bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diazo‐Transfer Reaction with Diphenyl Phosphorazidate
Authors: Villalgordo José M. , Enderli Adelheid , Linden Anthony , Heimgartner Heinz 
Published: December 2004

AbstractDiphenyl phosphorazidate (DPPA) was used as the azide source in a one‐pot synthesis of 2,2‐disubstituted 3‐amino‐2H‐azirines 1 (Scheme 1). The reaction with lithium enolates of amides of type 2, bearing two substituents at C(2), proceeded smoothly in THF at 0°; keteniminium azides C and azidoenamines D are likely intermediates. Under analogous reaction conditions, DPPA and amides of type 3 with only one substituent at C(2) gave 2‐diazoamides 5 in fair‐to‐good yield (Scheme 2). The corresponding 2‐diazo derivatives 6–8 were formed in low yield by treatment of the lithium enolates of N,N‐dimethyl‐2‐phenylacetamide, methyl 2‐phenylacetate, and benzyl phenyl ketone, respectively, with DPPA. Thermolysis of 2‐diazo‐N‐methyl‐N‐phenylcarboxamides 5a and 5b yielded 3‐substituted 1,3‐dihydro‐N‐methyl‐2H‐indol‐2‐ones 9a and 9b, respectively (Scheme 3). The diazo compounds 5–8 reacted with 1,3‐thiazole‐5 (4H)‐thiones 10 and thiobenzophenone (13) to give 6‐oxa‐1,9‐dithia‐3‐azaspiro[4.4]nona‐2,7‐dienes 11 (Scheme 4) and thiirane‐2‐carboxylic acid derivatives 14 (Scheme 5), respectively. In analogy to previously described reactions, a mechanism via 1,3‐dipolar cycloaddition, leading to 2,5‐dihydro‐1,3,4‐thiadiazoles, and elimination of N2 to give the ‘thiocarbonyl ylides’ of type H or K is proposed. These dipolar intermediates with a conjugated CO group then undergo either a 1,5‐dipolar electrocyclization to give spirohetrocycles 11 or a 1,3‐dipolar electrocyclization to thiiranes 14.
Syntheses of Biphenyl Analogues of AP7, a New Class of Competitive N‐Methyl‐D‐aspartate (NMDA) Receptor Antagonists
Authors: Müller Werner , Kipfer Peter , Lowe David A. , Urwyler Stephan 
Published: December 2004

AbstractSyntheses of a series of enantiomerically pure, substituted analogues 7b–t of SDZ EAB 515 (7a) were described (Schemes 1 and 2). Affinites for the NMDA receptor were measured ([3H]CGP‐39653 binding assay) and competitive NMDA antagonistic potencies determined in a functional test (rat neocortical slice preparation). Structure‐activity relationships show that attachment of an OH group at position 4 of the chain‐inserted benzene ring of the biphenyl moiety and/or expansion of the angle between the planes of the two benzene rings by ortho‐substituents increase in vitro activities into the low nanomolar range.
Die Reduktion von Azulen mit Natrium zum Kontaktionen‐Tripel [Dinatrium‐(1,1′,6,6′‐Tetrahydro‐6,6′‐bi(azulen)‐1,1′‐diid)–bis (diglyme)]∞
Authors: Bock Hans , Arad Claudia , Näther Christian , Göbel Ilka 
Published: December 2004

The Sodium Reduction of Azulene to the Contact‐Ion Triple [Disodium‐(1,1′,6,6′‐Tetrahydro‐6,6′‐bi(azulene)‐1,1′‐diide)–bis(diglyme)]∞Colorless air‐sensitive single crystals can be grown from a diglyme solution after the reduction of azulene by a Na‐metal mirror. Structure determination at 150 K reveals a dimer dianion, in which the seven‐membered rings are connected in 6,6′‐positions and doubly diglyme‐solvated Na+ counter cations η5‐coordinate to the five‐membered rings. Based on preceding cyclovoltammetric measurements in aprotic azulene solutions as well as on extensive MNDO enthalpy of formation calculations, a proposal is forwarded how possibly the contact ion triple is formed along a microscopic pathway.
Preparation, Structure, and Reactivity of Thioxo and Imino Derivatives of the Triolide (and Pentolide) from (R)‐3‐Hydroxybutanoic Acid
Authors: Brunner Andreas , Kühnle Florian N. M. , Seebach Dieter 
Published: December 2004

AbstractReaction of the triolide 1 from (R)‐3‐hydroxybutanoic acid with Lawesson's reagent 5 leads to the mono‐, di‐, and trithio derivatives 6–8 which can be isolated in pure form (20–40% yields), and which have crystal structures very similar to the parent triolide 1 (Fig. 1). Similarly, pentolide 3 is converted to mixtures of various thio derivatives, three of which are separated (10–12) by HPLC and fully characterized. The X‐ray structures of the mono‐ and of one of the dithiopentolides (10, 12) differ remarkably from each other (Fig. 3). Reduction of the thiotriolides 6–8 (NaBH4, R3SnH, Cl3SiH, Raney‐Ni) gives 12‐membered rings containing up to three ether groups (chiral crown ethers, 15, 17–19) in poor yields. The thiotriolides react spontaneously and in yields of up to 96% with ammonia, certain primary amines, and hydroxylamine to give imine and oxime derivatives with intact 12‐membered‐ring backbones (20, 22–24, 30, see crystal structures in Figs. 4–7). The rigid structure of all the derivatives of triolide 1 puts the CO, CS, and CNR O‐, S‐, and N‐atoms in juxtaposition (a feature reminiscent of the side chains in the iron‐binder enterobactin, Fig. 6). Imines containing PPh2 groups are prepared (30, 33, 35) from the thiotriolides and tested as chiral ligands for PdII‐catalyzed 1,3‐diphenyallylations (→ 37, enantiomer ratio up to 77:23). The reactions described demonstrate that multiple reactions of the triolide 1 from (R)‐3‐hydroxybutanoic acid which proceed through tetrahedral intermediates are possible without ring opening – the skeleton is remarkably stable, and this might be exploited as a template for bringing up to three pendent substituents into close proximity to allow a study of their interactions and cooperative properties. Also, the di‐ and trithio derivatives 7 and 8 could be used for cross‐linking in molecules containing primary NH2 groups.
Channel‐Forming Activity of 3‐Hydroxybutanoic‐Acid Oligomers in Planar Lipid Bilayers
Authors: Seebach Dieter , Brunner Andreas , Michael Büger H. , Reusch Rosetta N. , Bramble Linda L. 
Published: December 2004

AbstractMonodisperse and polydisperse oligomers and polymers of 3‐hydroxybutanoic acid (3‐HB) containing 8, 16, ca. 28, 32, ca. 60, 64, 96, and ca. 3000 monomer units were incorporated into palmitoyl‐oleoyl‐phosphatidyl choline (POPC) planar bilayers. At concentrations of 0.1–5% of oligo(3‐HB), the resulting phospholipid bilayers showed typical single‐channel behavior for Rb+ and Ba2+ ions, using the patch clamp technique. Thus, channel‐forming activity of a pure polyester has been demonstrated for the first time (Figs. 1, 3, and 6). Single‐channel activity depends upon the following structural parameters of the 3‐HB derivatives: unprotected OH and COOH groups on the chain ends; chain length ⩾ 16 monomer units; no high‐molecular‐weight as in P(3‐HB). The results are discussed in view of the Ca2+‐specific channel formed with the P(3‐HP)/Ca · PPi complex from genetically competent Escherichia coli and in view of the ubiquitous occurrence of low‐molecular‐weight P(3‐HB) in prokaryotic and eukaryotic organisms. A simple model for the channel‐causing structure is proposed, based on the proven tendency of oligo‐ and poly(3‐HB) to form ca. 50‐Å thick lamellar crystallites.
Hydrolytic Breakdown of the Euplotins, Highly Strained, Adaptive, Hemiacetal Esters of the Marine Ciliate Euplotes crassus: A Mimic of Degradative Pathways in Nature and a Trick for the Assignment of the Absolute Configuration
Authors: Guella Graziano , Pietra Francesco , Dini Fernando 
Published: December 2004

AbstractEuplotin C((+)‐3), the most abundant of the niche‐exploitation terpenoids of the marine ciliate morphospecies Euplotes crassus, was found to undergo degradation in mildly basic H2O/MeOH by initial hydrolysis of the acetate group, followed by, in turn, hydrolytic ring‐A and ring‐C opening and ring‐A reclosure with indiscriminate C(1)/C(15) methanol trapping to give four diastereoisomeric aldehydic hemiacetals 5–8 in similar proportions; 7, as a model for its congeners, proved biologically inactive. From these, the absolute configuration was assigned via Mosher's ester methodology. These processes may be assumed to mimic inactivation of the euplotins in sea water. Degradation of (+)‐3 in either stronger base or acidic medium was also examined.
Nonreductive Enantioselective Ring Opening of N‐(Methylsulfonyl)dicarboximides with Diisopropoxytitanium α,α,α′,α′‐Tetraaryl‐1,3‐dioxolane‐4,5‐dimethanolate
Authors: Ramón Diego J. , Guillena Gabriela , Seebach Dieter 
Published: December 2004

AbstractThe bicyclic and tricyclic meso‐N‐(methylsulfonyl)dicarboximides 1a–f are converted enantioselectively to isopropyl [(sulfonamido)carbonyl]‐carboxylates 2a–f by diisopropoxytitanium TADDOLate (75–92% yield; see Scheme 3). The enantiomer ratios of the products are between 86:14 and 97:3, and recrystallization from CH2Cl2/hexane leads to enantiomerically pure sulfonamido esters 2 (Scheme 3). The enantioselectivity shows a linear relationship with the enantiomer excess of the TADDOL employed (Fig.3). Reduction of the ester and carboxamide groups (LiAlH4) and additional reductive cleavage of the sulfonamido group (Red‐Al) in the products 2 of imide‐ring opening gives hydroxy‐sulfonamides 3 and amino alcohols 4, respectively (Scheme 4). The absolute configuration of the sulfonamido esters 2 is determined by chemical correlation (with 2a,b; Scheme 6), by the X‐ray analysis of the camphanate of 3e (Fig. 1), and by comparative 19F‐NMR analysis of the Mosher esters of the hydroxy‐sulfonamides 3 (Table 1). A general proposal for the assignment of the absolute configuration of primary alcohols and amines of Formula HXCH2CHR1R2, X = O, NH, is suggested (see 11 in Table 1). It follows from the assignment of configuration of 2 that the Re carbonyl group of the original imide 1 is converted to an isopropyl ester group. This result is compatible with a rule previously put forward for the stereochemical course of reactions involving titanium TADDOLate activated chelating electrophiles (12 in Scheme 7). A tentative mechanistic model is proposed (13 and 14 in Scheme 7).
Oligosaccharide Analogues of Polysaccharides. Part 8. Orthogonally Protected Cellobiose‐Derived Dialkynes. A Convenient Method for the Regioselective Bromo‐ and Protodegermylation of Trimethylgermyl‐ and Trimethylsilyl‐protected Dialkynes
Authors: Ernst Alexander , Vasella Andrea 
Published: December 2004

AbstractThe cellobiose‐derived dialkynes 14 and 15 were prepared by glycosidation of the acceptor 9 with the thioglycosides 12(82%) and 13(85%), respectively. The acceptor 9 was prepared from the known alcohol 2 via the lactone 7 in five steps (48% overall), and the donors 12 and 13 were prepared from the alkynylated anhydroglucose derivative 10 (60% overall). Acetolytic debenzylation of 14 and 15 (→16 and 17, resp.) followed by deacylation of 16 yielded 60% of the cellobiose‐derived dialkyne 18. Deacylation of 14 (→19), methoxymethylation (→20) and trimethylgermylation led to the orthogonally protected dialkyne 21 (69% overall). Protodesilylation of 21 with K2CO3/MeOH gave 22 (90%), while the Me3Ge group was selectively removed with CuBr (19 mol‐%) in THF/MeOH to give 20 (95%). Treatment of 21 with aqueous HCl solution led to 19 (80%). Bromodegermylation of 21 (NBS/AgOOCCF3) led to a mixture of 23 (85%) and 24 (11%). Similar conditions using CuBr instead of AgOOCCF3 gave exclusively the bromoalkyne 23 (93%). The temperature dependence of the δ values of the OH resonances of 18 in (D6)DMSO evidence a strong intramolecular H‐bond between C(5′)O…︁HOC(5).
Synthese von Trifluoromethyl‐substituierten Schwefel‐Heterocyclen unter Verwendung von 3,3,3‐Trifluorobrenztraubensäure‐Derivaten
Authors: Mlostoń Grzegorz , Gendek Tomasz , Heimgartner Heinz 
Published: December 2004

Synthesis of Trifluoromethyl‐Substituted Sulfur Heterocycles Using 3,3,3‐Trifluoropyruvic‐Acid DerivativesThe reaction of methyl 3,3,3‐trifluoropyruvate (1) with 2,5‐dihydro‐1,3,4‐thiadiazoles 4a, b in benzene at 45° yielded the corresponding methyl 5‐(trifluoromethyl)‐1,3‐oxathiolane‐5‐carboxylates 5a, b (Scheme 1) via a regioselective 1,3‐dipolar cycloaddition of an intermediate ‘thiocarbonyl ylide’ of type 3. With methyl pyruvate, 4a reacted similarly to give 6 in good yield. Methyl 2‐diazo‐3,3,3‐trifluoropropanoate (2) and thiobenzophenone (7a) in toluene underwent a reaction at 50°; the only product detected in the reaction mixture was thiirane 8a (Scheme 2). With the less reactive thiocarbonyl compounds 9H‐xanthene‐9‐thione (7b) and 9H‐thioxanthene‐9‐thione (7c) as well as with 1,3‐thiazole‐5(4H)‐thione 12, diazo compound 2 reacted only in the presence of catalytic amounts of Rh2(OAc)4. In the cases of 7a and 7b, thiiranes 8b and 8c, respectively, were the sole products (Scheme 3). The crystal struture of 8c has been established by X‐ray crystallography (Fig.). In the reaction with 12, desulfurization of the primarily formed thiirane 14 gave the methyl 3,3,3‐trifluoro‐2‐(4,5‐dihydro‐1,3‐thiazol‐5‐ylidene)propanoates (E)‐and (Z)‐15 (Scheme 4). A mechanism of the Rh‐catalyzed reaction via a carbene addition to the thiocarbonyl S‐atom is proposed in Scheme 5.
A Non‐Racemic Equivalent of Glycolic Acid: Preparation of both enantiomers from D‐mannitol
Authors: Renaud Philippe , Abazi Sokol 
Published: December 2004

AbstractA practical synthesis of both enantiomers of 2‐(tert‐butyl)‐2‐methyl‐1,3‐dioxolan‐4‐one starting from D‐mannitol is reported. These compounds are chiral equivalents of glycolic acid (= hydroxyacetic acid) which are configurationally stable and can be alkylated via their enolates.
Mechanistic Details of the Fe+‐Mediated CC and CH Bond Activations in Propane: A Theoretical Investigation
Authors: Holthausen Max C. , Koch Wolfram 
Published: December 2004

AbstractQuantum‐chemical calculations employing a density‐functional theory/Hartree‐Fock hybrid method (B3LYP) have been used to explore the mechanistic details of the CC and CH bond‐activation processes in propane mediated by a bare Fe+ ion. While the theoretically predicted results are in complete accord with all available experimental data, they give rise to a different mechanistic picture than envisaged previously. In contrast to earlier speculation, the activation barriers for the initial insertion steps of Fe+ into a CH or CC bond are found to be significantly below the Fe+ + C3H8 channel. The rate‐determining steps for both, the CC and the CH bond activation branches of the [FeC3H8]+ potential‐energy surface rather occur late on the respective reaction coordinates and are connected with saddle points of concerted rearrangement processes. The CC bond activation, which leads to the exothermic reductive elimination of methane, occurs via the CC inserted species and not as a side channel originating from a CH inserted ion, as assumed hitherto. For the CH bond‐activation processes, which finally results in the exothermic expulsion of molecular hydrogen, two energetically similar reaction channels for an [1,2]‐elimination exist. The results clearly show, that an [1,3]‐H2‐elimination mechanism cannot compete with the [1,2]‐elimination paths, in line with the experimental findings. Overall, a lower energy demand for the reductive elimination of methane compared to the loss of H2 is obtained, straightforwardly explaining the preference of the former process observed experimentally.
Oligosaccharide Analogues of Polysaccharides. Part 9. Synthesis and Thermolysis of Acetylenosaccharide‐Derived 1,2‐Dialkynylbenzenes
Authors: Xu Jinwang , Egger Anita , Bernet Bruno , Vasella Andrea 
Published: December 2004

AbstractThermolysis of the 1,2‐bis(glucosylalkynyl)benzenes 6 and 16 was studied to evaluate the effects of intramolecular H‐bonding on the activation energy of the Bergman‐Masamune‐Sondheimer cycloaromatization, and to evaluate the use of the cycloaromatization for the synthesis of di‐glycosylated naphthalenes. The dialkynes were prepared by cross‐coupling of the O‐benzylated or O‐silylated glucosylalkynes 1 and 4 (Scheme 1). Thiolysis of the known 1, or acetolysis of 1, followed by deacetylation (→2→3) and silylation gave 4. Cross‐coupling of 1 or 4 with iodo‐ or 1,2‐diiodobezene depended upon the nature of the added amine and on the protecting group, and led to the mono‐ and dialkynylbenzenes 5 and 6, or 12, 13, and 15, respectively. The benzyl ethers 5 and 6 gave poor yields upon acetolysis catalyzed by BF3 · OEt2, while Ac2O/CoCl2 · 6 H2O transformed 6 in good yields into the regioselectively debenzylated 10. Desilylation of 7 and 13 gave the alcohols 8 and 14, respectively. Thermolysis of 6 in PhCl gave 22 and 23, independently of the presence or absence of 1,4‐cyclohexadiene; 23 was formed from 22 (Scheme 2). Acetolysis of 22 gave the hexaacetate 24 that was completely debenzylated by thiolysis, yielding the diol 26 and trans‐stilbene, evidencing the nature and position of the bridge between the glucosyl moieties (Scheme 3). Thiolysis of 22 yielded the unprotected 2,3‐diglucosylnaphthalene 28, a new type of C‐glycosides. Depending upon conditions, hydrogenation of 22 led to 29 (after acetylation), 30, or 32. NMR and particularly NOE data evidence the threo‐configuration of the bridge. The structure of 23 was confirmed by hydrolysis to the diol 34 and diphenylacetaldehyde, and by correlation of 23 with 22 via the common product 31. Formation of 22 is rationalized by a Bergman cyclization to a diradical, followed by regioselective abstraction of a H‐atom from the BnOC(2) group, and diastereoselective combination of the doubly benzylic diradical (Scheme 4). While thermolysis of 3 in EtOH sets in around 140°, 16 did not react at 160° and decomposed at 180–220°. No evidence for intramolecular H‐bonds of 16, as compared to 14, were found.
Probing the Helical Secondary Structure of Short‐Chain β‐Peptides
Authors: Seebach Dieter , Ciceri Paola E. , Overhand Mark , Jaun Bernhard , Rigo Dario , Oberer Lukas , Hommel Ulrich , Amstutz René , Widmer Hans 
Published: December 2004

AbstractStructural prerequisites for the stability of the 31 helix of β‐peptides can be defined from inspection of models (Figs. 1 and 2): lateral non‐H‐substituents in 2‐ and 3‐position on the 3‐amino‐acid residues of the helix are allowed, axial ones are forbidden. To be able to test this prediction, we synthesized a series of heptapeptide derivatives Boc‐(β‐HVal‐β‐HAla‐β‐HLeu‐Xaa‐β‐HVal‐β‐HAla‐β‐HLeu)‐OMe 13–22 (Xaa = α‐ or β‐amino‐acid residue) and a β‐depsipeptide 25 with a central (S)‐3‐hydroxybutanoic‐acid residue (Xaa = –OCH(Me)CH2C(O)–) (Schemes 1 3). Detailed NMR analysis (DQF‐COSY, HSQC, HMBC, ROESY, and TOCSY experiments) in methanol solution of the β‐hexapeptide H(‐β‐HVal‐β‐HAla‐β‐HLeu)2‐OH (1) and of the β‐heptapeptide H‐β‐HVal‐β‐HAla‐β‐HLeu‐(S,S)‐β‐HAla(αMe)‐β‐HVal‐β‐HAla‐ β‐HLeu‐OH (22), with a central (2S,3S)‐3‐amino‐2‐methylbutanoic‐acid residue, confirm the helical structure of such β‐peptides (previously discovered in pyridine solution) (Fig.3 and Tables 1–5). The CD spectra of helical β‐peptides, the residues of which were prepared by (retentive) Arndt‐Eistert homologation of the (S)‐ or L‐α‐amino acids, show a trough at 215 nm. Thus, this characteristic pattern of the CD spectra was taken as an indicator for the presence of a helix in methanol solutions of compounds 13–22 and 25 (including partially and fully deprotected forms) (Figs.4–6). The results fully confirm predicted structural effects: incorporation of a single ‘wrong’ residue ((R)‐β‐HAla, β‐HAib, (R,S)‐β‐HAla(α Me), or N‐Me‐β‐HAla) in the central position of the β‐heptapeptide derivatives A (see 17, 18, 20, or 21, resp.) causes the CD minimum to disappear. Also, the β‐heptadepsipetide 25 (missing H‐bond) and the β‐heptapeptide analogs with a single α‐amino‐acid moiety in the middle (13 and 14) are not helical, according to this analysis. An interesting case is the heptapeptide 15 with the central achiral, unsubstituted 3‐aminopropanoic‐acid moiety: helical conformation appears to depend upon the presence or absence of terminal protection and upon the solvent (MeOH vs. MeOH/H2O).
Biosynthesis of δ‐Jasmin Lactone ( = (Z)‐Dec‐7‐eno‐5‐lactone) and (Z,Z)‐Dodeca‐6,9‐dieno‐4‐lactone in the Yeast Sporobolomyces odorus
Authors: Haffner Thomas , Nordsieck Andreas , Tressl Roland 
Published: December 2004

Abstract(all‐Z)‐(9,10,12,13,15,16‐2H6)Octadeca‐9,12,15‐trienoic acid ( = α‐linolenic acid; D6‐4) was synthesized to investigate the biochemical formation of linolenic‐acid‐derived aroma compounds in cultures of the yeast Sporobolomyces odorus, using an established gas chromatographic/mass spectrometric (GC/MS) method. Three compounds were identified as labeled: (Z)‐dec‐7‐eno‐5‐lactone (δ‐jasmin lactone), (Z,Z)‐dodeca‐6,9‐dieno‐4‐lactone, and (2E,4Z)‐hepta‐2,4‐dienoic acid. Both lactones were biosynthesized mostly under conservation of the initial configuration from their corresponding oxygenated linolenic‐acid intermediates. The application of (13S,9Z,11E,15Z)‐13‐hydroxy(9,10,12,13,15, 16‐2H6)octadeca‐9,11,15‐trienoic acid (D6‐7) as a OH‐functionalized precursor of δ‐jasmin lactone allowed to gain insight into the stereochemical course of the biosynthesis to both enantiomers of this lactone. In this experiment, 88.3% of the metabolized labeled precursor was transformed under retention of the original configuration of the (R)‐enantiomer. This investigation is also a contribution to a better understanding of the CC bond isomerization steps which took place during the β‐oxidative degradation of the substrate.
Nucleosides. Part LXI. A Simple Procedure for the Monomethylation of Protected and Unprotected Ribonucleosides in the 2′‐O‐ and 3′‐O‐Position Using Diazomethane and the Catalyst Stannous Chloride
Authors: Cramer Hagen , Pfleiderer Wolfgang 
Published: December 2004

AbstractIntensive studies on the diazomethane methylation of the common ribonucleosides uridine, cytidine, adenosine, and guanosine and its derivatives were performed to obtain preferentially the 2′‐O‐methyl isomers. Methylation of 5′‐O‐(monomethoxytrityl)‐N2‐(4‐nitrophenyl)ethoxycarbonyl‐O6‐[2‐(4‐nitrophenyl)ethyl]‐guanosine (1) with diazomethane resulted in an almost quantitative yield of the 2′‐ and 3′‐O‐methyl isomers which could be separated by simple silica‐gel flash chromatography (Scheme 1). Adenosine, cytidine, and uridine were methylated with diazomethane with and without protection of the 5′ ‐O‐position by a mono‐ or dimethoxytrityl group and the aglycone moiety of adenosine and cytidine by the 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) group (Schemes 2–4). Attempts to increase the formation of the 2′‐O‐methyl isomer as much as possible were based upon various solvents, temperatures, catalysts, and concentration of the catalysts during the methylation reaction.
Development of Luminescent Terbium(III) Chelates for Protein Labelling: Effect of triplet‐state energy level
Authors: Takalo Harri , Mukkala Veli‐Matti , Meriö Liisa , Rodríguez‐Ubis Juan Carlos , Sedano Rosa , Juanes Olga , Brunet Ernesto 
Published: December 2004

AbstractThe synthesis of novel TbIIIlabels suitable for protein labelling are reported. Their luminescence properties as antibody conjugates were measured and compared to the results of corresponding TbIIIchelates of the parent ligand structures. When the lowest triplet‐state energy level of the parent donor ligand was over 23000 cm−1,i.e., the energy gap between the5D4level of TbIIIand the lowest triplet‐state energy level of the ligand exceeded 2600 cm−1, the label derivative with a long decay time (τ = 1.35–2.93 ms) and a high luminescence yield (ϵ. Φ = 3770–4560) was found to be suitable for bioaffinity assays.
Diastereoselective Synthesis of Cyclododeca‐1,6‐diallenes ( = cyclododeca‐l,2,6,7‐tetraenes)
Authors: Boss Christoph , Keese Reinhart 
Published: December 2004

AbstractThe synthesis of substituted cyclododeca‐1,6‐diallenes.( = cyclododeca‐1,2,6,7‐tetraenes) from cyclododeca‐5,11‐diyne‐1,4‐diols is described (Schemes 1 and 3). The ca. 1:1 mixtures of the stereoisomers of the cyclododeca‐1,6‐diallenes were formed in high yields from the ca. 1:1 diastereoisomer mixtures of the 1,4‐disubstituted cyclododeca‐5,11‐diynes by reactions with Me2CuLi or t‐BuMgCl/CuII. In mechanistically relevant experiments with the pure diastereoisomers of 1,4‐dimethylcyclododeca‐5,11‐diyne‐1,4‐diol, it is demonstrated that the configuration is conserved in these reactions. The first synthesis of a 1‐substituted cyclododeca‐2,8‐diyne bearing only one propargylic leaving group gives access to a mixed 12‐membered allen‐yne (Scheme 5).