S)-amines 2a–f to be recovered in good yield and 61–89% ee. Recrystallization in dichloromethane/hexane, and regeneration gave the amines in enhanced enantiomeric purity (>98% ee). 1 resolved 1-phenylpropylamine 2f in high enantiomeric purity (99% ee) than 1-phenylethylamine 2g (11% ee) and o- and m-methoxy 2h–i, o-chloro-2j and p-fluoro-2k substituted 1-arylamines (11–19% ee). A possible chiral recognition mechanism based on the ability of 1 to exist in two conformations is described.     

Bromination of 3-phenylindoles

Brominations of 3-phenylindole (1a) and its 1-methyl-(1b) and 1-acetyl-(1c) derivatives with NBS in AcOH and CCl₄ have been carried out. In AcOH 1 gave 2-bromo derivatives (2) in high yields and the relative reactivity was found to be NH > NMe ? NAc by competitive reactions. In boiling CCl₄1a and 1b gave 2 but bromination of 1c did not proceed. Bromination of 1a with 2 moles of NBS in AcOH gave 2,6-(major) and 2,5-dibromides (8 and 9). Reaction of 2a with thiourea gave 19. Selective reduction of the bromine atom at the 2-position in 2,6-dibromide (10) was achieved by Zn3CuNaOH, and irradiation of 8 in EtOH-alkali reduced 2,6-dibromide to 1a.     

Electronic structures and thermolyses of 2-tetrazenes

The electronic structures and gas phase thermolyses of the cyclic 2-tetrazenes 2 and 3 and of open chain 1,1,4,4-tetramethyl-2-tetrazene (1) have been studied by photoelectron spectroscopy. While the six-membered ring compound 2 yields 1-methylmethylenamine (6) and nitrogen as fragments, the seven-membered ring compound 3 is contracted to 1,2-dimethylpyrazolidine (11). The acyclic 2-tetrazene 1 prefers disproportionation to 6 and dimethylamine (7). Based on MNDO calculations the tonization potentials of 1–3 were assigned to molecular orbitals. Several conformations of 2 and 3 were calculated. Compound 2 shows a rigid boat conformation with equatorial methyl groups, while 3 can occupy several conformations of similiar energies. The different thermal decompositions of 1– 3 are explained.     

(Pyrazol-1-ylmethyl)pyridine palladium complexes: Synthesis,molecular structures,and activation of small molecules

Reactions of 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1) and 2-(3,5-di-tert-butylpyrazol-1-ylmethyl)pyridine (L2) with either [PdClMe(COD)] or [PdCl₂(COD)] gave the mononuclear palladium complexes [PdCl₂(L1)] (1), [PdClMe(L1)] (2) [PdCl₂(L2)] (3) and [PdClMe(L2)] (4) in good yields. All compounds were characterized by NMR spectrometry, mass spectrometry, elemental analyses and also by single crystal X-ray crystallography for complexes 1, 3, and 4. The reaction of 2 with NaBAr₄ in NCMe gave the salt, [[PdMeNCMe(L3)]BAr₄ (5), in good yield. This salt was used as a catalyst to oligomerize ethylene at high pressures to branched polyethylene, but catalytic activity was low. The reaction of 2 with SO₂ and CO formed the respective insertion products [PdClS(O)₂Me(L1)] (6) and [PdClC(O)Me(L1)] (7).     

Resolution of β-unsaturated amines with isopropylidene glycerol hydrogen phthalate

1-Phenyl-2-propenylamine 2, 1-phenyl-2-propinylamine 3, 1-(1-cyclohexenyl)ethylamine 4, (E)-2-ethylidenecyclohexylamine 5 and α-methylallylamine hydrochloride 6 were selected as candidates for resolution with isopropylidene glycerol hydrogen phthalate 1, previously described as an efficient resolving agent of 1-arylalkylamines. With only the exception of 5, all these substrates were resolved by (S)-1. In particular both the enantiomers of 2 and 3 were obtained in excellent yields and with very high enantiomeric excesses. The absolute configurations of non-racemic forms of 2, 3 and 4, not prepared before except those of 3, were established by correlation with the respective hydrogenation products. The enantiomeric excesses of all the resolved substrates were accurately determined by chiral HPLC analysis. The fact that 1 resolves 4 and 6 but not their saturated analogues and shows higher efficiency in resolving 2 and 3 than 1-phenylpropylamine indicates the positive influence of the presence of β-unsaturation on the resolvability of aminic substrates with such an acid.     

Enantiopure tert-butyl(phenyl)phosphine oxide. Chirality-recognition ability and mechanism

When enantiopure tert-butyl(phenyl)phosphine oxide 1 was used as a resolving agent, it showed an acceptable to good chirality-recognition ability for several kinds of racemic carboxylic acids 2. A study on a chirality-recognition mechanism based on X-ray crystallographic analyses of the diastereomeric complexes of 2 with 1 revealed that the complex crystals consisted of helical columns and that 1 was not responsible for the formation of the helical column and occupied a void between the columns; although 1 interacted with 2 via a hydrogen bond to primarily form a pair with 2, the complex crystals were mainly stabilized by the accumulation of weak interactions, such as CH/π, π/π and CH?O interactions, between 1/1, 1/2 and 2/2.     

Two pairs of new alkaloid enantiomers with a spiro [benzofuranone-benzazepine] skeleton from the bark of Juglans mandshurica

(±)-Juglanaloid A (1) and B (2), two pairs of novel naturally occurring alkaloid enantiomers bearing an unprecedented spiro [benzofuranone-benzazepine] skeleton, were isolated from the bark of Juglans mandshurica Maxim. The unusual 6, 5, 7, 6-cyclic system with a rare spiro cyclic center at C-4 was determined on the basis of spectroscopic data. Chiral separation of 1 and 2 yielded two pairs of enantiomers, 1a/1b and 2a/2b. The absolute configurations were established by comparing the experimental and calculated electronic circular dichroism spectra. The potential anti-AD properties of 1a/1b and 2a/2b were evaluated by the Thioflavin T assay.     

Functionalized enamines—XIV : Reaction of α-tetralone enamines with carbenes influence of the nature of carbene and the base-component of the enamine on the reaction pattern

Enamine Ia, derived from 6-methoxy-1-tetralone and morpholine, reacts with carbenes¹2a and 2b to give (1:1) adducts 3a, and a mixture of 3b and 3c, respectively. The pyrrolidine enamine 1b, on the other hand, reacts with carbene 2b, to give, beside the (1:1) adduct 3e, benzylidene-derivative 4b. Reaction of enamine 1b with carbene 2a does not yield a 1:1 adduct; instead, two products were isolated which have been identified as 4a and 5. Both morpholine and pyrrolidine enamines 1ab, react with carbene 2c to give one and the same product 6. Possible mechanisms for the formation of the reaction products are discussed.     

Etude des petits cycles—XXX : Extension de cycle generale de cyclopropanols: Halomethyl-1, hydroxymethyl-1, vinyl-1, acyl-1, cyclopropanols,et des oxaspiropentanes en cyclobutanones

Cyclopropanols 5, 6 and 2 with substituent groups (-CH₂OH, -CH₂OTs, -CH₂Br) in the 1-position, and oxaspiropentane 8, have been prepared from methylenecyclopropane. Cyclopropanols with vinyl groups in the 1-position (1-vinyl 12, 1-cyclopentenyl 13 and 1-cyclohexenyl 14) and 1-cyclopropylcyclopropanol 20 have been prepared from 1, 3-dichloroacetone.Each of the compounds readily undergoes ring expansion to the corresponding cyclobutanones. The reaction provides a simple route to cyclobutanones, the parent ketone itself being easily obtained from oxaspiropentane 8.     

The chemistry of N-benzylidene-1,4-phenylenediamine palladacycles: The crystal and molecular structure of the first tetranuclear palladacycle with bridging Ph2PCH2PPh2 ligands

The reaction of the tetranuclear halide-bridged complexes 1?2(a?d) with Ph₂PCH₂PPh₂ (dppm) or Ph₂PC(CH₂)PPh₂ (vdpp) in 1:2 molar ratio and NH₄PF₆ afforded the novel tetarnuclear palladacycles 3?6 (a, c, d) as 1:2 electrolytes with bridging diphosphine and halogen ligands. The structure of 4a has been determined by X-ray diffraction analysis, and represents the first example of a tetranuclear palladacycle with bridging dppm and halogen ligands. Reaction of 1?2(a?d) with (Ph₂PCH₂CH₂)₂PPh (triphos) in 1:2 molar ratio gave 7(a?d) bearing two pentacoordinated palladium atoms. The structure of 7a, as determined by X-ray diffraction analysis, shows the distorted square pyramidal geometry around the metal centers. Treatment of 1?2(a?d) with dppm, vdpp or Ph₂PN(Me)PPh₂ (dppma) in 1:4 molar ratio gave the dinuclear palladacycles 8?10(a?d) with a chelating diphosphine ligand at each metal center; further treatment of 9(a?c) with the nucleophiles pyrrolidine, piperidine, morpholine or 4-methyl-piperidine gave the Michael addition derivatives 11?12(a?c), 13b, 13c and 14c, promoted by the withdrawing effect of the palladacycle which activates the CCH₂ double bond.     

Studies on β methyl-1-and 3-phenyl allyl chlorides

The hydrolysis of β-methyl-1- and 3-phenylallyl chlorides (1a and 1b) have been investigated in aqueous dioxan and the proposed mechanism compared with those reported for the corresponding 1- and 3-phenylallyl chlorides (2a and 2b). Hydrolysis of 1a and 1b proceeds via the same mechanism as 2a and 2b, respectively, with different behavior by the first intermediate. The first intermediate of 1a rearranges to the corresponding conjugated compound through a transition state rather than an intermediate. Theoretical calculations on the carbonium ions of 1 and 2 using a semiempirical MINDO/3 molecular orbital method show that the charge densities on carbon atoms of 1 are nearly the same as those of 2. The main difference is in the bond angle C¹-C⁸-C⁹.     

Enamine Chemistry—XXIV.: Synthesis,thiation, and reduction of lactams

Enamines, 1, prepared from cyclohexanones or cyclopentanones are reacted with acrylamide to give lactams, the condensed 2-piperidones, 2. Ethyl 2-(1-pyrrolidinyl)-2-cyclohexene-1-propanoate, 3, when treated with primary amines, produces the corresponding N-substituted 2-piperidones, 4. Ethyl 2-(1-pyrrolidinyl)-2-cyclohexene-1-ethanoates and ethyl 2-(1-pyrrolidinyl)-2-cyclopentene-1-ethanoate, 5, react with primary amines to give condensed N-substituted 2-pyrrolidones, 6, and non-cyclic imines, 7. The starting enamines, 1, treated with 2-bromo acetamides only afford the N-alkylated compounds 8 (2-pyrrolidino acetamides), and the regioselectivity of this reaction is rationalized in terms of the HSAB-principle. Compound 1 undergoes an exchange reaction (aminolysis) when reacted with primary amines to give the imines 9. Thiation of the lactams 2 and 6 with the Lawesson reagent (LR), affords the corresponding thiolactams, 10. Reduction of the lactams and thiolactams, 2, 6, and 10 by LAH gives the imines, 11, and the enamines, 16. Further reduction of 11 (LAH) affords the saturated amines, 15. The stereochemistry for the formation of 15 is discussed using the torsion angle notation and the principal of least torsional distortion. In a one-pot reaction using LAH-acetic anhydride the lactams, 2, and the thiolactams, 10, are transformed into the enamides, 14. Compound 14 was also obtained from 11 by direct acetylation with acetic anhydride in the presence of triethylamine.     

Synthesis,properties and structural characterization of 4-(2-ammonioethyl)piperazin-1-ium tetrasulfidotungstate hemihydrate and 1-ethylpiperazinediium tetrasulfidotungstate

The reaction of ammonium tetrasulfidotungstate with 2-piperazin-1-ylethanamine or 1-ethylpiperazine results in the formation of 4-(2-ammonioethyl)piperazin-1-ium tetrasulfidotungstate hemihydrate (C₆H₁₇N₃)[WS₄]·½H₂O 1 or 1-ethylpiperazinediium tetrasulfidotungstate (C₆H₁₆N₂)[WS₄] 2. The hemihydrate 1 can be dehydrated to the anhydrous compound (C₆H₁₇N₃)[WS₄] 1a, which can be rehydrated to 1. Both 1 and 2 decompose to amorphous carbon containing tungsten disulphide. Compound 1 crystallizes in the centrosymmetric monoclinic space group C2/c, while compound 2 crystallizes in the centrosymmetric orthorhombic space group Pbca. The structures of 1 and 2 consist of a slightly distorted tetrahedral [WS₄]^2? anion and 4-(2-ammonioethyl)piperazin-1-ium (1) or 1-ethylpiperazinediium dication (2) and additionally a lattice water in 1. In the crystal structure of 1 and 2 the organic cation and the [WS₄]^2? anion are linked to each other via several weak N–H?S and C–H?S bonding interactions. The lattice water serves as a link between pairs of cations and pairs of anions with the aid of O–H?S and N–H?O interactions in compound 1.     

Octahedral bis(acetylide) and bis(diacetylide) complexes of ruthenium(II) with linear C2MC2 and C4MC4 chains: The first X-ray structures of the all trans bis(acetylides) Ru(CO)2(CCPh)2(PEt3)2 and Ru(CO)2(CCH)2(PEt3)2

Bis(acetylides) and bis(diacetylides) of ruthenium(II), trans-Ru(CO)₂(PEt₃)₂(CCR)₂ (1) (1a, R  Ph; 1b, R  ^tBu; 1c, R  SiMe₃; 1d, R  H) and trans-Ru(CO)₂(PEt₃)₂(CCC CR)₂ (2) (2a, R  SiMe₃; 2b, R  H) have been synthesized and characterised. The first single crystal X-ray analyses of these all trans-acetylides have revealed linear C₂RuC₂ chains in 1a and 1d.