bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bis(ZnII–cyclen) Complex as a Novel Receptor of Barbiturates in Aqueous Solution
Authors: Koike Tohru , Takashige Megumi , Kimura Eiichi , Fujioka Haruto , Shiro Motoo 
Published: September 2007

AbstractA new bis‐zinc(II) receptor (Zn2L), which has two macrocyclic 12‐membered tetraamine (cyclen) ZnII complexes connected through a p‐xylene bridge, has been synthesized as a novel host molecule to recognize barbiturates (such as barbital (bar)) in aqueous solution. Each of the zinc(II) ions in the biszinc(II) receptor was originally intended to match the dianionic barbital anion (bar2−) with supplementary hydrogen bonds between the cyclen NH's and the three carbonyl oxygens in complementary positions to yield a 1:1 complex, Zn2L–bar2−. From an aqueous solution of equimolar Zn2L and barbital at pH 8, however, a cyclic 2:2 complex, (Zn2L‐bar2−)2, was isolated and characterized by X‐ray crystal analysis. The NMR study in 10% (v/v) D2O/H2O has revealed dissociation of (Zn2L–bar2−)2 solely into the original target 1:1 complex Zn2L–bar2− and established the dimerization constant for 2Zn2L–bar2− → (Zn2L–bar2−)2, Kd ( = [(Zn2L–bar2−)2]/[Zn2L–bar2−]2) to be 103.4 M−1. The thermodynamic parameters were evaluated from the NMR measurements at 25, 35, 45, and 55°C: ΔG = –1.9 × 104 J mol−1, ΔH = – 3.3 × 104 J mol−1, ΔS = – 49 J mol−1 K−1 at 25°C. Potentiometric pH titration of Zn2L (1 mM) and barbital (1 mM) disclosed extremely facile deprotonation of the two imido groups of barbital at pH less than 7 to form the dianionic barbital‐bound ZnII complexes Zn2L–bar2− and (Zn2L–bar2−)2, where‐by the barbital binding affinity for Zn2L was estimated to be Kbar ( = [Zn2L–bar2−]/[uncomplexed Zn2L][uncomplexed barbital]) = 105.8 M−1 at pH 8 and 25°C with I = 0.10 (NaNO3). The significance of the bis‐zinc(II) receptor in stabilizing the dianionic barbital is evident by comparison with the interaction of ZnII–cyclen complex (ZnL) with barbital, which yields only a 1:1 monoanionic barbital complex, ZnL–bar− (Kbar = [ZnL–bar−]/[uncomplexed ZnL][uncomplexed barbital] = 104.2M−1 at pH 8 and 25°C with I = 0.10 (NaNO3)).
Self‐assembling Tetrathiafulvalene‐based Rotaxanes and Catenanes
Authors: Li Zhan‐Ting , Stein Paul C. , Becher Jan , Jensen Dorthe , Mørk Pernille , Svenstrup Niels 
Published: September 2007

AbstractA general stepwise approach is described for the preparation of tetrathiafulvalene (TTF)‐based linear and monoand dimacrocyclic compounds incorporating one or two 1,4‐dioxyphenylene, 9,10‐dioxyanthrylene, or 1,5‐ or 2,6‐dioxynaphthylene units from readily available starting materials. By utilizing the π–π stacking interactions of the TTF unit with the dipyridinium dication of 1,1′‐[1,4‐phenylenebis (methylene)] bis‐4,4′‐bipyridinium bis(hexafluorophosphate), a rotaxane and two [2]catenanes were synthesized starting from the linear and monomacrocyclic compounds, respectively. From the dioxyphenylene‐based dimacrocycle, three [3]pseudocatenanes (trans, cis, and a mixture of cis/trans isomers) were obtained with the trans compound as the major product. From the dioxyanthrylene dimacrocycle, only the trans‐[3]pseudocatenane was obtained. Catenane products were formed quantitatively from the 1,5‐dioxynaphthylene dimacrocycle in a template‐directed reaction, affording a trans‐[3]pseudo‐catenane together with a [4]pseudocatenane (mixture of cis/trans isomers). From the 2,6‐dioxynaphthylene dimacrocycle, a cis‐[3]pseudocatenane was obtained as the major product and a trans‐[3]pseudocatenane as the minor one. For the [3]pseudocatenanes (i.e., both the cis and trans catenanes), in which the TTF units were clamped by the tetracationic macrocycle, isomerizations were completely prevented even in the presence of trifluoroacetic acid. All new rotaxanes and catenanes were characterized by electrospray mass spectrometry, and the cis‐ and trans‐ [3]pseudocatenanes were additionally investigated by 1H NMR spectroscopy. The electrochemical and spectral properties of the rotaxane and the catenanes are reported. Catenane formation increases the redox potentials of the TTF unit. The results demonstrate the versatility of TTF as a building block in the construction of supramolecular structures.
Conformational Studies of Chiral Vinylogous Sulfonamidopeptides
Authors: Gennari Cesare , Salom Barbara , Potenza Donatella , Longari Chiara , Fioravanzo Elena , Carugo Oliviero , Sardone Nicola 
Published: September 2007

AbstractThe conformational preferences of chiral vinylogous aminosulfonic acids (vs‐amino acids) and of the corresponding oligomers (vs‐peptides) were investigated by a combination of X‐ray crystallography, variable‐temperature (VT) 1H NMR spectroscopy, FT‐IR spectroscopy, and NOE experiments. The major source of conformational freedom in the monomers is the rotation around the CC bond connecting the double bond with the allylic stereocenter (NC*CC). The allylic conformational preferences can be altered in the oligomers by the formation of secondary structures enforced by hydrogen bonding. Twelve‐membered‐ring hydrogen bonding is detected in the crystal structure of vs‐dipeptide 9, while fourteen‐membered‐ring hydrogen bonding is the most common folding pattern for the oligomers in chloroform solution. The experimental results are complemented by computer modeling: suitable force‐field (FF) parameters for the unsaturated sulfonamide group were developed from ab initio calculations. A Goodman–Still systematic pseudo‐Monte‐Carlo search was used for the conformational search. The conformers were minimized in chloroform with the GB/SA model. The calculations correctly predicted both the size of the hydrogen‐bonded ring and its relative importance, in agreement with the experimental data in solution.
Dimensional reduction in II‐VI materials: A2Cd3Q4 (A = K, Q = S, Se, Te; A = Rb, Q = S, Se), novel ternary low‐dimensional cadmium chalcogenides produced by incorporation of A2Q in CdQ
Authors: Axtell Enos A. , Liao Ju‐Hsiou , Pikramenou Zoe , Kanatzidis Mercouri G. 
Published: September 2007

AbstractThe synthesis of the isomorphous, layered chalcogenides K2Cd3S4 (I), Rb2Cd3S4 (II), K2Cd3Se4 (III), Rb2Cd3Se4 (IV), and K2Cd3Te4 (V) in molten A2Qx fluxes in reported (A = K, Rb; Q = S, Se, Te; x = 2 to 3). The compounds form as (Cd3Q4) layers interspersed with A + cations; the layers are composed of Cd3Q2−4 units shaped as truncated cubes. The compounds have room‐temperature band gaps of 2.75, 2.92, 2.36, 2.37, and 2.26 eV for I, II, III, IV, and V, respectively, and also display strong photoluminescence. The thermal analysis data for all compounds are reported. The properties of these compounds are compared with those of the three‐dimensional compounds CdS, CdSe, and CdTe, as well as those of the nanometer‐sized CdQ clusters. A conceptual context is presented to connect all these different types of compounds.
A bis(diimidazole)Copper Complex Possessing a Reversible CuII/CuI Couple with a High Redox Potential
Authors: McMaster Jonathan , Beddoes Roy L. , Collison David , Eardley David R. , Helliwell Madeleine , Garner C. David 
Published: September 2007

AbstractThe new diimidazole ligand, bis (1‐methyl‐4,5‐diphenylimidazol‐2‐yl)ketone (BIMDPK), has been synthesised, characterised and shown to form four‐coordinate bis(diimidazole) CuII and CuI complexes in the salts [Cu(bimdpk)2]‐[BF4]2 and [Cu(bimdpk)2][PF6], the structures of which have been determined by X‐ray crystallography. The cations of these salts have a very similar geometry with CuII–Nav = 1.949 and CuI–Nav = 1.999 Å; the N‐Cu‐N interbond angles are constrained by 1) the bite angle of the BIMDPK ligand to 94 ± 2° and 2) the interligand steric interactions, which lead to the dihedral angle of the intraligand CuN2 planes of 68.2° for CuII and 74.9° for CuI–that is, a CuN4 geometry intermediate between tetrahedral and square planar. The X‐band EPR spectrum for the powdered CuII compound is typical of an approximately D2 CuN4 centre possessing a dxy ground state (gx = 2.080, gy = 2.075, gz = 2.291; Az = 112.3 × 10−4 cm−1). The UV/vis spectra are dominated by charge‐transfer bands, and both the CuII and CuI systems are intensely coloured. The EPR and electronic spectra indicate that these cations have a very similar structure in the solid state and in solution; the potential of the [Cu(bimdpk)2]2+/[Cu(bimdpk)2]+ couple is 0.59 V vs. SCE in MeCN and 0.80 V vs. SCE in CH2Cl2, and the electron self‐exchange constant in MeCN is 1.9 × 104M−1S−1. Comparisons are made between the properties of the [Cu(bimdpk)2]2+/+ centres and related Cu centres in chemical and biological systems; the results of this study reinforce the view that a [Cu(His)4] centre should not be precluded from consideration in biological electron transport.
Pseudorotaxanes Formed Between Secondary Dialkylammonium Salts and Crown Ethers
Authors: Ashton Peter R. , Chrystal Ewan J. T. , Glink Peter T. , Menzer Stephan , Schiavo Cesare , Spencer Neil , Stoddart J. Fraser , Tasker Peter A. , White Andrew J. P. , Williams David J. 
Published: September 2007

AbstractA very simple self‐assembling system, which produces inclusion complexes with pseudorotaxane geometries, is described. The self‐assembly of eight pseudorotaxanes with a range of stoichiometries–1:1, 1:2, 2:1, and 2:2 (host:guest)–has been achieved. These pseudorotaxanes self‐assemble from readily available components–well‐known crown ethers, such as dibenzo[24]crown‐8 and bis‐p‐phenylene[34]crown‐10, and secondary dialkylammonium hexafluorophosphate salts, such as (PhCH2)2NH+2PF−6 and (nBu)2NH+2PF−6–and have been characterized not only in the solid state, but also in solution and in the “gas phase”. The pseudorotaxanes are stabilized largely by hydrogen‐bonding interactions and, in some instances, by aryl‐aryl interactions.
Self‐assembling [2]‐ and [3]Rotaxanes from Secondary Dialkylammonium Salts and Crown Ethers
Authors: Aston Peter R. , Glink Peter T. , Stoddart J. Fraser , Tasker Peter A. , White Andrew J. P. , Williams David J. 
Published: September 2007

AbstractThe self‐assembly of three new rotaxanes—two [2]rotaxanes and a [3]rotaxane—formed by a “threading followed by stoppering” approach is described. These template‐directed syntheses rely on the formation of pseudorotaxane intermediates, which self‐assemble in solution from functionalized secondary dialkylammonium hexafluorophosphate threads and macrocyclic polyether rings (either dibenzo‐[24]crown‐8 or its asymmetric constitutional isomer). The stoppers—substituted 1,2,3‐triazoles–were created by thermally allowed 1,3‐dipolar cycloadditions between azido groups, which terminate the threads, and di‐tert‐butyl acetylenedicarboxylate.
Novel Sulfur‐Containing Inorganic Aprotic Superacids as Effective Initiators of Low‐Temperature Cracking and Isomerization of Alkanes
Authors: Akhrem Irena , Gudima Svetlana , Vol'pin Mark 
Published: September 2007

AbstractA novel family of inorganic aprotic superacids has been found. Oxochlorides and chloride of sulfur combined with aluminium halides (SOCl2·n AlX3, SO2Cl2·n AlX3, MeSO2Cl·n AlX3, CF3SO2Cl·n AlX3, S2Cl2·n AlX3; n = 2 or 3, X = Br or Cl) are found to be effective promoters for the cracking and isomerization of alkanes at room temperature.
Dynamic Behavior in Solution of the Trans‐Hydridodihydrogen Complex [OsHCl(n2‐H2)(CO)(PiPr3)2]: Ab Initio and NMR Studies
Authors: Bakhmutov Vladimir I. , Bertrán Juan , Esteruelas Miguel A. , Lledós Agustí , Maseras Feliu , Modrego Javier , Oro Luis A. , Sola Eduardo 
Published: September 2007

AbstractReaction of complex [OsHCl‐(CO)(PiPr3)2] (1) with hydrogen gives the trans‐hydridodihydrogen complex [OsH‐Cl(n2‐H2)(CO)(PiPr3)2] (2). The H‐H distance in the dihydrogen ligand, determined by variable‐temperature 1H T1 measurements, is 0.8 Å. The fast‐spinning nature of the dihydrogen ligand of 2 has been deduced by evaluating the deuterium quadrupole coupling constant for the n2‐D2 ligand of [OsDCl(n2‐D2)(CO)(PiPr3)2] ([D3]2). Measurements of the equilibrium constants for formation of 2 (K) give ΔH0 = – 14.1 ± 0.5 kcal mol−1 and ΔS0 = – 30 ±1 e.u. An equilibrium isotope effect Kd/K of 2.8 is found for this reaction. The activation parameters for the H2 loss from 2 are ΔH‡ = 14.6 ± 0.2 kcal mol−1 and ΔS‡ = 9.9 ± 0.5 e.u. Hydrogen exchange between the hydrido and n2‐H2 ligands of 2 takes place at a slow rate (kobs2) at high temperatures. Activation parameters ΔH‡ = 17.4 ± 0.5 kcal mol−1 and ΔS‡ = 1.3 ± 1 e.u., and a kinetic isotope effect (kobs2/kobs2d) of 4.6 at 333 K have been determined for this exchange. Ab initio calculations on the model system [OsH‐Cl(H2)(CO)(PH3)2] confirm that the trans‐hydridodihydrogen complex [OsH‐Cl(n2‐H2)(CO)(PH3)2] (4) is the most stable species (rHH = 0.84 Å). In addition, a cis‐hydridodihydrogen complex 5, with a relative energy of 13.8 kcal mol−1, occupies a local minimum in the potential hypersurface. The energy of other possible trihydrido isomers have also been evaluated. On the basis of the thermodynamic and kinetic data, and the results of the ab initio calculations, the possible mechanism for the H/n2‐H2 exchange is discussed.
The β‐Lactone Route to a Totally Stereoselective Synthesis of Carnitine Derivatives
Authors: Bernabei Ida , Castagnani Roberto , Angelis Francesco De , Fusco Enrico De , Giannessi Fabio , Misiti Domenico , Muck Sandra , Scafetta Nazareno , Tinti Maria Ornella 
Published: September 2007

AbstractThe syntheses of the enantiomerically pure, carnitine‐related β‐lactones 10 and 12 starting from various carnitine precursors of opposite configuration (or carnitine itself) are described. (R)‐3‐Chlorocarnitine (20) has also been directly prepared from (S)‐carnitine (14) and has been cyclized to 12 by a second inversion of configuration of the stereogenic centre. By nucleophilic attack at the carbonyl carbon, the β‐lactone carnitine derivatives have been converted into esters, amides and guanidino congeners. Following this route, it is possible to obtain the biologically active isomer (R)‐carnitine (1) starting from the otherwise useless industrial by‐product (S)‐carnitine (14). Nucleophilic attack by selected ambidient nucleophiles at the β‐carbon of the same β‐lactone derivatives results in a second inversion of configuration of the stereogenic centre. Besides aminocarnitine (3), chiral acetylcarnitine (2) and acetylthiocarnitine (5) have been synthesized in homochiral forms following this latter procedure.
Nanometre‐Scale Molecular Ribbons
Authors: Breidenbach Stefan , Ohren Stefan , Vögtle Fritz 
Published: September 2007

AbstractThe longest molecular ribbons known to date (3–10), composed of a series of [3.3]metacyclophane units, have been synthesised by means of a repetitive synthetic strategy. These multiple ring systems with up to nine bridged benzene rings in a row are the longest structurally perfect cyclophane sequences known to date. The synthetic strategy comprises three steps: ester reduction to a tetrakis(hydroxymethyl) compound, derivatisation to the corresponding tetrakis(bromomethyl) derivative, and double cyclisation with the new key building block 14, which was especially developed for this sequence. Single‐crystal X‐ray analyses (3 a–7 a) and 1H NMR spectroscopy (3–10) show that, regardless of their length, these molecules adopt zigzag folded all‐syn conformations. π‐Stacks of nanometre dimensions are thus formed.
Conformation and Self‐Association of a Hybrid Peptide of Cecropin A and Melittin with Improved Antibiotic Activity
Authors: Fernández Imma , Ubach Josep , Fuxreiter Monika , Andreu José Manuel , Andreu David , Pons Miquel 
Published: September 2007

AbstractA 15‐residue hybrid peptide containing residues 1–7 from cecropin A and residues 2–9 from melittin, CA‐(1–7)M(2–9), is a potent antibiotic with broader activity than cecropin A, but without the cytotoxic character of melittin. The conformational behaviour of CA(1–7)M(2–9) including the formation of multimeric species in solution has been investigated by circular dichroism, ultracentrifugation, electrospray mass spectrometry, NMR and energy calculations. Addition of hexafluoroisopropanol or liposomes causes the appearance of a CD spectrum characteristic of a helical structure that changes with pH, buffer and peptide concentration. The concentration dependence is atypical, as the ellipticity at 222 nm decreases with peptide concentration and is not correlated with a corresponding decrease in helix content as measured from the NMR spectra. The presence of aggregated structures is demonstrated by ultracentrifugation and ES‐MS experiments, which also provide an indication of the stoichiometry. Longrange NOEs suggest a model of aggregation with neighbouring molecules packed antiparallel. Aggregation causes very slow proton‐deuterium exchange in some amide protons in the C‐terminal region and provides a method for estimating a very large association constant (ca. 106M−1) as well as the stoichiometry of the aggregates. The tendency to aggregate seems to be an inherited feature from melittin and may enhance the antibiotic activity either by facilitating the incorporation of the peptide into the membrane in large quantities or by promoting the disruption of the membrane.
Synthesis of 4‐Silylcyclobut‐2‐enethiones and their Use in Cyclobutadiene Generation
Authors: Müller Martin , Förster Wolf‐Rüdiger , Holst Andreas , Kingma Arend J. , Schaumann Ernst , Adiwidjaja Gunadi 
Published: September 2007

AbstractAlkynyl silyl sulfides 2 reacted with ynamines 3 to give 1:1 adducts. The structure of 4‐silylcyclobut‐2‐enethiones 4 was confirmed by X‐ray analysis of 4a. A cyclobutadiene intermediate is probably not involved in this reaction; we think that it is initiated by a silyl transfer from 2 to 3, and that this is followed by a combination of the resulting ions to give the unsaturated thioketene 7, which undergoes an electrocyclization to give products 4. In the reaction of thiones 4 with trimethyloxonium tetrafluoroborate (Meerwein salt) selective methylation at sulfur was observed to give cyclobutenethionium ions 16. Ions 16 underwent fluoride‐induced desilylation with various fluoride sources to give cyclobutadienes 17, which could not be isolated, but trapping of 17 a‐c was possible with dimethyl acetylenedicarboxylate yielding regioisomeric benzene derivatives 20–23. Similarly, 17 a and bis(methylthio)methylene malononitrile (24) led to hexatriene derivative 27 by a sequence of cycloaddition and two ring‐opening reactions. In contrast, silyl‐substituted cyclobutadienes 17d,e dimerized even in the presence of trapping agents to anti‐tricyclo‐[4.2.0.02,5]octadienes 29; this suggests that a two‐step cycloaddition is taking place, rather than a concerted Diels‐Alder reaction. Attempts to intercept 17d, e, generated from 16d,e with cyclopentadiene (30), gave deprotonation of 30 leading to substitution of the methylthio group in 16 and finally to formation of cyclobutenes 33 through a hydrogen shift.
Effects of Nitrogen Substitution in Poly(Pyrazolyl)Borato Ligands: From Orbital Energy Levels to C–H ⃛ O Hydrogen Bonding
Authors: Janiak Christoph , Scharmann Tobias G. , Green Jennifer C. , Parkin Richard P. G. , Kolm Mario J. , Riedel Erwin , Mickler Wulfhard , Elguero José , Charamunt Rosa M. , Sanz Dionisia 
Published: September 2007

AbstractThe electronic effect of substituting CH with N in poly(pyrazolyl)‐borato ligands and their transition‐metal complexes is shown to be a decrease in energy of the filled metal and ligand orbitals. This conclusion is based on the cyclovoltammograms and photoelectron spectra of bis(hydrotris(azolyl)borato)‐iron(II) and ‐cobalt(II) complexes (azolyl = pyrazolyl and 1,2,4‐triazolyl) and on MO calculations. 57Fe Mössbauer spectra of bis(hydrotris(1,2,4‐triazolyl)‐borato)iron(II) show that there is a fine‐tuning of the HOMO–LUMO gap by a shift in transition temperature for the spin equilibrium. 15N NMR spectroscopy supports the assignment of a higher negative charge to the exodentate N‐4 nitrogen than to the endodentate N‐2 or N‐3 positions in the poly(azolyl)borato anions, where azolyl is 1,2,4‐triazolyl or tetrazolyl. The electron withdrawing effect of the additional nitrogen atoms and the in‐corporation of water of crystallization by O–H ⃛ N bonding both assist in the formation of (azolyl)C–H ⃛ O bonds.
Photoreactions of Phenyl‐Substituted N‐(pent‐4‐enyl‐1‐oxy)Pyridine‐2(1 H)‐Thiones
Authors: Hartung Jens , Hiller Margit , Schmidt Philipp 
Published: September 2007

AbstractA series of hitherto unknown N‐(pent‐4‐enyl‐1‐oxy)pyridine‐2(1 H)‐thiones (6) were prepared from substituted pent‐4‐enyl tosylates or benzylic chlorides. On irradiation with incandescent light heterocycles 6 liberated alkoxy radicals 2, which were studied for rearrangement reactions. Surprisingly, all transformations involving the 1‐phenylpent‐4‐enyl‐1‐oxy radical (2a), for example, to give the substituted thioether 8, 2‐bro‐momethyl‐5‐phenyltetrahydrofuran (11), or the tetrahydrofuran 14a, were not stereoselective. On the other hand 2‐, 3‐ mono‐, and 1,5‐disubstituted pent‐4‐enyl‐1‐oxy radicals 2d‐e and 2g cyclized in good yields and with good to excellent stereoselectivities to give the corresponding 2,4‐cis‐ and 2,3‐trans‐phenyltetra‐hydrofurfuryl radicals 3d‐e, and the trans‐2‐benzyl‐5‐methyl substituted intermediate 3g. The major reaction mode of the 4‐phenylpent‐4‐enyl‐1‐oxy radical (2f) was the 6‐endo cyclization, which afforded 3‐phenyltetrahydropyran (13f) as the major product (endo:exo = 93:7) after trapping with hydrogen donors. According to the experimental data of the present study, the unusual reactivity of the 1‐phenylpent‐4‐enyl‐1‐oxy radical (2a) in 5‐exo–trig ring closures could be caused by a coplanar arrangement of the benzyloxy moiety in the transition state of the cyclization. This interaction would lock the radical center in 2a in a preferred conformation, which would result in similar steric effects for both cis‐ and trans‐ cyclizations.
Reactions of the Double‐Stranded Oligonucleotide d(TTGGCCAA)2withcis‐[Pt(NH3)2(H2O)2]2+and [Pt(NH3)3(H2O)]2+
Authors: Reeder Franziska , Gonnet Florence , Kozelka Jiří , Chottard Jean‐Claude 
Published: September 2007

AbstractThe kinetics of the reactions between the GG‐containing double‐stranded oligonucleotide d(TTGGCCAA)2(II) and the platinum complexescis‐[Pt‐(NH3)2(H2O)2]2+(1) and [Pt(NH3)3‐(H2O)]2+(2) were studied and compared with those already determined for the reactions of the single‐stranded octanucleotide d(CTGGCTCA) (I).[1]The results were as follows: i) Complex1reacted faster than2with bothIandII. ii) Both complexes1and2reacted faster withIIthan withI. This acceleration was greater for1(x 13) than for2(x4) and only due to the increase of the platination rate of the 5′‐G of the GG sequence. iii) For bothIandII, the first platination by1and2was faster on the 5′‐G than on the 3′‐G. This difference was more significant for the platination ofII(k5′/k3′= 12 for1and 5 for2) than ofI(k5′/k3′≤ 2). iv) The cyclization reaction of the monoadducts (G*) of1to yield the GGcis‐Pt(NH3)2+2chelate (G*G*) was considerably slowed down in the duplex. This rate decrease was significantly larger for the chelation of the 5′‐G*(factor of 16) than of the 3′‐G*(factor of 4) monoadducts. v) The intrastrand chelation of the 3′‐G*monoadducts (k3′c) was faster than that of the 5′‐G*monoadducts (k5′c), both forIandII(k3′c/k5′c= 3 and 13, respectively). vi) In addition to the intrastrand G*G*crosslink, we also observed the interstrand crosslink d(GG*CC)–d(GG*CC) between the two 3′‐Gs of the central tetranucleotide. The rate constant for the interstrand crosslinking (k3′i) was half that of the intrastrand chelation (k3′c). vii) The 5′ monoadduct, which was formed faster (k5′<k3′) and was chelated more slowly (k5′c>k3′i<k3′c), exhibited a half‐life of 3.2 h under our experimental conditions.