bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of non‐planarity on the spin distribution in the radical anions containing the stilbene or the azobenzene π‐system: An ESR and ENDOR Study
Authors: Gerson Fabian , Lamprecht Axel , Scholz Markus , Troxler Heinz , Lenoir Dieter 
Published: December 2004

AbstractThe radical anions of 5H‐dibenzo[a,d]cycloheptene (9), 5 H‐dibenzo[c,f][1,2]diazepine (10), 5,6‐dihydrodibenzo[a,e]cyclooctene (11), 5,6‐dihydrodibenzo[c,g][1,2]diazocine (12), and (E)‐2,2,5,5‐tetramethyl‐3,4‐diphenylhex‐3‐ene (13) were characterized by ESR and ENDOR spectroscopy. Their hyperfine data were compared with those previously reported for radical anions also containing the stilbene or the azobenzene π‐system. Whereas the π‐spin distribution in the radical anions of the stilbene series is only moderately sensitive to deviations of the π‐system from planarity, the radical anions of the azobenzene series respond to steric strain by shifting the π‐spin population from the benzene rings to the azo group. This finding is impressively demonstrated by the similar hyperfine data for 9· − and 11· − which contrast with the strongly highly hindered 13· −. A. plausible interpretation is readily provided by the electron affinities of the constituent π‐moieties in stilbene and azobenzene. While those of benzene and ethene are both comparatively low, the azo group has a considerably higher electron affinity.
Model Studies Towards a Novel Fragment Coupling for the Synthesis of Mycalamides and Related Natural Products
Authors: Hoffmann Reinhard W. , Breitfelder Steffen , Schlapbach Achim 
Published: December 2004

AbstractThe mycalamides (3) and related natural products contain an α‐hydroxy acid 1 bound via an amide bond to an α‐alkoxy amine. The high density of functional groups in the ‘coupling region’ renders the coupling reactions delicate. Model studies showed that an alternate assembly of the molecular halves is possible using an ‘Umpolung’ of an α‐alkoxy isocyanate, e.g. 13. Thus, combination of the ester 12 with 13 led to the α‐keto amide 16. The further elaboration of 16 to the α‐hydroxy‐amide structure found in the mycalamides is reported.
Corniculoside, a New Biosidic Ester Secoiridoid from Halenia corniculata
Authors: Rodriguez Sylvain , Wolfender Jean‐Luc , Hostettmann Kurt , Odontuya Gendaramyn , Purev Ondognii 
Published: December 2004

AbstractChemical screening of the secondary metabolites from Halenia corniculata L. (CORNAZ), by LC/UV,LC/TSP‐MS (thermospray), and LC/ES‐MS (electrospray) was used for the targeted isolation of corniculoside (1), a new biosidic ester secoiridoid. The structure was established as 7‐β‐[(E)‐4′‐O‐(β‐D‐glucopyranosyl)caffeoyloxy]‐sweroside by 1D‐ and 2D‐NMR, LC/UV, LC/MS, and FAB‐MS data, in combination with chemical reactions.
Diazoaldehyde Chemistry. Part 3. Synthesis of 4‐acyl‐1H‐1,2,3‐triazole derivatives
Authors: Sezer Özkan , Dabak Kadir , Akar Ahmet , Anaç Olcay 
Published: December 2004

AbstractTen new α‐diazo‐β‐oxoaldehydes were condensed with aniline, ammonia, hydroxylamine, and semicarbazide to yield new 4‐acyl‐(1‐substituted)‐1H‐1,2,3‐triazoles in moderate‐to‐good yields. The method is simple and regiospecific. The latter feature makes this method superior to the widely used acylacetylene + azide approach.
N7‐DNA: Synthesis and Base Pairing of Oligonucleotides Containing N7‐(2‐Deoxy‐β‐D‐erythro‐pentofuranosyl)guanine (N7Gd)
Authors: Seela Frank , Leonard Peter 
Published: December 2004

AbstractThe synthesis of oligonucleotides containing N7‐(2‐deoxy‐β‐D‐erythro‐pentofuranosyl)guanine (N7Gd; 1) is described. Compound 1 was prepared by nucleobase‐anion glycosylation of 2‐amino‐6‐methoxypurine (5) with 2‐deoxy‐3,5‐di‐O‐(4‐toluoyl)‐α‐D‐erythro‐pentofuranosyl chloride (6) followed by detoluoylation and displacement of the MeO group (8→10→1). Upon base protection with the (dimethylamino)methylidene residue (→11) the 4,4‐dimethoxytrityl group was introduced at OHC(5′) (→12). The phosphonate 3 and the phosphoramidite 4 were prepared and used in solid‐phase oligonucleotide synthesis. The self‐complementary dodecamer d(N7GC)6 shows sigmoidal melting. The Tm of the duplex is 40°. This demonstrates that guanine residues linked via N(7) of purine to the phosphodiester backbone are able to undergo base pairing with cytosine.
Synthesis of 4‐Substituted 1H‐Benzimidazole 2′‐Deoxyribonucleosides and Utility of the 4‐Nitro Compound as Universal Base
Authors: Seela Frank , Bourgeois Werner , Rosemeyer Helmut , Wenzel Thomas 
Published: December 2004

AbstractThe stereoselective synthesis of 4‐substituted 1H‐benzimidazole 2′‐deoxyribonucleosides is described. Regioisomeric (N1 and N3) β‐D‐deoxyribonucleosides 2a–c and 3a–c were formed. 13C‐NMR Chemical shifts of the 1H‐benzimidazole 2′‐deoxy‐β‐D‐ribofuranosides were correlated with point charges of C‐atoms as well as with Hammett constants of the exocyclic substituents. Phosphonate and phosphoramidite building blocks of 4‐nitro‐1H‐benzimidazole 2′‐deoxyribofuranoside (2a) were prepared (see 4a, b). Oligonucleotides of the d(A20) type were synthesized in which the two central dA bases were replaced by 4‐nitro‐1H‐benzimidazole residues. They were hybridized with oligomeric dT and related oligomers having the other conventional bases opposite to the 4‐nitro‐1H‐benzimidazole moieties. Within these duplexes (12·13, 12·14, 12·15, and 12·16), the destabilization was almost independent of the mismatch which is required for a universal base. The thermodynamic data indicate that the 4‐nitro‐1H‐benzimidazole residues do not form H‐bonds with opposite bases but are stabilizing the duplex by stacking interactions and favorable entropic changes.
Studied Directed toward the Synthesis of Phomenoic Acid. Part 2. Stereocontrolled Synthesis of the C(7)‐to‐C(14) Segment
Authors: Hassan Hammed H. A. M. , Tamm Christoph 
Published: December 2004

AbstractStarting from the esters (2E,4S)‐6 and (2E,4R)‐6, bromo aldehydes (S)‐9 and (R)‐9 as well as bromo alcohols (S)‐10 and (R)‐10, respectively, were prepared. Bromo alcohol (R)‐8 was converted to the diol (2E,4R)‐16. Ozonolysis of the latter led to aldehyde (R)‐17, which was transformed, by a Wittig reaction, to (2R,4E,6R)‐18, corresponding to the C(7)‐to‐C(14) segment of phomenoic acid (1). Attempts to improve the yields by applying a Julia coupling of (R)‐23, which was prepared from (2E,4R)‐7, with (R)‐24 were unsuccessful. Finally, the coupling of the iodo derivative (2E,4S)‐28 with the lithiated derivative of 1,3‐dithiane 30 by the Corey‐Seebach ‘Umpolung’ led to (3S,4E)‐32 which is a derivative of the C(7)‐to‐C(14) segment of 1, suitable for further transformations.
Synthese der p‐Cumaroylspermidine
Authors: Hu Wenqing , Hesse Manfred 
Published: December 2004

The Synthesis of p‐CumaroylspermidinesThe synthesis of three mono[(E)‐3‐(4‐hydroxyphenyl)prop‐2‐enoyl]spermidines, 10, 20, and 28, three bis[(E)‐3‐(4‐hydroxyphenyl)prop‐2‐enoyl]spermidines, 6, 16, and 25, and one tris[(E)‐3‐(4‐hydroxyphenyl)prop‐2‐enoyl]‐spermidine is described.
Nucleosides. Part LX. Synthesis and Characterization of Monomeric Cordycepin‐Vitamin and Cordycepin‐Lipid Conjugates Model Substances for Biodegradable Ester and Carbonate Linkages in Conjugates and Potential Inhibitors of HIV‐1 Replication
Authors: Wasner Marita , Pfleiderer Wolfgang , Suhadolnik Robert J. , Horvath Susan E. , Kon Ning , Guan Ming‐Xu , Henderson Earl E. , Suhadolnik Robert J. , Henderson Earl E. , Adelson Martin E. 
Published: December 2004

AbstractMonomeric 3′‐deoxyadenosine (cordycepin) was modified at the 2′‐O‐ (13–18) and 5′‐O‐position (25–29) by the vitamins E, D2, and A and by the two lipids 1,2‐di‐O‐palmitoylglycerol and 1,2‐di‐O‐hexadecylglycerol via succinate or carbonate linkages. The base‐labile conjugates afforded protection groups like the 2‐(4‐nitro‐phenyl)ethoxycarbonyl (npeoc) and monomethoxytrityl group (MeOTr) that are cleavable without harming the ester and carbonate bonds, respectively. Monomeric conjugates of cordycepin and vitamin E, vitamin D2, 1,2‐di‐O‐palmitoylglycerol, and 1,2‐di‐O‐hexadecylglycerol (see 13, 14, 17, 18, 25, 26, 28, and 29) inhibited HIV‐1‐induced syncytia formation 1.7 to 6.2 fold compared to 1.5‐fold for cordycepin (see Table); IC50 values for 25 and 28 were 257 and 267 m̈M, respectively. In addition, the monomeric cordycepin‐vitamin and ‐lipid conjugates inhibited HIV‐1 RT activity 28–49% which compares with a 13% inhibition of HIV‐1 RT observed for cordycepin. The minimal inhibition of HIV‐1‐induced syncytia formation and HIV‐1 RT activity did not proceed by the activation of RNase L. The monomeric conjugates tested (13, 14) increased PKR expression.
Syntheses of New Isocephems and Isodethiaoxacephems as Antimicrobial Agents
Authors: Hakimelahi Gholam H. , Hwu Jih Ru , Tsay Shwu‐Chen , Ramezani Zahra , Hwu Jih Ru 
Published: December 2004

AbstractThe cis‐configurated isocephem 26 as well as isodethiaoxacephems 21 and 33 were synthesized (Schemes 4 and 5). The key step involves chlorination of the corresponding carbanions of 23, 18, and 31 with CF3SO2Cl followed by internal alkylation. β‐Lactams 3, 21, 26, and 33 were found to possess biological activity against several pathogenic microorganisms in vitro. Electronic activation of the lactam moiety in isodethiaoxacephem 33 remarkably enhanced its biological activity.
Struktur des Zwischenproduktes einer (i‐PrO)2 TiMe2‐Methylierung: NMR‐Untersuchungen und Konformationsanalyse
Authors: Hollenstein Sandro , Hesse Manfred 
Published: December 2004

Structure of the Intermediate of a Methylation with (i‐PrO)2TiMe2: NMR Investigations and Conformational AnalysisThe intermediate of the reaction of 3‐(1‐nitro‐2‐oxocyclohexyl)propanal ((±)‐1) with (i‐PrO)2TiMe2 was shown to be a titanium salt of 6‐(hydroxynitroryl)decano‐9‐lactone. 1H‐, 13C‐, HSQC‐, 1H,1H‐TOCSY‐ and long‐range HMBC‐NMR spectra of this intermediate indicate a complexation of the carbonyl O‐atom and an O‐atom of the hydroxynitroryl group to the same Ti‐atom. The product of the reaction (t‐3‐methyl‐c‐6‐nitro‐2‐oxabicyclo[4.4.0]decan‐r‐1‐ol, (±)‐2) was reacted with several titanium reagents to give also titanium salts of the 6‐(hydroxynitroryl)decano‐9‐lactone. Monte Carlo studies and MM3* force‐field calculations of the anion of 6‐(hydroxynitroryl)decano‐9‐lactone, 3′, resulted in a conformation of the ten‐membered ring (only 9.57 kJ/mol higher in energy than the global minimum), which allows the Ti‐atom to coordinate to the O‐atom of the N(O)OH and CO group at the same time. With the suggested structure of 3′ · TiRn, we are able to explain the selectivity of the reaction.
Synthesis of Oncinotin‐11‐one, a Macrocyclic Polyamine Alkaloid from Oncinotis tenuiloba
Authors: Doll Martin K.‐H. , Guggisberg Armin , Hesse Manfred 
Published: December 2004

AbstractThis paper presents a short synthesis of oncinotin‐11‐one (11), a minor alkaloid of Oncinotis tenuiloba (Apocynaceae). Based on a disconnection approach, the spermidine portion of the key intermediate 6 was constructed consecutively by simple N‐alkylations starting from ethyl piperidine‐2‐carboxylate (1). Treatment of 6 with in situ lithiated 2‐[(10‐bromodecyl)oxy]tetrahydropyran resulted in the formation of the keto moiety under simultanous deprotection of the lactam N‐atom to give the amino ketone 7 in 71% yield. Cleavage of the tetrahydro‐2H‐pyran‐2‐yl(Thp) portion and Jones oxidation of the resulting alcohol 8 gave the amino acid 9 which was cyclized. Final N‐debenzylation of 10 provided the natural alkaloid 11. Only two protective groups were needed in this synthesis. The reaction of N‐alkyl‐lactams with organometallic reagents is discussed.
A New Approach to the Synthesis of Long‐Chain Polypropionates Based on the Diels‐Alder Monoadditions of 2,2′‐Ethylidenebis[3,5‐dimethylfuran]
Authors: Ancerewicz Jacek , Vogel Pierre 
Published: December 2004

AbstractAcidic condensation of 2,4‐dimethylfuran with acetaldehyde provided 2,2′‐ethylidenebis[3,5‐dimethylfuran] (7) which added 1 equiv. of methyl bromopropynoate to give a major adduct 8. Regio‐ and stereoselective hydroboration of the latter 7‐oxanorbornadiene derivative followed by alcohol protection and methanolysis of its β‐bromoacrylate moiety gave (1RS,2RS,4RS,5SR,6SR,1′RS)‐methyl 4‐[1′‐(3″,5″‐dimethylfuran‐2″‐yl)ethyl]‐3,3‐dimethoxy‐6‐exo‐[(2‐methoxy)ethoxy]‐1,5‐endo‐dimethyl‐7‐oxabicyclo[2.2.1]heptane‐2‐endo‐carboxylate (24) (Schemes 2 and 3). Reduction of 24 with LiAlH4, followed by H2O and MeOH elimination gave the 3‐methyl‐idene‐7‐oxanorbornan‐2‐one derivative 26 which underwent 7‐oxa ring opening through a SN2′ type of reaction with Me2CuLi (Scheme 4). Stereoselective hydrogenation and ketone reduction provided (1RS, 2SR,3RS,4RS,5RS,6RS,1′SR)‐1‐ [1″‐(3 ″,5″‐dimethylfuran‐2″‐yl)]‐c‐3‐ethyl‐c‐5‐[(2‐methoxyethoxy)m e‐c‐ethyl‐c‐c‐5‐(2‐methoxyethoxy)methoxy]‐t‐4,t‐6‐dimethyl‐cyclohexane‐r‐1,c‐2‐diol (32), the oxidative cleavage of which with Pb(OAc)4 generated a 6‐oxo‐aldehyde 33 (Schemes 4 and 5). Chemoselective protection of 33 and chemo‐ and stereoselective reductions generated (2RS,3RS,4SR,5SR,6SR,7RS)‐7‐(3′,5″‐dimethylfuran‐2′‐yl)‐2‐ethyl‐6‐hydroxy‐4‐[(2‐methoxyethoxy)methoxy]‐3,5‐dimethyloct‐1‐yl pivaloate (36) and its 4‐hydroxy 6‐epimer 40 (12 and 13 steps, resp., from adduct 8; Scheme 5). Oxidation of the furan ring of 36 led to a (2RS,3SR,4RS,5SR,6RS,7RS)‐7‐ethyl‐3,5,8‐trihydroxy‐2,4,6‐trimethyl‐octanoic acid derivative 44, a polypropionate fragment with six contiguous stereogenic centres (Scheme 6).
2‐Alkynylcyclopent‐2‐enols from 2‐Alkynylcyclohex‐2‐enones via 1‐Alkynyl‐7‐oxabicyclo[4.1.0]heptan‐2‐ones
Authors: Sander Birgit , Andresen Sven , Reichow Stefan , Dubois Katia , Agosta William C. , Margaretha Paul 
Published: December 2004

Abstract2‐Alkynylcyclohex‐2‐enones 1a–c and 2a–c react with H2O2/NaOH in MeOH to afford 1‐alkynyl‐7‐oxabicyclo[4.1.0]heptan‐2‐ones 3a–c and 4a–c, respectively. The 3‐unsubstituted bicyclic epoxy ketones 3a, 3b, and 4a, 4b react further with H2O2/NaOH, undergoing ring contraction and (formal) decarbonylation to give 2‐alkynylcy‐clopent‐2‐enols 5a, 5b, and 6a, 6b, respectively. Epoxy ketones 3 are also obtained under neutral conditions on irradiation (λ = 350 nm) of cyclohexenones 1 in air‐saturated benzene solution. Similarly, under neutral conditions oxo‐cycloalkenecarbonitriles 8 react (thermally) with H2O2 in MeCN to give the oxabicyclic carbonitriles 9.
Xylose‐DNA Containing the Four Natural Bases
Authors: Seela Frank , Heckel Maximilian , Rosemeyer Helmut 
Published: December 2004

AbstractOligonucleotides containing (2′‐deoxy‐β‐D‐xylofuranosyl)guanine have been prepared. For this purpose 2‐aminoadenosine (5) was synthesized and converted to 2′‐deoxy‐β‐D‐xyloguanosine (1). The related 2′‐deoxy‐β‐D‐xyloisoguanosine (3) and 2′‐deoxy‐β‐D‐xyloxanthosine (4) were also synthesized. Compound 1 was converted to the phosphonate and phosphoramidite building blocks 10 and 11, respectively. The oligodeoxynucleotide (5′‐3′)d(xG‐xT‐xA‐xG‐xA‐xA‐xT‐xT‐xC‐xT‐xA‐xC‐T) (18) formed a duplex with the same Tm as the parent (5′‐3′)‐(G‐T‐A‐G‐A‐A‐T‐T‐C‐T‐A‐C) (19), but with an inverted CD spectrum.
Synthesis of 2′‐Deoxy‐5‐(isothiazol‐5‐yl)uridine and Its Interaction with the HSV‐1 Thymidine Kinase
Authors: Luyten Ingrid , Winter Hans De , Busson Roger , Lescrinier Theo , Creuven Isabelle , Durant Françlois , Balzarini Jan , De Clercq Erik , Herdewijn Piet 
Published: December 2004

Abstract2′‐Deoxy‐5‐(isothiazol‐5‐yl)uridine (12) was synthesized starting from 2′‐deoxy‐5‐iodouridine using a Pd‐catalysed cross‐coupling reaction with propiolaldehyde diethyl acetal followed by deprotection and ring closure using thiosulfate. 2′‐Deoxyuridine 12 has a particular place among the 5‐heteroaryl‐substituted 2′‐deoxyuridines in that it has a high affinity for herpes simplex virus type 1 (HSV‐1)‐encoded thymidine kinase (TK) without antiviral activity. Biochemical studies revealed that 12 is a substrate for viral TK. We further investigated the interaction of 12 with the HSV‐1 thymidine kinase. The conformation of 12 in solution was established by NMR spectroscopy. The most stable conformer 12A has the S‐atom of the isothiazole ring placed in the neighbourhood of the C(4)O group of the pyrimidine moiety. The compound was docked in its most stable conformation in the active site of HSV‐1 TK and subjected to energy minimization. This demonstrated that the isothiazole moiety binds in a cavity lined by the side chains of Tyr‐132, Arg‐163, Ala‐167, and Ala‐168 and that the C(3) atom of the isothiazole moiety is located in close proximity of the phenolic O‐atom of Tyr‐132 and the aliphatic part of the Arg‐163 side chain.
The Deoxygenation and Isomerization of Artemisinin and Artemether and Their Relevance to Antimalarial Action
Authors: Jefford Charles W. , Vicente Maria G. H. , Jacquier Yvan , Favarger France , Mareda Jiri , Millasson‐Schmidt Patricia , Brunner Gerhard , Burger Ulrich 
Published: December 2004

AbstractThe treatment of artemisinin (1) and β‐artemether (6) with Zn dissolving in AcOH for a few hours results in mono‐deoxygenation giving deoxyartemisinin (5) and deoxy‐β‐artemether (7), respectively, as the sole product. In contrast, submission of 1 to FeCl2 · 4 H2O in MeCN at room temperature for 15 min causes only isomerization, (3aS,4R,6aS,7R,10S,10aR)‐octahydro‐4,7‐dimethyl‐8‐oxo‐2H‐10H‐furo[3,2‐i] benzopyran‐10‐yl acetate (8) and (3R)‐3‐hydroxydeoxyartemisinin (9) being produced in 78 and 17% yield, respectively. The action of FeCl2 · 4 H2O in MeCN on 6 is similar. Under the same conditions, 6 gives products analogous to 8 and 9 accompanied by an epimeric mixture of 2‐[4‐methyl‐2‐oxo‐3‐(3‐oxobutyl)cyclohexyl]propanaldehyde in yields of 32, 23, and 16%, respectively. No epoxide is formed on repeating the last two experiments in the presence of cyclohexene. The deoxygenation of 1 and 6 by Zn is rationalized in terms of its oxophilic nature. The catalyzed isomerization of 1 and 6 by Fe2+ is attributed to the redox properties of the Fe2+/Fe3+ system.
C‐Glycoside Analogues of N4‐(2‐Acetamido‐2‐deoxy‐β‐D‐glucopyranosyl)‐L‐asparagine: Synthesis and conformational analysis of a cyclic C‐glycopeptide
Authors: Hoffmann Matthias , Burkhart Fred , Hessler Gerhard , Kessler Horst 
Published: December 2004

AbstractThe synthesis of C‐glycosidic analogues 15–22 of N4‐(2‐acetamido‐2‐deoxy‐β‐D‐glucopyranosyl)‐L‐asparagine (Asn(N4GlcNAc)) possessing a reversed amide bond as an isosteric replacement of the N‐glycosidic linkage is presented. The peptide cyclo(‐D‐Pro‐Phe‐Ala‐CGaa‐Phe‐Phe‐) (CGaa = C‐glycosylated amino acid; 24) was prepared to demonstrate that 3‐[(3‐acetamido‐2,6‐anhydro‐4,5,7‐tri‐O‐benzyl‐3‐deoxy‐β‐D‐glycero‐D‐guloheptonoyl)amino]‐2‐[(9H‐fluoren‐9‐yloxycarbonyl)amino]propanoic acid (22) can be used in solid‐phase peptide synthesis. The conformation of 24 was determined by NMR and molecular‐dynamics (MD) techniques. Evidence is provided that the CGaa side chain interacts with the peptide backbone. The different C‐glycosylated amino acids 15–21 were prepared by coupling 3‐acetamido‐2,6‐anhydro‐4,5,7‐tri‐O‐benzyl‐3‐deoxy‐β‐D‐glycero‐D‐gulo‐heptonic acid (4) with diamino‐acid derivatives 8–14 in 83–96% yield. The synthesis of 4 was performed from 2‐(acetamido‐3,4,6‐tri‐O‐benzyl‐2‐deoxy‐β‐D‐glucopyranosyl) tributylstannane (2) by treatment with BuLi and CO2 in 83% yield. Similarly, propyl isocyanat yielded the glycoheptonamide 7 in 52% from 2. Compound 2 was obtained from 2‐acetamido‐3,4,6‐tri‐O‐benzyl‐2‐deoxy‐D‐glucopyranose (1) by chlorination and addition of tributyltinlithium in 74% yield. A procedure for a multigram‐scale synthesis of 1 is given.
Duplex Stability of 7‐Deazapurine DNA: Oligonucleotides containing 7‐bromo‐ or 7‐iodo‐7‐deazaguanine
Authors: Ramzaeva Natalya , Seela Frank 
Published: December 2004

AbstractThe oligonucleotide building blocks, the phosphonates 1a, b and the phosphoramidites 2a, b derived from 7‐iodo‐ and 7‐bromo‐7‐deaza‐2′‐deoxyguanosines 3a, b were prepared. They were employed in solid‐phase oligonucleotide synthesis of the alternating octamers d(Br7c7G‐C)4 (8) and d(I7c7G‐C)4 (9) as well as the homo‐oligonucleotides d[(Br7c7G)5‐G] (11) and d[(I7c7G)5‐G] (12). The melting profiles and CD spectra of oligonucleotide duplexes were measured. The Tm values as well as the thermodynamic data were determined and correlated to the major‐groove modification of this DNA. The self‐complementary octamers 8 and 9 form more stable duplexes compared to the parent oligomer d(G‐C)4. The heteroduplex of d[(I7c7G)5‐G] (12) with d(C6) is slightly destabilized (ΔTm = −12°) over that of d[(c7G)5‐G] with d(C6). However, the complex of 12 with poly(C) is more stable than that of d[(c7G5‐G)] with poly(C).
The Crystal and Molecular Structure of [Co(tmen)3](C7H7SO3)3·2 H2O and [Co(tmen)3](CH3SO3)2·EtOH·1/2 H2O (tmen = 2,3‐dimethylbutane‐2,3‐diamine)
Authors: Brunner Hans , Ludi Andreas , Raselli Andrea , Bürgi Hans‐Beat 
Published: December 2004

AbstractThe molecular structure of the two complex ions [Co(tmen)3]3+ and [Co(tmen)3]2+ (tmen = 2,3‐dimethylbutane‐2,3‐diamine) have been determined at 100 K. They show a strong trigonal distortion of the octahedral CoN6 core. The twist angle is 26.2(2.8)° for CoII and 43.9(9)° for CoIII. Average CoN distances are 2.193(13) Å (CoII) and 1.997(2) Å (CoIII), 0.02 Å longer than for the main body of CoIII amines.
Antiplatelet α‐Methylidene‐γ‐butyrolactones: Synthesis and evaluation of quinoline, flavone, and xanthone derivatives
Authors: Wang Tai‐Chi , Chen Yeh‐Long , Tzeng Cherng‐Chyi , Liou Shorong‐Shii , Chang Ya‐Ling , Teng Che‐Ming 
Published: December 2004

AbstractAs a continuation of our previous studies on the synthesis and antiplatelet activity of coumarin derivatives of α‐methylidene‐γ‐butyrolactones, certain quinoline, flavone, and xanthone derivatives were synthesized and evaluated for antiplatelet activity against thrombin (Thr)‐, arachidonic acid (AA)‐, collagen (Col)‐, and platelet‐activating factor (PAF)‐induced aggregation in washed rabbit platelets. These compounds were synthesized from quinolin‐8‐ol, flavon‐7‐ol, and xanthon‐3‐ol, respectively, via alkylation and Reformatsky‐type condensation (Schemes 1–3). By the comparison with comparison with coumarin α‐methylidene‐γ‐butyrolactone 3a, flavone and xanthone derivatives, 3b and 3c, respectively, are more selective in which only AA‐ and collagen‐induced aggregation are strongly inhibited. Most of the quinoline derivatives (9a–e) exhibited broad‐spectrum antiplatelet activities.
The Radical Ions of Dipleiadiene (Dicyclohepta[de,ij]naphthalene) and Its 12b,12c‐Homo Derivative. An ESR and ENDOR study
Authors: Bachmann Rainer , Gerson Fabian , Merstetter Pascal , Vogel Emanuel 
Published: December 2004

AbstractThe radical anions and the radical cations of dipleiadiene (dicyclohepta[de,ij]naphthalene; 1) and its 12b, 12c‐homo derivative 2 were characterized by ESR and ENDOR spectroscopy. Their singly occupied orbitals are related to the degenerate nonbonding MOs of a 16‐membered π‐perimeter. The π‐spin distribution over the perimeter is similar in the radical cations 1.+ and 2.+, and an analogous statement holds for the radical anions 1.− and 2.−. However, deviations of the π‐system from planarity lead to a decrease in the absolute values of the negative coupling constants of the perimeter protons in 2.+ and 2.− relative to those in 1.+ and 1.−. The hyperfine data for the perimeter protons in the radical ions correlate with the changes in 13C chemical shifts on passing from the neutral compounds to the corresponding diions. It is concluded from the coupling constants of the CH2 protons in the radical ions of 2 that the cation 2.+ exists in the methano‐bridged form (A) of the neutral 2 (and, presumably, also of the dication 22+), whereas the anion 2.− adopts the bisnorcaradiene form (B) of the dianion 22−.