bluuebunny/crossref_metadata_2025_split huggingface dataset:
α,α,α′,α′‐Tetraaryl‐1,3‐dioxolane‐4,5‐dimethanols (TADDOLs) for Resolutions of Alcohols and as Chiral Solvating Agents in NMR Spectroscopy
Authors: Von Dem Bussche‐Hünnefeld Christoph , Beck Albert K. , Lengweiler Urs , Seebach Dieter 
Published: December 2004

AbstractThe use of α,α,α′,α′ ‐tetraaryl‐1,3‐dioxolane‐4,5‐dimethanols ( = TADDOLs;1) as chiral NMR shift reagents (1H, 13C, 19F) is described. In many cases, the ratio of enantiomeric alcohols and amines can be determined under standard conditions of measurement (CDCl3 as solvent, room temperature). The preparation and use of a new type of TADDOL, the tetrakis(dimethylamino) derivative 1d, is described. Menthol, octan‐2‐ol, and oct‐1‐yn‐3‐ol are partially resolved by crystallization of clathrates with 1c and 1d.
Synthese und Reaktionsverhalten 2′‐substituierter Isoflavone
Authors: Süsse Manfred , Johne Siegfried , Hesse Manfred 
Published: December 2004

Synthesis and Behaviour of Isoflavones Substituted in 2′‐PositionThe protected chalcones 6–8 prepared from acetophenone and benzaldehydes rearranged to the dimethoxypropanone derivatives 9–11 in the presence of trimethyl orthoformate by Tl(NO3)3. 3 H2O. These compounds could be cyclized to the isoflavones 12–14 in high yields (Scheme 2). The conversion of these isoflavones to the corresponding isoflavanes (model compounds of the phytoalexin glabridin; see Scheme 1) was the main goal of this work. Hydrogenation of 13 and 14 gave the isoflavanes 15 and 16, respectively and their deprotection the racemic natural product 4′‐O‐demethylvestitol (17). Reduction of 13 and 14 yielded different compounds depending on the reducing agent (Scheme 3). The saturated alcohols 20–23 could be obtained with NaBH4 or LiBH4. They were transferred into the racemic 9‐O‐demethylmedicarpin (24) and haginin D (25) under acidic conditions. The ketones 26–28 (Scheme 4) were obtained in high yields by reduction of 12–14 with DIBAH. Deprotection of 26 yielded the racemic 2,3‐dihydrodaidzein (29). Compounds 13 and 27 as well as 20 and 22 showed different behaviour under reduction conditions with Li in liquid ammonia. An efficient method for the introduction of the MeOCH2O and the MeOCH2CH2OCH2 protecting groups into hydroxylated benzaldehydes and acetophenones (Scheme 5) is described. The appropriate experimental conditions depend on the regioselectivity and on the number of the protected groups. The protected aldehydes, especially those with a protected ortho OH group, show an extraordinary ionization behaviour in chemical‐ionization mass spectrometry (isobutane; Scheme 6).
The Isotopomeric (Z)‐ and (E)‐2,3‐Dimethyl(1,1,1,4,4,4‐2H6)but‐2‐enes: Mechanistic Probes for Stereospecific Epoxidation
Authors: Müller Paul , Pfyffer Jean 
Published: December 2004

AbstractBy unambiguous methods, (Z)‐ and (E)‐2, 3‐dimethyl(1, 1, 1, 4, 4, 4‐2H6)but‐2‐enes (3) were synthesized and transformed to the epoxides 4 with 3‐chloroperbenzoic acids. Both the isotopomeric olefins and the epoxides are detected separately by 1H‐NMR at 400 MHz. Epoxidation of (Z)‐3 with [RhICl(PPh3)3]/cumene hydroperoxide resulted in a 1: 1 mixture of (Z)‐ and (E)‐4, while reaction of (Z)‐3 with [FeIII(tpp)]Cl/PhIO gave only (Z)‐4 (tpp = tetraphenylporphyrin).
Absolute Configuration and Synthesis of (+)‐Caudoxirene, the Gamete‐Releasing and Gamete‐Attracting Pheromone of the Brown Alga Perithalia caudata (Phaeophyceae)
Authors: Wirth Dieter , Boland Wilhelm , Müller Dieter G. 
Published: December 2004

AbstractThe absolute configuration of the gamete‐releasing and ‐attracting pheromone 2‐vinyl‐3‐(5′‐vinylcyclopent‐2′‐enyl)oxirane ( =(+)‐caudoxirene; (+)‐1) of the marine brown alga Perithalia caudata is established as (2R,3R,1′S,5′S). Highly diastereoselective syntheses and the biological activities of three diastereoisomers of 1 are described. Compound (+)‐(2R,3R,1′S,5′S)‐1 is the first fully characterized epoxypheromone from marine brown algae (Phaeophyceae).
Fluoro‐Analoga von Cycloheptadien‐Pheromonen mariner Braunalgen: ungewöhnlich leicht verlaufende [3,3]‐sigmatrope Umlagerung eines trans‐di(alkenyl)‐substituierten geminalen Difluorocyclopropans
Authors: Erbes Petra , Boland Wilhelm 
Published: December 2004

Fluoro Analoga of Cycloheptadiene Pheromones of Marine Brown Algae: Exceptionally Facile [3,3]‐Sigmatropic Rearrangement of a trans‐Di(alkenyl)‐Substituted Geminal DifluorocyclopropaneThe 3,3,‐difluorocyclopropane‐1,2‐dicarbonyl compounds 9a and 9b are obtained by addition of difluorocarbene to methyl cinnamate or trans‐stilbene followed by oxidative degradation of the phenyl rings(s) (Scheme 2). Compound 9b is a versatile building block for the synthesis of the di(alkenyl)‐substituted geminal difluorocyclopropane 5 or the chrysanthemum ester 10b. Cyclopropane 5 is unstable at room temperature and rearranges to the 3,3,‐difluorocyclohepta‐1,4‐diene 4, an analog of the algal pheromone dictyotene (1; Scheme 3). The kinetic parameters of the [3,3]‐sigmatropic rearrangement are determined. The data support the view that a geminal difluoro group within a cyclopropane weakens the distal bond.
Synthesis and N‐Methyl‐D‐aspartate (NMDA) Antagonist Properties of the Enantiomers of α‐Amino‐5‐(phosphonomethyl)[1,1′‐biphenyl]‐3‐propanoic Acid. Use of a New Chiral Glycine Derivative
Authors: Müller Werner , Lowe David A. , Neijt Hans , Urwyler Stephan , Herrling Paul L. , Blaser Denis , Seebach Dieter 
Published: December 2004

AbstractThe enantiomers of the title compound, 7a and ent‐7a, and of substituted analogues are synthesized. The absolute configuration of 7a is deduced from that of (tert‐butyl 2‐tert‐butyl)‐3‐methyl‐4‐oxoimidazolidin‐1‐carboxylate (15) and from the trans‐configuration of the intermediate 17a which in turn is assigned on the basis of 1H‐NMR nuclear Overhauser effect (NOE) measurements. Instead of 15, the 2‐isopropyl‐substituted analogue 21 can also be employed. Its preparation from glycine, methylamine, isobutyraldehyde, and (Boc)2O, and the resolution through the bis‐O,O′‐(4‐toluyl)tartrate salt 20 are described. In two functional tests (rat neocortical slice and frog hemisected spinal cord preparation) the (S)‐enantiomer 7a (SDZ EAB 515) is shown to be a very potent, selective competitive NMDA antagonist.
An Efficient Synthesis of Racemic 4‐Hydroxy‐2‐oxo‐1‐pyrrolidineacetamide (Oxiracetam) Using Tetramic‐Acid Intermediates
Authors: Laffan David D. P. , Bänziger Markus , Duc Lauren , Evans Andrew R. , McGarrity John F. , Meul Thomas 
Published: December 2004

AbstractThe title compund, 1a, has been synthesised in racemic form from ethyl (E)‐4‐chloro‐3‐ethoxybut‐2‐enoate in 43% overall yield in five steps. Several routes to the final product are described, but the most efficient involves hydrogenation of a C(5)‐unsubstituted tetramic acid 5b. The instability of this class of compounds required the use of a catalyst which could operate under very acidic aqueous conditions, a role that was successfully filled by a 5% Ru/C catalyst.
Electron‐Transfer‐Catalyzed cis → trans Isomerization of 1,1′‐Azonorborane. Prototype of a reversible two‐stage storage system
Authors: Gescheidt Georg , Lamprecht Axel , Heinze Jürgen , Schuler Barbara , Schmittel Michael , Kiau Susanne , Rüchardt Christoph 
Published: December 2004

AbstractESR and cyclic voltammetry investigations show that isomerization of the radical cation of cis‐1,1′‐azonorbornane (cis‐1) to the trans‐radical ion proceeds too fast in solution for direct investigation of the cis‐radical ion even at −78°. The facile isomerization of the radical cation is in agreement with PM3 calculations proposing an activation barrier of only 17 kJ/mol. As a consequence, quantitative cis → trans isomerization of 1,1′‐azonorbornane can effectively be accomplished by addition of catalytic amounts of one‐electron oxidants. This is the first evidence for a radical‐cation‐catalyzed cis → trans isomerization of azo compounds.
Carbocyclic analogs of nucleosides. Part 2.. Synthesis of 2′,3′‐dideoxy‐5′‐homonucleoside analogs
Authors: Jenny Thomas F. , Horlacher Jennifer , Previsani Nicoletta , Benner Steven A. 
Published: December 2004

AbstractA set of derivatives of cyclopentaneacetic acid cis‐substituted at position 3 by nucleoside bases (both purines and pyrimidines) were prepared and characterized (see 11, 14, and 23a, b; Schemes 2–4). These molecules are carbocyclic analogs of 2′,3′‐dideoxy‐5′‐homonucleosides. In this synthesis, the skeleton was constructed from norbornanone and a novel method based on Mitsunobu chemistry used for the introduction of nucleoside‐base substituents. The scope of this method was further explored via the preparation of a cyclobutyl analog of dideoxyguanosine (see 17, Scheme 3).
Conformational Studies of Marine Polyhalogenated α‐Chamigrenes Using Temperature‐Dependent NMR Spectra. Cyclohexene‐ring flipping and rigid‐chair cyclohexane ring in the presence of equatorial halogen atoms at C(8) and C(9)
Authors: Guella Graziano , Chiasera Giuseppe , Pietra Francesco 
Published: December 2004

AbstractTemperature‐dependent NMR spectra indicate that the α‐chamigren‐3‐ones (−)‐11, (+)‐12, (+)‐14 (−)‐15, (+)‐16, 18, and 19 bearing equatorial halogen atoms at C(8) and C(9) undergo slow conformational flipping of the envelope‐shaped enone ring, while the cyclohexane ring is maintained in the chair conformation. The α‐chamigren‐3‐ols (+)‐20 and (+)‐21, obtained by hydride reduction of (+)‐12, behave similarly, with slow half‐chair inversion of the cyclohexenol ring. In each case, both conformers are about equally populated and detectable by NMR, except in the case of (+)‐15, where repulsive interactions between BrC(2) and Heq−C(7) make the population of the conformer 15b with Me—C(5) faced to Hax−C(10) so low that it escapes direct 1H‐NMR detection. The energy barriers to these conformational motions are viewed to arise mainly from repulsive interactions between Me—C(5) and the axial H‐atoms at C(8) and C(10), while, contrary to previous beliefs, no twist‐boat conformations of the cyclohexane ring intervene. Similar conclusions hold for the 4,5‐epoxides of both (−)‐6 and (+)‐7. Clean Jones oxidatio of (−)‐2 to 17, where the CH2C(5) bond is maintained, and acid dehydration‐isomerization of the α‐chamigrene (+)‐21 to the β‐chamigrene (+)‐24, reflect the special stability of β‐chamigrenes, providing a reason for their frequent occurrence in nature.
Investigations of Steric and Electronic Factors Influencing the Cyclopalladation of meta‐Toluidine Analogues
Authors: Mossi Waldo , Klaus Alfred J. , Rys Paul 
Published: December 2004

AbstractThe cyclopalladation of two different types of aniline derivatives is described: the acetylated anilines N‐(3‐methylphenyl)acetamide (2a), 3‐(acetylamino)‐4‐chlorobenzoic acid (2c), and N‐(2‐chlorophenyl)acetamide (2d) are cyclometalated easily with palladium(II) acetate and trifluoroacetic acid to yield the corresponding complexes 4a, 4c, and 4d, respectively, whereas the acetylated meta‐toluidine N‐(2‐chloro‐5‐methylphenyl)acetamide (2b) cannot be metalated at the only accessible site between the acetylamino and the methyl group. This aromatic CH bond can be activated, however, with the second type of meta‐toluidine derivatives: the 2‐chloro‐5, N‐dimethyl‐N‐nitrosoaniline (3b) readily undergoes cyclopalladation to yield the corresponding PdII complex di‐μ‐trifluoro‐acetato‐bis[3‐chloro‐6‐methyl‐2‐(N‐methyl‐N‐ nitrosoamino)phenyl‐C,NO]dipalladium(II) (5b) containing a five‐membered palladacycle with coordination of PdII at the nitroso N‐atom, which is established by 15N‐NMR spectroscopy.
Synthesen der Phosphono‐ bzw. Phosphino‐Analoga des Pantothensäure‐ethylesters und des Phosphono‐Analogons des Pantetheins
Authors: Neidlein Richard , Greulich Peter 
Published: December 2004

AbstractSyntheses of Phosphonic‐ and Phosphinic Analogues of Pantothenic Acid Ethyl Ester and of the Phosphonic Analogue of PantetheineThe replacement of amino acids in peptides by phosphono‐analogous (aminoalkyl)phosphonic acids 1, (2‐aminoethyl)phosphonic acid (2) and substituted derivatives has been an important aspect of peptides research in the last years. In pantothenic acid (3), there is a peptide linkage between (2R)‐2,4‐dihydroxy‐3,3‐dimethylbutyric acid and the amino group of β‐alanine, and in pantetheine (4), there is a second peptide linkage between the β‐alanine and cysteamine. The synthesis of phosphono and phosphino analogues of pantothenic acid ethyl ester, where the β‐alanine is replaced by the diethyl ester of (2‐aminoethyl)phosphonic acid and the ethyl ester of (2‐aminoethyl)methylphosphonic acid, respectively, and the syntheses of the phosphono analogue of pantetheine, where the β‐alanine is replaced by (2‐aminoethyl)phosphonic acid, are described.
(o ‐Hydroxyphenyl)methylphosphonic Acids: Spectrophotometric determination of their pKa values and of the deprotonation sequence
Authors: Chafaa Salah , Meullemeestre Jean , Schwing Marie‐José , Vierling François , Böhmer Volker , Vogt Walter 
Published: December 2004

AbstractUV/VIS Absorption spectra of nitrosubsituted (o‐hydroxyphenyl)methylphosphonic acids (o‐(phosphonomethyl)phenols) were measured as a function of pH at 25° in 0.1M NaClo4 solutions. Computational treatment of the whole set of optical density data between 200 and 500 nm resulted in the determination of the dissociation constants of these polyacids and also of the individual electronic spectra of all the species involved in the deprotonation sequence. The spectral behavior gives information on the structure of the anions formed and consequently the order of the subsequent deprotonation steps could be deduced. For the (2‐hydroxy‐3‐nitro(or 5‐nitro)phenyl)methylphosphonic acid and the 2‐hydroxy‐5‐nitro‐1,3‐phenylenebis(methylphosphonic acid), the phenolic proton dissociates in the last step, while, in the case of (2‐hydroxy‐3,5‐dinitrophenyl)methylphosphonic acid, the last dissociating proton comes from a POH group. An intermediate situation is found for (3‐chloro‐2‐hydroxy‐5‐nitrophenyl)methylphosphonic acid. Generally, the deprotonation sequence is governed by intramolecular H‐bonds involving the phenolic OH group.
Definitive Proof for the Operation of Isotopically Sensitive Branching (‘Metabolic Switching’) in FeI‐Mediated CH Bond Activation in the Gas Phase Short Communication
Authors: Seemeyer Katrin , Prüsse Tilmann , Schwarz Helmut 
Published: December 2004

AbstractRigorous regio‐ and stereospecific labeling experiments are performed to demonstrate the operation of the previously suggested operation of ‘isotopically sensitive branching’ in FeI‐mediated CH bond activation. For the hexane‐1,6‐diol/Fe+‐complex, it is shown that dehydrogenation involves specifically the central C(3)/C(4) position, and the study of the stereospecifically labeled D,L‐ and meso‐[3,4‐D2]‐isotompomers 1e and 1f demonstrates that dehydrogenation proceedes via two competing pathways (i.e. ‘anti’‐ vs. ‘syn’‐route). The contribution of these routes to the product formation is – due to a kinetic isotope effect – controlled by the relative configuration at the labeled positions C(3)/C(4). For the D,L‐form 1e, we estimate a ratio of 49:1 in favor of the ‘anti’‐route; due to an isotope effect, this ratio drops to 4.3:1 for the meso‐form 1f.
Synthesis and Solvent Effects on the Conformation of Hymenistatin 1
Authors: Konat Robert K. , Mierke Dale F. , Kessler Horst , Kutscher Bernhard , Bernd Michael , Voegeli Rainer 
Published: December 2004

AbstractThe cyclic octapeptide cyclo(‐Pro‐Pro‐Tyr‐Val‐ProLeu‐Ile‐Ile‐) (1), isolated from the Hymeniacidon sponge, was synthesized and examined conformationally using NMR and molecular‐dynamics simulations. Most structural parameters of synthetic 1 are in accord with those reported for the isolated material. Our study indicates some small but significant differences in the assignment of the 1H‐ and 13C‐NMR resonances from those of the natural material. The Conformation was determind in both CHCl3 and DMSO using 1H‐NMR and molecular‐dynamics simulations. Both NOE's and coupling constants were used as experimental restraints during the simulations which utilized explicitly the same solvent as in the NMR study. The differences in the interaction of the solvent with 1 were examined, providing insight into the observed differenced in conformation. The dominant conformation contains a ßVIa turn about Ile8‐Tyr3 including a Pro1‐Pro2 cis‐peptide bond and a ßI or ßII turn about Val4‐Ile7 in CHCl3 and DMSO, respectively.
Approaches to the Synthesis of Cytochalasans. Part 11. Further transformations and cyclization attempts directed towards proxiphomin
Authors: Boutellier Markus , Wallach Daniel , Tamm Christoph 
Published: December 2004

AbstractStarting from iodoalcohol 9, the monoprotected dialdehyde 5 was synthesized (Scheme 2) and converted to 17 by reaction with oxo‐phosphonate 15 (Scheme 3). The latter was prepared from 13. Cyclisation of 17 to the target compound 18 failed. Also the attachment of thiol 22 to lactone 19 was unsatisfactory (Scheme 4). Therefore, the building blocks 28 and 29 were synthesized using diene 33 and diester 30 as starting material for 28 and 9 for 29 (Scheme 5 and 6). Hydroxy acid 28 was converted into formyl‐ester 46 (Scheme 7). However, the condensation of its derivatives 48 and 49 with ‘Umpolung’ of the carbonyl reactivity was unsuccessful, probably due to steric hindrance.
The Terpenoids of Maytenus boaria MOL. (Celastraceae)
Authors: Muñoz Orlando , Ruiz Roberto , Gonzáles Antonio , Nüñez Mercedes P. , Jiménez Ignacio , Ravelo Angel 
Published: December 2004

AbstractThe known triterpenoids β‐amyrin (= olean‐12‐en‐3β‐ol; 22), lupeol (= lup‐20(29)‐en‐3β‐ol; 17), betulin (= lup‐20(29)‐ene‐3β,28‐diol; 18), lup‐20(29)‐ene‐3β,30‐diol (20), oleanolic acid (= 3β‐hydroxyolean‐12‐en‐28‐oic acid; 21), and betulonic acid (= 3‐oxolup‐20(29)‐en‐28‐oic acid; 19), together with epicatechol (= cis‐2‐(3,4‐dihydroxyphenyl)‐3,4‐dihydro‐2H‐1‐benzopyran‐3,5,7‐triol; 23), 5′‐O‐methylgallocatechol (= trans‐2‐(3,4‐dihydroxy‐5‐methoxyphenyl)‐3,4‐dihydro‐2H‐1‐benzopyran‐3,5,7‐triol; 24), and 4‐hydroxybenzaldehyde were isolated from the aerial parts of Maytenus boaria (MOL.). Additonally, the eight 4,C4‐dihydro‐β‐agarofuran sesquiterpenoids 1–8, one of them a diol with a (4R)‐configuration, and compound 9 were present in the extract. The structures of these compounds were established by spectroscopic and chemical means.
3‐(Acylamino)‐3‐amino‐2‐nitroacrylonitriles from N‐Acyl‐S‐methyl‐3,3‐diamino‐2‐nitroacrylthioimidates
Authors: Trimiño María I. García , Linden Anthony , Heimgartner Heinz , Cabrera Arturo Macías 
Published: December 2004

AbstractReaction of N‐acyl‐3,3‐diamino‐2‐nitroacrylthioamides 1 with MeI at room temperature leads to N‐acyl‐S‐methyl‐3,3‐diamino‐2‐nitroacrylthioimidates 2 in moderate yields. The latter react with Hg(OAc)2 in DMF yielding 3‐(acylamino)‐3‐amino‐2‐nitroacrylonitriles 8. The structures of 2a and 8a were established by X‐ray crystallography.
Nucleotides Part XL. Synthesis and Characterization of Modified 2′–5′ Adenylate Trimers–Potential Antiviral Agents
Authors: Schirmeister Helga , Pfleiderer Wolfgang 
Published: December 2004

Abstract2′–5′ Adenylate trimers 41–44 carrying the (tert‐butyl)dimethylsilyl (tbds) group at the 3′‐OH position of various sugar moieties were synthesized via the phosphoramidite method. The use of the (tert‐butyloxy)carbonyl (boc) and 2‐(4‐nitrophenyl)ethylsulfonyl (npes) groups for 2′‐OH protection in neighbourhood to the 3′‐O‐tbds residue was compared during the synthesis of the target trimers. For other functional positions, the use of the 2‐(4‐nitrophenyl)ethyl (npe) and 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) blocking groups were favoured.
Nitrostyrene Derivatives of Adenosine 5′‐Glutarates Modified with an Alkyl Spacer and their inhibitory activity on epidermal growth factor receptor protein tyrosine kinase
Authors: Peterli Stefan , Hubmann Dieter , Séquin Urs , Mett Helmut , Traxler Peter 
Published: December 2004

Abstractβ‐Nitrostyrene derivatives of adenosine 5′‐glutarates are potent and selective bisubstrate‐type inhibitors of the epidermal growth factor receptor protein tyrosine kinase (EGF‐R PTK). In an attempt to improve the inhibitory activity, this type of compounds was modified with alkyl spacers of varying length between the nitrostyrene and the glutaryl units. The spacers consisted of 1, 3, 4, and 5 atoms to give compounds of the benzyl, oxyethyl, oxypropyl, and oxybutyl series, respectively (Schemes 1 and 2). Adenosine 5′‐esters were prepared in the benzyl and oxypropyl series only. Compared to the compounds in the parent series without spacer (IC50 = 0.7–12 μM), most of the modified compounds inhibited the EGF‐R PTK only marginally or were inactive (IC50 ≥ 100 μM). The only exceptions were the free acids 19 and 20 with IC50 values of ca. 5 μM. It is noteworthy that esterification of these two hydrogen glutarates with either MeOH or adenosine yielded inactive compounds, which is in contrast to the corresponding substances without spacers.
Crystal Structure of (−)‐Corycavinium (+)‐10‐Camphorsulfonate, a biosynthetic intermediate to hexahydrobenzo[c]phenanthridine alkaloids
Authors: Kamigauchi Miyoko , Noda Yuko , Iwasa Kinuko , Nishijo Zjujiro , Ishida Toshimasa , In Yasuko , Wiegrebe Wolfgang 
Published: December 2004

AbstractThe crystal structure of (−)‐corycavinium (+)‐10‐camphorsulfonate has been investigated by X‐ray analysis. The structure of (−)‐corycavinium ion (  (−)‐(7S,13S,14R)‐5,6,13,13a‐tetrahydro‐13a‐hydroxy‐7‐methyl‐2,3;9,10‐bis(methylenedioxy)‐8H‐dibenzo[a,g]quinolizinium), has been determined. The conformation with B/C‐cis‐conjunction, a twisted half‐chair of ring B, and a half‐chair of ring C, as well as α‐oriented substituted groups N…Me, C…Me, and C…OH is revealed. Feeding experiments with cell suspension cultures of Corydalis incisa (Papaveraceae) defined the intermediacy of (−)‐corycavinium in the route from protoberberine‐type to hexahydrobenzo[c]phenanthridine‐type of alkaloids. On the basis of the present crystal conformation, the stereospecificity of the relating enzyme is biogenetically considered.
Synthesis and NMR Spectroscopic Investigation of a Macrocyclic Diphosphine Ligand and its nickel(II) and palladium(II) complexes
Authors: Widhalm Michael , Kalchhauser Hermann , Kählig Hanspeter 
Published: December 2004

AbstractThe preparation of a macrocyclic diphosphine ligand 5 incorporating a binaphthyl unit and its NiII and PdII complexes, 6 and 7, is described. A complete assignment of 1H,‐ 13C‐, and 31P‐NMR data on the basis of 2D NMR spectroscopy (1H, 1H‐, 13C, 1H‐, 31P, 1H‐, 31P, 13C‐COSY) was possible for 5, and also – in part – for 6 and 7.
Umsetzung von Di(tert‐butyl)‐ und Diphenyldiazomethan mit 1,3‐Thiazol‐5(4H)‐thionen: Isolierung und Kristallstruktur des primären Cycloadduktes
Authors: Mlostoń Grzegorz , Petit Mireille , Linden Anthony , Heimgartner Heinz 
Published: December 2004

Reaction of Di(tert‐butyl)‐ and Diphenyldiazomethane and 1,3‐Thiazole‐5(4H)‐thiones: Isolation and Crystal Structure of the Primary CycloadductReactions of diazo compounds with CS bonds proceed via the formation of thiocarbonyl ylides, which, under the reaction conditions, undergo either 1,3‐dipolar cycloadditions or electrocyclic ring closer to thiiranes (Scheme 1). With the sterically hindered di(tert‐butyl)diazomethane (2c), 1,3‐thiazole‐5(4H)‐thiones 1 react to give spirocyclic 2,5‐dihydro‐1,3,4‐thiadiazoles 3 (Scheme 2). These adducts are stable in solution at −20°, and they could be isolated in crystalline form. The structure of 3c was established by X‐ray crystallography. In CDCl3 solution at room temperature, a cycloreversion occurs, and the adducts of type 3 are in an equilibrium with 1 and 2c. In contrast, the reaction of 1 with diphenyldiazomethane (2d) gave spirocyclic thiiranes 4 as the only product in high yield (Scheme 3). The crystal structure of 4b was also determined by X‐ray analysis. The desulfurization of compounds 4 to 4,5‐dihydro‐5‐(diphenylmethylidene)‐1,3‐thiazoles 5 was achieved by treating 4 with triphenylphosphine in boiling THF. The crystal structure of 5f is shown.