bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparative Study of Platinum Di (t‐butyl) (15N2)diimine and trans‐[(PtCl2(N‐ligand)PBu3)] complexes by 195Pt‐, 31P‐ and 15N‐NMR
Authors: van der Poel Henk , van Koten Gerard , Grove David M. , Pregosin Paul S. , Starzewski Karl A. Ostoja
Published: December 2004

195Pt‐, 31P‐ and 15N‐NMR. data are presented for [PtCl2 (t‐Bu 15NCHCH15N (t‐Bu)) (η2‐styrene)] (1), trans‐[{PtCl2 (PBu3)}2 (t‐Bu 15NCHCH15N (t‐Bu))] (2), trans‐[PtCl2 (t‐Bu 15NCHCH15N (t‐Bu)) (PBu3)] (3) and various complexes of the type trans‐[PtCl2 (N‐ligand) (PBu3)]. In solution the gross structural features of 1 and 2 are shown to be in agreement with those found in the solid state; namely, 1 contains five‐coordinate Pt and 2 is dinuclear. In 3 Pt is four‐coordinate with only one N‐atom of the diimine ligand being coordinated at −50° in CD2Cl2. The NMR. data for 2 and 3 are compared with those of trans‐[PtCl2 (N‐ligand) (PBu3)] (N‐ligand = pyridine, 2, 6‐dimethylpyridine, (15N)‐hexylamine, (15N)‐t‐butylamine and (15N)‐aniline) and are discussed in terms of the donor and acceptor properties of the N‐ligands.
Synthese von diastereo‐ und enantio‐selektiv deuterierten β,ε‐, β,β‐, β,γ‐ und γ,γ‐Carotinen
Authors: Märki Hans Peter , Eugster Conrad Hans
Published: December 2004

Synthesis of Diastereo‐ and Enantioselectively Deuterated β,ε‐, β,β‐, β,γ‐ and γ,γ‐Carotenes

We describe the synthesis of (1′R, 6′S)‐[16′, 16′, 16′‐2H3]‐β, εcarotene, (1R, 1′R)‐[16, 16, 16, 16′, 16′, 16′‐2H6]‐β, β‐carotene, (1′R, 6′S)‐[16′, 16′, 16′‐2H3]‐γ, γ‐carotene and (1R, 1′R, 6S, 6′S)‐[16, 16, 16, 16′, 16′, 16′‐2H6]‐γ, γ‐carotene by a multistep degradation of (4R, 5S, 10S)‐[18, 18, 18‐2H3]‐didehydroabietane to optically active deuterated β‐, ε‐ and γ‐C11‐endgroups and subsequent building up according to schemes \documentclass{article}\pagestyle{empty}\begin{document}${\rm C}_{11} \to {\rm C}_{14}^{C_{\mathop {26}\limits_ \to }} \to {\rm C}_{40} $\end{document} and C11 → C14; C14+C12+C14→C40.

NMR.‐ and chiroptical data allow the identification of the geminal methyl groups in all these compounds. The optical activity of all‐(E)‐[2H6]‐β,β‐carotene, which is solely due to the isotopically different substituent not directly attached to the chiral centres, is demonstrated by a significant CD.‐effect at low temperature. Therefore, if an enzymatic cyclization of [17, 17, 17, 17′, 17′, 17′‐2H6]lycopine can be achieved, the steric course of the cyclization step would be derivable from NMR.‐ and CD.‐spectra with very small samples of the isolated cyclic carotenes. A general scheme for the possible course of the cyclization steps is presented.
Structure‐Activity Relationships of Oxygenated Morphinans. I. 4‐Mono‐ and 3,4‐dimethoxy‐N‐methylmorphinans and ‐N‐methyl‐morphinan‐6‐ones with unusually high antinociceptive potency. Preliminary communication
Authors: Jacobson Arthur E. , Hsu Fu‐Lian , Rozwadowska Maria D. , Schmidhammer Helmut , Atwell Louise , Brossi Arnold , Medzihradsky Fedor
Published: December 2004

The antinociceptive potency and receptor affinity of several optically active aromatic mono‐ and di‐oxygenated N‐methylmorphinans and N‐methylmorphinan‐6‐ones, prepared from natural morphine, were determined. Thus, in order of antinociceptive potency, 4‐methoxy‐N‐methylmorphinan‐6‐one ≈ 3,4‐dimethoxy‐N‐methylmorphinan‐6‐one ≈ 3,4‐dimethoxy‐N‐methylmorphinan > 4‐methoxy‐N‐methylmorphinan ≈ 4‐acetoxy‐N‐methylmorphinan‐6‐one > 4‐acetoxy‐N‐methylmorphinan ≈ 4‐hydroxy‐N‐methylmorphinan‐6‐one ≈ 4‐hydroxy‐N‐methylmorphinan. The 4‐hydroxy compounds were slightly less potent than morphine, and the 4‐methoxy and 3,4‐dimethoxy compounds were found to have three times the potency of morphine. 4‐Methoxy‐N‐methylmorphinan‐6‐one showed an opiate receptor affinity one‐third that of morphine; this is a remarkably high affinity for a non‐phenolic compound.
Bestimmung der Chiralität optisch aktiver Nickelkomplexe mit porphinoidem Ligandysystem
Authors: Meier Kurt , Scheffold Rolf , Engel Peter
Published: December 2004

Determination of the Chirality of Optically Active Porphine Type Nickel Complexes

The chirality of (+)‐[1‐methyl‐8 H‐HDP]nickelperchlorate (4) was determined to be (1R) by X‐ray analysis of 7a combined with chemical correlation of the chirality at C(1′) of the 1′‐methyl‐2′‐oxopropoxy side chain of 7a with (−)‐(R)‐2‐methyl‐2,3‐butandiol (9).
Enantioselektive Reaktionen an porphinoiden Nickelkomplexen
Authors: Meier Kurt , Scheffold Rolf
Published: December 2004

Enantioselective Reactions on Porphine Type Nickel Complexes

The thermodynamically controlled addition of alcohols to (+)‐(1R)‐[1‐methyl‐8H‐HDP]nickelperchlorate (1; e.e. 92%) yields exclusively the corresponding cis‐1,11‐disubstituted porphinoids. Chemical transformation of functional groups in the alkoxy side‐chain of the chiral addition product followed by acid catalyzed elimination yields the derived alcohols and 1. By this procedure, the following enantioselective transformations were studied: methylation of meso‐2,3‐butandiol (5) to (+)‐(2R,3S)‐3‐methoxy‐2‐butanol (8a; e.e. 87%), diimide reduction of 2‐ethylallyl alcohol (9) to (+)‐(2R)‐2‐methyl‐1‐butanol (12a; e.e. 15%), and hydride reduction of 4‐hydroxy‐2‐butanone (13) to (+)‐(3S)‐1,3‐butandiol (16a; e.e. 20%). Addition of 2,2‐dimethyl‐1,3‐propandiol (17) to 4, followed by esterification of the free hydroxy group with trifluoromethanesulfonic anhydride and solvolysis of the sulfonate 19 yielded a bridged complex with unrearranged alkyl chain for which structure 20 is proposed.
Notiz zum massenspektrometrischen Zerfall monohalogenierter Essigsäuren und Essigsäureester. 36. Mitteilung über massenspektrometrische Untersuchungen
Authors: Lorenzi‐Riatsch Annalaura , Bild Norbert , Hesse Manfred
Published: December 2004

Note on the Mass Spectral Decomposition of Monohalogenated Acetic Acids and its Esters

Besides the well known ester fragmentation reactions two unusual decomposition reactions are observed in the mass spectra of the title compounds, leading to the ions [M‐CO2]+ and [M‐HX]+. The rearrangement reactions involved in the formation of these ions are discussed.
Mechanisms of Diazo Coupling Reactions. Part XXXI. Aminoazo formation in the diazo coupling of N, N‐dimethylaniline and m‐toluidine with p‐methoxybenzenediazonium tetrafluoroborate in acetonitrile
Authors: Penton John R. , Zollinger Heinrich
Published: December 2004

In the title reactions it is shown that aminoazo formation does not occur by direct attack of diazonium ion at C‐atom. Initial attack is at N‐atom, but proton loss from the ωN‐complex formed is relatively slow. Hence, at low amine concentration this rearranges intermolecularly to the aminoazo derivative. At high amine concentration a second method of aminoazo formation can take place involving attack of an amine molecule on the ωN‐complex or on a molecular complex formed between the diazonium ion and the amine. Implication of these proposals for the diazoamino rearrangement are discussed.
Photochemische Reaktionen 122. Mitteilung [1]. Zur vinylogen β‐spaltung von epoxy‐enonen: Photoisomerisierung des 3,4:5,6‐diepoxy‐5,6‐dihydro‐β‐jonons
Authors: Bischofberger Norbert , De Weck Guy , Frei Bruno , Wolf Hans Richard , Jeger Oskar
Published: December 2004

Vinylogous β‐Cleavage of Epoxy‐enones: Photoisomerization of 3,4: 5,6‐Diepoxy‐5,6‐dihydro‐β‐ionone

On 1n,π*‐excitation (λ>347 nm), 3,4:5,6‐diepoxy‐5,6‐dihydro‐β‐ionone ((E)‐3) shows the typical behaviour of α,β‐unsaturated γ,δ‐epoxy ketones furnishing the (Z)‐enone 3 and by C(γ),O cleavage of the oxirane the dihydrofuryl ketone 10 and the cyclohexanones (E/Z)‐11. However, on 1π,π*‐excitation an unexpected type of transformation is observed: (E)‐3 is isomerized to the four aliphatic triketones 5–8 as the main products. To a smaller extent the allene diketone 9 is formed by a known type of isomerization as well as (Z)‐3.

As the starting material for the preparation of (E)‐3, the known epidioxy‐enone (E)‐4 was used. In addition to (E)‐3, (E)‐4 gives the aliphatic triketone 6 and the hydroxyenone 15 by thermal or catalytic isomerization.
Temperaturabhängiger Circulardichroismus von (3S, 3′R)‐ und (3S, 3′ S)‐Adonixanthin
Authors: Noack Klaus
Published: December 2004

The temperature dependent CD. spectra of (3S, 3′R)‐ and (3S, 3′S)‐adonixanthin are compared with those of (3R, 3′R)‐zeaxanthin (1) and (3S, 3′S)‐astaxanthin (2). The room temperature spectra of 1 and 2 are quite similar. On cooling to −180° the CD. of 1 simply intensifies, the CD. of 2 changes sign and becomes also very intense. The room‐temperature CD. of (3S, 3′R)‐adonixanthin (3) resembles closely those of 1 and 2 at room temperature. On cooling, however, it becomes weak and changes strongly its shape. With (3S, 3′S)‐adonixanthin (4) it is the low‐temperature spectrum which resembles that of 2 at low temperature, whereas the room‐temperature spectrum is weak and quite different in shape. These observations can be explained with temperature dependent equilibria where the end groups are twisted out of the plain of the chain thereby conferring chirality to the conjugated system.
Substituted 2‐Phenylnaphthalenes, a New Class of Nematic Liquid Crystals. Preliminary communication
Authors: Lauk Urs , Skrabal Peter , Zollinger Heinrich
Published: December 2004

Eleven representatives of 6‐n‐alkoxy‐ and 6‐n‐alkanoyloxy‐2‐(4′‐cyanophenyl)‐naphthalenes, a new class of nematogens, are described.
Eine ergiebige Herstellung von 1α,3β‐Dihydroxy‐Δ5‐steroiden durch Reduktion von 1α,2α‐Epoxy‐4,6‐dien‐3‐onen mit Lithium in Ammoniak
Authors: Fürst Andor , Labler Ludvik , Meier Werner
Published: December 2004

An Efficient Procedure for Preparing 1α,3β‐Dihydroxy‐Δ5‐steroids by Reduction of 1α,2α‐Epoxy‐4,6‐dien‐3‐ones with Lithium in Ammonia

A number of 1α,3β‐dihydroxy‐Δ5‐steroids of the cholestane, (20S)‐20‐methyl‐pregnane (23,24‐dinorcholane), pregnane and androstane series were synthesized from common steroidal precursors. A process originally reported by Barton et al., based on 1,4,6‐trien‐3‐ones as intermediates, was used for the introduction of the 1α‐hydroxyl function. The last step of this process, consisting of lithium/ammonia reduction of 1α,2α‐epoxy‐4,6‐dien‐3‐ones, was found to be crucial and therefore subjected to particular study. A reproducible procedure permitting high‐yield conversion was developed. It consists of first reducing the epoxydienone with an approximately stoichiometric amount of lithium in ammonia to give, after protonation with ammonium chloride, a 1α‐hydroxy‐5‐en‐3‐one. This intermediate is then further reduced by repeated alternating treatment with ammonium chloride and an equivalent amount of lithium.
Etude par des techniques de partition d'énergie des facteurs qui conditionnent l'équilibre conformationnel de propènes disubstitués‐1,3 de configuration E
Authors: Nguyen‐Xuan Tho , Tronchet Jean M. J. , Bill Hans
Published: December 2004

Effects of the Nature of the C(1) Substituent on the Conformational Equilibrium of (E)‐derivatives of 3‐Methoxypropene: Determination of the origin of the phenomenon using energy partitioning techniques

Intermolecular interactions taking place in the compounds of the general formula (E)‐CH3OCH2CHCHX were analyzed in terms of one‐ and two‐center interaction energies within the framework of SCF ab initio (STO‐3G), Extended Hückel and CNDO methods. The results confirmed the important role of unoccupied orbitals in the stabilization of the different conformers.
Laser‐Induced Fluorescence and Photoelectron‐Photon Coincidence Studies of 3,5‐Octadiyne Cation
Authors: Maier John P. , Misev Liubomir , Thommen Fritz
Published: December 2004

3,5‐Octadiyne cation in its lowest excited state has been studied in the gas phase by laser‐induced fluorescence and photoelectron‐photon coincidence techniques. The excitation spectrum of the Ã2″←2A″ transition has been obtained and yields vibrational frequencies of some of the fundamentals for the excited cationic state. The fluorescence quantum yields and lifetimes at selected energies within the Ã2A″ state have been determined from the coincidence measurements. This provides quantitative data for the discussion of the relaxation behaviour of such an excited open‐shell cation.
3‐Triethylsilyloxypentadienyllithium, a Versatile 1,3‐Diene‐ or Vinyl Ketone‐Building Block
Authors: Oppolzer Wolfgang , Snowden Roger L. , Simmons Dana P.
Published: December 2004

Deprotonation of the 3‐trialkylsilyloxy‐1,4‐diene 3a and subsequent electrophilic substitution of the non‐isolated 3‐trialkylsilyoxypentadienyllithium 4 gives the α‐ and γ‐products 8 and/or 6 in good yields. Whereas alkylation of 4 proceeds with variable regioselectivity (Table 1) aldehydes and ketones attack preferentially the γ‐position of 4 (Table 2). The desired γ‐products 6 may be directly subjected to inter‐ and intramolecular [4 + 2]‐additions as demonstrated by the reactions 5a ( 6d) → 7 and 6h → 19 (Schemes 4 and 12). Alternatively, smooth fluoride‐promoted silylether‐cleavage 6 → 11 (Scheme 8) provides a convenient approach to substituted vinyl ketones such as to the natural products 11f (Table 3). The stereoselective conversion 6k → 23 (Scheme 13) implies an endo‐selective intramolecular Diels‐Alder addition (26 → 23) and exemplifies the use of 4 as an equivalent of the hypothetical anion IV. Furthermore, some electrophilic substitutions of the hexadienyllithium 15 have been studied (Scheme 10).
Synthesis and Biological Properties of Enkephalin‐like Peptides Containing Carboranylalanine in Place of Phenylalanine
Authors: Schwyzer Robert , Do Kim Quang , Eberle Alex N. , Fauchére Jean‐Luc
Published: December 2004

The syntheses of [D‐Ala2, Car4, Leu5]‐enkephalin, its amide, and of [D‐Ala2, Car4, Met5]‐enkephalin amide are described in detail. The three compounds show pronounced morphine‐like potencies in certain bio‐assays, and were used to investigate the influence of electronic, steric and hydrophobic properties of the side‐chains of amino acids no. 4 and 5 on opioid activity (see [13]).
Bestimmung des Enantiomerenüberschusses von chiralen Ammonium‐Ionen mit Hilfe von Flüssigmembranelektroden
Authors: Bussmann Walter , Simon Wilhelm
Published: December 2004

Determination of the Enantiomeric Excess of Chiral Ammonium long Using Liquid Membrane Electrodes

A cell assembly with two membranes each containing one enantiomer of a chiral ionophore is described. It is suitable for the direct potentiometric determination of the enantiomeric excess of ions. The method is used to determine the enantiomeric excess of ephedronium ions in aqueous solutions.
Alkali Metal/Ammonia Reductions of Ketones Should Be Run in the Presence of Ammonium Ion
Authors: Rautenstrauch Valentin , Willhalm Bruno , Thommen Walter , Burger Ulrich
Published: December 2004

Reduction of (+)‐[3,3−2H2]camphor ([3,3−2H2]1) with lithium, sodium or potassium in ammonia and a co‐solvent gave; 1) the enolate of [3,3−2H2]1 and the alcoholates of (−)‐[2,3,3−2H3]isoborneol ([2,3,3−2H3] and (+)‐[2,3,3−2H3]borneol ([2,3,3−2H3]3); 2) the alcoholates of [3,3−2H2]2 and [3,3−2H2]3; 3) the dialcoholates of the pinacols [3,3,3′,3′−2H4]4 and [3,3,3′,3′−2H4]5. It is proposed that these are formed from the ketyls [3,3−2H2]1‐ M+, by: 1) disproportionation; 2) H‐atom abstraction from the medium; 3) dimerization. Protonation upon work‐up afforded [endo−32H]1, [2,3,3−2H3]2, [2,3,3−2H3]3,[3,3−2H2]2, [3,3−2H2]3, [3,3,3′,3′−2H4]4 and [3,3,3′,3′−2H4]5. Pinacol [3,3,3′,3′−2H4]5 was the main and pinacol [3,3,3′,3′−2H4]4 a minor product in the reductions with lithium and both were minor products in the reductions with sodium; pinacols were not formed in the reductions with potassium. Parallel reductions of 1, unlabeled, analogously led to 2, 3, 4 and 5, and the ratios 2/3 differed from the ratios ([2,3,3−2H3]2+[3,3−2H2] 2/([2,3,3−2H3]+[3,3−2H2]3) under certain conditions. Different values for these ratios were found in the reductions with each metal, all of which corresponded to low overall diastereoselectivities. Reactions 1 and 3 persisted when the reductions were carried out in ammonia/water/co‐solvent mixtures and the enolate formed via reaction 1 was protonated and the resulting [endo‐3‐2H]1 recycled. Reaction 2 cannot be monitored under these conditions. Reactions 1 and 3, and by inference also reaction 2, were almost completely suppressed when analogous reductions were carried out in the presence of ammonium chloride, [3,3−2H2]2 and [3,3−2H2]3 being obtained almost exclusively, in a 6: 94 ratio. It is proposed that the mechanism outlined in House [1] was dominant when, and only when, ammonium ion was the proton source; it may have competed when water was the proton source.
The Electrochemical Measurement of Rate Constants for the Catalyzed Oxidation and Reduction of Water in microheterogeneous systems
Authors: Sutcliff Emile , Neumann‐Spallart Michael
Published: December 2004

The appearent first‐order rate constants for the oxidation of water by iron tris (bipyridyl) (Fe (bpy)3+3), and reduction of water by methylviologen (MV+) catalyzed by a stabilized RuO2 or Pt‐sol, respectively, were measured. Rate constants for water oxidation at pH 7 of 0.4 s−1 and water reduction at pH 4.7 and pH 1 of up to 460 s−1 for different sols were found.
EPR. Spectroscopic Investigations of Planar Cu (II)‐ and Low‐Spin Co (II)‐Complexes in Nematic Phases and in Single Crystals
Authors: von Zelewsky Alex , Zobrist Markus
Published: December 2004

EPR. spectra of planar low‐spin Co (II)‐ and Cu (II)‐complexes were obtained in oriented nematic phases, and compared with single crystal measurements. Unambiguous directional information is only obtained in the case of solute molecules in which the two in‐plane axes are of distinctly different length.
Fragmentation of Homoallylic Alkoxides. Thermolysis of potassium 2‐substituted bicyclo [2.2.2]oct‐5‐en‐2‐alkoxides
Authors: Snowden Roger L. , Schulte‐Elte Karl H.
Published: December 2004

Thermolysis of the potassium 2‐substituted bicyclo [2.2.2]oct‐5‐en‐2‐alkoxides derived from alcohols 2–17 at 90–120° in hexamethylphosphoric triamide affords unsaturated ketones resulting from allylic bond cleavage. The mechanistic and synthetic aspects of this anionic fragmentation are discussed with reference to the formation of 1‐(3′‐cyclohexenyl)‐2‐alkanones 18–28 via initial heterolytic C(1), C(2)‐bond cleavage in the substrate alkoxide and regioselective, intramolecular protonation of the resultant transient allylic anion.
Synthesis of Phenyl‐ and Benzyl‐Substituted Pyrrolidines and of a Piperidine by Intramolecular C‐Alkylation. Synthons for tricyclic skeletons
Authors: Achini Roland
Published: December 2004

The construction of new or novelly functionalized annulated and bridged tricylic compounds by two consecutive C,C‐bond formations (a and b in la, Scheme 1) is described. In a first step, chloroalkyl‐substituted aminonitriles yielded pyrrolidines 8, 15a, 15b, 23, 25 and piperidine 18 by carbanionic ring closure (Schemes 5, 6, 7 and 8). Subsequent Friedel‐Crafts cyclization transformed the β‐aminonitriles 8, 15a, 15b, and 18 either directly or via their carboxylic acid derivatives to the indeno [1, 2‐c]pyrrole, 2, 5‐methano‐3‐benzazocine, benz [f]isoindoline and 1, 4‐ethano‐2‐benzazapine skeletons 11, 16a, 16b and 21, respectively (Schemes 5, 6 and 7). By classical ring expansion reactions the pyrrolo [3, 4‐c]isoquinoline and benzopyrano‐[3, 4‐c]pyrrole skeletons 28 resp. 31 were obtained from 11 (Scheme 9).
Reaktivität und Elektronenstruktur porphinoider Nickelkomplexe
Authors: Meier Kurt , Scheffold Rolf , Calzaferri Gion
Published: December 2004

Reactivity and Electronic Structure of Porphine‐type Nickel Complexes

The electronic structure of the porphine‐type hexaaza[16]annulene‐nickel dikation 1′ as well as its mono‐ and diaddition products 2′ and 3′ (Scheme 2) has been considered by an extended Hückel treatment (SCCC‐MO including charge iteration on the central metal atom). Correlations between calculated data and reactivity of the porphinoid compounds 1, 2 and 3 (Scheme 1) are discussed.
Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6‐Oxo‐isophoron. III. Ein neues Konzept für die Synthese der enantiomeren Astaxanthine
Authors: Zell Reinhard , Widmer Erich , Lukáč Teodor , Leuenberger Hans Georg Wilhelm , Schönholzer Peter , Broger Emil A.
Published: December 2004

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophorone. III. A New Concept for the Synthesis of the Enantiomeric Astaxanthins

A new and efficient concept for the total synthesis of (3S, 3'S)‐ and (3R, 3'R)‐astaxanthin (1a and 1c, resp.) in high overall yield and up to 99,2% enantiomeric purity is described. Key intermediates are the (S)‐ and (R)‐acetals 10 and 17, respectively (Scheme 2). These chiral building blocks were synthesized via three different routes: a) functionalization of the enantiomeric 3‐hydroxy‐6‐oxo‐isophorons4) 2 and 11, respectively (Scheme 2); b) optical resolution of 3,4‐dihydroxy‐compound4) 19 (Scheme 3), and c) fermentative reductions of 6‐oxo‐isophorone derivatives (Schemes 4 and 5). ‐ The absolute configurations of the two intermediates 12 and 13 (Scheme 2) have been confirmed by X‐ray analysis. ‐ The final steps leading to the enantiomeric astaxanthins are identical with those described for optically inactive astaxanthin [1].
Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6‐Oxo‐isophoron. IV. Neues Konzept für die Synthese von (3RS, 3′RS)‐, (3S, 3′S)‐ und (3R, 3′R)‐9,9′‐dicis‐7,8,7′,8′‐Tetradehydroastaxanthin
Authors: Zell Reinhard , Widmer Erich
Published: December 2004

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophorone. IV. A Novel Concept for the Synthesis of (3RS, 3′RS)‐, (3S, 3′S)‐ and (3R, 3′R)‐9,9′‐dicis‐7,8,7′,8′‐Tetradehydroastaxanthin

Starting from readily available intermediates of the synthesis of astaxanthin, (3RS, 3′RS)‐, (3R, 3′R)‐ and (3S, 3′S)‐9,9′‐di‐cis‐tetradehydroastaxanthin (1, 1a and 1b, resp.) were synthesized, 1 and 1b for the first time. Key features of this concept are: a) use of the unprotected, acetylenic phosphonium salts 8–12, b) a two‐step synthesis with 47% overall yield, and c) good chemical and optical purity of the end products.
Synthese von optisch aktiven, natürlichen Carotinoiden und strukturell verwandten Naturprodukten. IX. Synthese von (3R)‐Hydroxyechinenon, (3R, 3′R)‐ und (3R, 3′S)‐Adonixanthin, (3R)‐Adonirubin, deren optischen Antipoden und verwandten Verbindungen
Authors: Bernhard Kurt , Englert Gerhard , Mayer Hans , Müller Robert K. , Rüttimann August , Vecchi Max , Widmer Erich , Zell Reinhard
Published: December 2004

Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. IX. Synthesis of (3R)‐Hydroxyechinenone, (3R, 3′R)‐ and (3R, 3′S)‐Adonixanthin, (3R)‐Adonirubin, Their Optical Antipodes and Related Compounds

The synthesis of racemic and optically active hydroxyechinenone (12–14), adonixanthin (16–19), adonirubin (22–24), meso‐astaxanthin (26) and their corresponding diosphenols 15, 20, 21, 25, 27, 28, and 29) by Wittig reaction is reported, starting from suitable C15‐phosphonium salts and C10‐aldehydes.
Enamines. III. A theoretical and photoelectron spectroscopic study of the molecular and electronic structures of aziridine enamines
Authors: Müller Klaus , Previdoli Felix
Published: December 2004

The photoelectron (PE.) spectra of N‐vinylaziridine (1) and some methyl and ethyl substituted derivatives are discussed in the light of quantum‐chemical model calculations using the PRDDO SCF method. All aziridine enamines are found to exist as equilibrium mixtures of variable compositions, with an enamine‐type conformation (I) generally as the major and a trans‐bisected form (II) as the minor component.
The Hydroperoxidation of Olefins by Singlet Oxygen. Validity of the zwitterionic peroxide model
Authors: Jefford Charles W.
Published: December 2004

The regioselectivity of the hydroperoxidation of tetrasubstituted olefins by singlet oxygen is rationalized in terms of the zwitterionic peroxide model.
Tasmanin, ein neues Indolalkaloid aus Aristotelia peduncularis (LABILL.) HOOK. F. 181. Mitteilung über organische Naturstoffe
Authors: Kyburz Rolf , Schöpp Emanuel , Bick I. Ralph C. , Hesse Manfred
Published: December 2004

Another representative of this group of alkaloids, aristoteline (2), was also isolated from A. peduncularis. This natural compound has previously been isolated from A. serrata and A. chilensis.
Synthesis and Diels‐Alder Reactivity of 2,3,5,6‐Tetramethylidenenorbornane
Authors: Pilet Olivier , Vogel Pierre
Published: December 2004

Pd‐catalyzed double carbomethoxylation of the Diels‐Alder adduct of cyclo‐pentadiene and maleic anhydride yielded the methyl norbornane‐2,3‐endo‐5, 6‐exo‐tetracarboxylate (4) which was transformed in three steps into 2,3,5,6‐tetramethyl‐idenenorbornane (1). The cycloaddition of tetracyanoethylene (TCNE) to 1 giving the corresponding monoadduct 7 was 364 times faster (toluene, 25°) than the addition of TCNE to 7 yielding the bis‐adduct 9. Similar reactivity trends were observed for the additions of TCNE to the less reactive 2,3,5,6‐tetramethylidene‐7‐oxanorbornane (2). The following second order rate constants (toluene, 25°) and activation parameters were obtained for: 1 + TCNE → 7: k1 = (255 + 5) 10−4 mol−1 · s−1, ΔH≠ = (12.2 ± 0.5) kcal/mol, ΔS≠ = (−24.8 ± 1.6) eu.; 7 + TCNE → 9, k2 = (0.7 ± 0.02) 10−4 mol−1 · s−1, ΔH≠ = (14.1 ± 1.0) kcal/mol, ΔS≠ = ( −30 ± 3.5) eu.; 2 + TCNE → 8: k1 = (1.5 ± 0.03) 10−4 mol−1 · s−1, ΔH≠ = (14.8 ± 0.7) kcal/mol, ΔS≠ = (−26.4 ± 2.3) eu.; 8 + TCNE → 10; k2 = (0.004 ± 0.0002) 10−4 mol−1 · s−1, ΔH≠ = (17 ± 1.5) kcal/mol, ΔS≠ = (−30 ± 4) eu. The possible origins of the relatively large rate ratios k1/k2 are discussed briefly.
Über Pterinchemie. 79. Mitteilung. 13C‐und 15N‐NMR.‐spektroskopische Untersuchungen an der (6RS)‐5, 10‐Methylen‐5, 6, 7, 8‐tetrahydro‐L‐folsäure; eindeutiger Beweis ihrer Struktur
Authors: Kalbermatten Roger , Städeli Werner , Bieri Jost H. , Viscontini Max
Published: December 2004

13C‐ and 15N‐NMR.‐Spectroscopic Studies on (6RS)‐5, 10‐Methylene‐5, 6, 7, 8‐tetrahydro‐L‐folic Acid; Unequivocal Proof of thier Structure

The existence of a 5, 10‐methylene bridge in the title compound has been established with the help of 15N‐NMR, and 13C‐NMR. spectroscopy. The simultaneous coupling of 13C(11) with 15N(5) and 15N(10) proves that C(11) must be bound as a methylene bridge to both N‐atoms. Some other aspects of the NMR. spectra of the compound are discussed. Synthesis of the title product with the label 15N is described.
Synthese von (−)‐(5R,6S)‐5,6‐Epoxy‐5,6‐dihydro‐β‐ionon
Authors: Acemoglu Murat , Eschenmoser Walter , Eugster Conrad Hans
Published: December 2004

Synthesis of (−)‐(5R,6S)‐5,6‐epoxy‐5,6‐dihydro‐β‐ionone

Optically active 5,6‐epoxy‐5,6‐dihydro‐β‐ionones have been prepared for the first time and their absolute configurations were determined by correlation with (−)‐(S)‐α‐ionone. Acid catalyzed hydrolysis of the epoxide proceeds with retention of the configuration at C(6) and with inversion at C(5).
Dediazoniation of Arenediazonium Ions. Part XIX. Effect of thiocyanate ion in the reactions of 2,4,6‐trimethylbenzenediazonium tetrafluoroborate in 2,2,2‐trifluoroethanol
Authors: Szele Ivanka , Zollinger Heinrich , Deshpande Ashok D.
Published: December 2004

The dediazoniation of 2,4,6‐trimethylbenzenediazonium tetrafluoroborate (1) in 2,2,2‐trifluoroethanol (TFE) was studied in the presence of potassium thiocyanate. The effect of added salt on the dediazoniation rate, the Nα‐Nβ rearrangement (Eqn. 2), the exchange of the 15N‐labelled diazo group with molecular nitrogen (Eqn. 3), and the reaction products was determined. With 0.3M KSCN a dediazoniation‐rate increase of 16.5% was achieved, and the amounts of rearranged and exchanged product were reduced to 88% and 70%, respectively, of the values found in pure TFE. The dediazoniation products formed are ArF (3), ArOCH2CF3 (4), ArSCN (5), ArNCS (6) and traces of 5, 7‐dimethylindazole (7). All the data are in agreement with, and support the previously proposed mechanism (Equ. 1) of heterolytic dediazoniation of arenediazonium salts.
The Radicals and Radical Dianions of Bridged [11]‐ and [15]Annulenyls as Compared with Those of Benzotropyl and 2,3‐Naphthotropyl
Authors: Gerson Fabian , Huber Walter , Müllen Klaus
Published: December 2004

The 1,6‐methano[11]annulenyl (1·), 1,6:8, 14‐propane‐1,3‐diylidene[15]annulenyl (2·), benzotropyl (3·) and 2,3‐naphthotropyl (4·) radicals have been characterized by their ESR. spectra. The corresponding radical dianions, , , and , have also been studied both by ESR. and ENDOR. spectroscopy. Assignment of the coupling constants aHμ to protons in the individual positions μ of these radicals and radical dianions is to a large extent based on investigations of specifically deuteriated derivatives. The radicals 1·, 2·, 3· and 4· exist in temperature‐dependent equilibria with (1)2, (2)2, (3)2 and (4)2, respectively, where (1)2 to (4)2 denote mixtures of dimers of 1· to 4·. The dissociation enthalpies, ΔH°, of (1)2 (102 kJ/mol) and (2)2 (88 kJ/mol) are considerably smaller than those of (3)2 and (4)2 which do not significantly differ from the ΔH° value of bitropyl (139 ± 6 kJ/mol). This finding indicates that the gain in π‐electron delocalization energies, Δ(DE)π, upon dissociation markedly increases on going from bitropyl, (3)2 and (4)2 to (1)2 and (2)2, and thus points to an additional ‘resonance stabilization’ of 1· and 2·, as compared with 3· and 4·. A more pronounced π‐spin localization on the 7‐membered ring is observed in 3·, 4·, and relative to the corresponding species, 1·, 2·, and . It can be interpreted in terms of simple π‐perimeter models without explicitly invoking substantial homoconjugative interactions between the bridged centres in 1·, 2·, and . However, the shortcomings of these crude models do not allow one to make a clear‐cut statement about the contributions of the homotropyl structures to the π‐systems of these paramagnetic species. The radical dianions and exhibit considerable hyperfine splittings from one 23Na or 39K nucleus of the counter‐ion, whereas for and such splittings stem from two equivalent alkali metal nuclei. This finding is readily rationalized by different geometries of the bridged annulenyls and their benzo‐ and naphthotropyl analogues. Hyperfine data are also given for the radical anions of 7 H‐benzocycloheptene, (3‐H)\documentclass{article}\pagestyle{empty}\begin{document}$2^{\ominus \atop \dot{}}$\end{document}, and 6 H‐(2,3‐naphtho)cycloheptene, (4‐H)\documentclass{article}\pagestyle{empty}\begin{document}$2^{\ominus \atop \dot{}}$\end{document}, as well as for the radical dianion of 1,6:8,14‐bismethano[15]annulenyl,5\documentclass{article}\pagestyle{empty}\begin{document}$2^{\ominus \atop \dot{}}$\end{document}.
Relationship between Molecular Properties and Conformation of Chiral Alkanes
Authors: Azzena Ugo , Luisi Pier Luigi , Suter Ulrich W. , Gladiali Serafino
Published: December 2004

Mixtures of the diastereomers of 2,2,3,5,6‐pentamethylheptane were prepared in two ways, either starting with compounds of (3R)‐configuration, or from compounds of (5R)‐configuration. Comparison of the GC. and optical rotatory power of the fractions of these two mixtures permitted the unambiguous assignment of the absolute configuration and molar rotatory power to the various diastereomers ([M] = + 119.1° for the (3R, 5R)‐ and [M] = + 79.8° for the (3R, 5S)‐diastereomer). The very high molar rotatory power which was expected on the basis of the conformational analysis carried out with a rotational‐isomeric‐3‐states model is interpreted as arising from the molecular ‘conformational rigidity’, i.e. from the presence of only few conformers. Conformational properties of these compounds were computed using a new approach, which scans the whole space of each bond (2 π) in 5° steps and calculates the conformational energy based upon semiempirical potential functions. The conformational flexibility of each bond of the two diastereomers is evaluated in terms of the a priori probability density function of that bond. This allows us to analyze in detail how configurational differences affect conformational properties. The molar rotatory power of the two diastereomers as calculated with a new method recently developed in our group is in excellent agreement with experimental data. The molar rotatory power is analyzed in terms of the contribution of the single bonds.
Transition metal ions and amides. VIII. Discrimination between different models for the complexation of Cu2+ with N, N′‐diglycyl 1, 2‐ethanediamine, N, N′‐diglycyl‐1, 3‐propanediamine and glycine ethylamide by potentiometric or by spectrophotometric titration
Authors: Briellmann Markus , Zuberbühler Andreas D.
Published: December 2004

The complexation of Cue2+ with 1, 8‐diamino‐3, 6‐diaza‐2, 7‐octanedione (N, N′‐diglycyl‐1, 2‐ethanediamine, DED) and with 1, 9‐diamino‐3, 7‐diaza‐2, 8nonanedione (N, N′‐diglycyl‐1, 3‐propanediamine, DPD) has been studied by potentiometric and by spectrophotometric titration. With both ligands L the complexation to Cue2+ leads to relatively complicated equilibria with CuLH3+, CuL2+, CuLH−2, and dimeric Cu2L complexes. With DED, another dimeric species, Cu2L2H, is formed in addition. Independent numerical treatment of spectrophotometric and poteritiometric titrations was used to obtain a satisfactory model for the complexation and to test the relative discriminatory power of the two methods. Titrations of glycine ethylamide (GEA) were used as an additional test and as a model for DED and DPD. It was shown that in each case spectrophotometric titrations give results of similar reproducibility and have a discriminatory power equal to or better than potentiometric titrations, provided that optimum mathematical algorithms are used in the numerical treatment.
Mechanisms of Diazo Coupling Reactions. Part XXXII. The Diazoamino Rearrangement in 20% Acetonitrile/Aqueous Buffers
Authors: Kelly Richard P. , Penton John R. , Zollinger Heinrich
Published: December 2004

The rearrangements of 4′‐methoxy‐N‐methyl‐ and N‐methyl‐4′‐nitro‐diatzoaminobenzene have been studied in 20% acetonitrile/aqueous buffers. The reactions are specifically acid catalyzed and involve pre‐equilibrium formation of amine and diazonium salt followed by rate‐limiting attack of the diazonium ion at a C‐atom (C‐coupling) to give the corresponding aminoazo compounds. There is no evidence to suggest that, under the present conditions, mechanisms other than the established Friswell‐Green mechanism occur. The traditional two‐stage synthesis of aminoazo compounds via isolated diazoamino compounds can therefore be replaced by a one stage process for amines which undergo initial attack at a N‐atom by diazonium ion (N‐coupling).
Physico‐chemical properties of deuteriated compounds. 6th Communication. The H/D exchange in mixtures between hydrogen and heptane, methylcyclohexane or cycloheptane over Ni‐catalyst
Authors: Dessauges GÉRald , Gäumann Tino
Published: December 2004

The isotopic exchange between hydrogen and saturated hydrocarbons over Nicatalysts has been studied as a function of temperature and degree of deuteriation. The experimental results can be explained by a model containing four parameters. Two different adsorbed species are assumed: in the ‘alkyl’‐species one H‐atom is exchanged in a single adsorption step; the ‘olefin’‐species exchanges at least two H‐atoms at the same time. Both species can undergo multiple exchange per adsorption step.
Vinylketenes as Synthons for Bicyclo[4.2.1]nonadienones
Authors: Huston Rima , Rey Max , Dreiding André S.
Published: December 2004

Sechs Vinylketene (9a–9f), wovon fünf Chlor‐vinylketene (9a–e) (s. Schema 2), in situ durch 1,4‐Eliminierung von HCI aus den entsprechenden α, β‐ungesättigten Säurechloriden hergestellt, wurden mit Cyclopentadien (2) bzw. 6,6‐Dimethylfulven (3) umgesetzt. Durch [2 + 2]‐Cycloaddition entstanden fünf 7‐vinylsubstituierte Bicyclo[3.2.0]‐2‐hepten‐6‐one (10/11) bzw. drei 4‐Isopropylidenbicyclo [3.2.0]‐2‐hepten‐6‐one (12/13), wobei das Stereoisomerenverhältnis 10:11 bzw. 12:13 von der Grösse der Ketensubstituenten beeinflusst wurde. Die Vinylketen‐Cycloaddukte 10/11 und 12/13 enthalten ein Cope‐System, das entweder in einer syn‐(10 und 12) oder in einer anti‐Konfiguration (11 und 13) vorliegt. Beim Erwärmen auf 140–190° ergaben 10/11 bzw, 12/13 durch Cope‐Umlagerung die entsprechend substituierten Bicyclo[4.2.1]‐3,7‐nonadien‐2‐one (14) bzw. 9‐Isopropylidenbicyclo[4.2.1]‐3,7‐nonadien‐2‐one (15). Mittels der beschriebenen Reaktionen werden die Ringsysteme von 14 und 15 in einer zweistufigen Synthese leicht zugänglich.
Malzoxazin, eine tricyclische Verbindung aus Gerstenmalz
Authors: Tressl Roland , Helak Bernd , Rewicki Dieter
Published: December 2004

Maltoxazine, a Tricyclic Compound from Malt

A new tricyclic compound, named maltoxazine, has been isolated from malt as well as from the reaction products formed in a model reaction of maltose with proline. The structure of maltoxazine (1) has been established by 1H‐ and 13C‐NMR. spectroscopy. The formation of 1 in several model reactions is strongly correlated with the formation of maltol and 5‐hydroxy‐5,6‐dihydromaltol.
(Perhalogenmethylthio)heterocyclen. XII. Herstellung von Perfluoroalkylsulfonylharnstoff‐Derivaten sowie CCl3−nFnX‐substituierten Heterocyclen und deren biologische Wirkung
Authors: Gerstenberger Michael R. C. , Haas Alois , Pauling Horst
Published: December 2004

(Perhalomethylthio)heterocycles XII. Preparation of Perfluoroalkylsulfonylurea Derivatives as well as CCl3−nFnX‐Substituted Heterocycles and Their Biological Activity

XI, Mitt., s.[1]

In the presence of CF3SO3H (chlorodifluoromethylthio)thiophene 1 reacts with CClF2SCl to give the 2,5‐disubstituted thiophene 2a which on oxidation with 30% H2O2‐solution yields the corresponding sulfonyl compound 2b · R1SO2NCO adds amines to give R1SO2NHC(O)NHR 3a–g. Some biological properties of these compounds were investigated.
Selektive Reaktionen an Cytochalasin D
Authors: Chappuis Georges , Tamm Christoph
Published: December 2004

In connection with the total synthesis of cytochalasans the cleavage of the macrocyclic system of cytochalasin D (3) was studied in order to gain useful relay compounds. Selective scission of the double bond in 19‐position was achieved by controlled ozonolysis leading to compound 7 (Scheme 1). Treatment of 3 with OsO4 and subsequent acetylation gave the tetraacetoxy‐ and diacetoxy derivatives 8 and 9, respectively. Sharpless epoxidation of 3 yielded the mono‐, di‐ and the two epimeric triepoxides 10, 11, 12, and 13, respectively.

Further studies concerned the isomerization of the 6(12)‐double bond to 6(7)‐double bond by an allylic rearrangement. Treatment of 3 with mesylchloride and triethylamine led to 12‐hydroxy‐, 12‐mesyloxy‐ and 12‐chlorozygosporin (14, 16, and 17, resp.) (see Scheme 2). Epoxidation of 14 gave a mixture of the two epimeric 6,7‐epoxides 21 and 23. Zn‐reduction of 18 (the corresponding bromide of 17) led to zygosporin G (20).

In order to convert a carbocyclic cytochalasan into a macrocyclic derivative, 3 was converted to 32 (Scheme 2). Treatment of 32 with H2O2 in acetic acid/chloroform or with phenylselenylperacid/H2O2 yielded the enollactone 33.

Finally, 17,18‐secocytochalasin D derivatives were prepared for the synthesis of unnatural analogs of macrolidic cytochalasans. The diol 26 was converted into the ketoaldehydes 38 and 40 and to the corresponding keto‐acids 43 and 44 (Scheme 3), which were reduced to the ω‐hydroxycarboxylic acids 45–48. Treatment of 47 with 2,2/‐dipyridyldisulfide/triphenylphosphine/xylene gave probably the lactone 50.
Lipophilic Diamides as Ionophores for Alkali and Alkaline Earth Metal Cations
Authors: Erne Daniel , Ammann Daniel , Zhukov Alex F. , Behm Felix , Pretsch Ernö , Simon Wilthelm
Published: December 2004

A series of lipophilic N, N, N′,N′‐tetrasubstituted diamides were prepared and their selectivity in solvent polymeric membranes was studied, cis‐N, N, N′, N′‐Tetraisobutylcyclohexane‐1,2‐dicarboxamide induces a selectivity in membranes for Li+over alkaline earth metal cations and other alkali metal cations by a factor of about 1000 and 100 respectively. The ionophore N, N′‐diheptyl‐N,N′‐dimethylethylmalonamide is an attractive candidate for the use in microelectrodes for the determination of intracellular Mg2+‐activities.
Zur Synthese sulfonierter Derivate von 4‐Fluoranilin
Authors: Courtin Alfred
Published: December 2004

Syntheses of Sulfonated Derivatives of 4‐Fluoroaniline

Synthesis of 2‐amino‐5‐fluorobenzenesulfonic acid (2) was achieved by baking the hydrogen sulfate of 4‐fluoroaniline (1). Sulfonation of p‐fluoroacetanilide (4) with oleum followed by hydrolysis gave 5‐amino‐2‐fluorobenzenesulfonic acid (3). The same reaction with 1 yielded 3 in an impure state. The structures of 2 and 3 were confirmed by converting the diazonium chlorides derived from 5‐fluoro‐2‐nitroaniline (5) and from 2‐fluofo‐5‐nitroaniline (8) to 5‐fluoro‐2‐nitrobenzene‐sulfonyl chloride (6) and 2‐fluoro‐5‐nitrobenzenesulfonyl chloride (9), respectively, followed by hydrolysis of 6 to 5‐fluoro‐2‐nitrobenzenesulfonic acid (7), and of 9 to 2‐fluoro‐5‐nitrobenzenesulfonic acid (10), and by final reduction. Compound 10 was also obtained by sulfonation of 1‐fluoro‐4‐nitrobenzene (11) with oleum.
Photochemical Synthesis of 9‐Methyl‐tetracyclo[5.3.04,9.08,10]‐decane‐2,6‐dione
Authors: Margaretha Paul , Grohmann Klaus
Published: December 2004

Irradiation (λ > 340 nm) cis‐8a‐methyl‐1,2,4a,7,8,8a‐hexahydronaphthalene‐2.7‐dione (1) in benzene affords the title compound 2 via an intramolecular [2 + 2]‐cycloaddition.
The Photoelectron Spectrum of [18]Annulene
Authors: Baumann Harold , Bünzli Jean‐Claude , Oth Jean Françcois Michael
Published: December 2004

The PE. spectrum of [18]annulene has been measured and correlated with MO‐calculations. The experimental ionization energies can only be explained by computing the electronic states of the cation, that is by taking into account the electron correlation and reorganization in the ionic states. The results allow a discussion of the structure of the neutral molecule; they are consistent with a D6hpoint group of symmetry.
Photochemical Reactions. 126th Communication. Photochemistry of an α, β: δ, ε‐unsaturated ketone: 4‐(2′, 7′, 7′‐Trimethylbicyclo [3.2.0]hept‐2′‐en‐1′‐yl)‐3‐buten‐2‐one
Authors: Ishii Keitaro , Lyle Terry A. , Schweizer W. Bernd , Frei Bruno
Published: December 2004

On 1n,π*‐excitation, the title compound 2 undergoes a photoinduced intramolecular [4 + 2]‐cycloaddition affording the tetracyclic enol ether 3 as the only product in 79% yield. The assigned structure of 3 was confirmed by its conversion to the p‐nitrobenzoate 6 whose structure was determined by X‐ray analysis.
Das Pyrrocorphin‐Ligandsystem: Synthese des 2,2,7,7,12,12,17‐Heptamethyl‐2,3,7,8,12,13‐hexahydroporphyrins. Kurzmitteilung
Authors: Sehwesinger Reinhard , Waditschatka Rudolf , Rigby James , Nordmann René , Schweizer Wolfhard B. , Zass Engelbert , Eschenmoser Albert
Published: December 2004

The Pyrrocorphin Ligand System: Synthesis of 2,2,7,7,12,12,17‐Heptamethyl‐2,3,7,8,12,13‐hexahydroporphyrin

Reaction Schemes 4 and 6 summarize the synthesis of the title compound, a representative of a recently described novel type of hexahydroporphinoid ligand system (‘pyrrocorphin’). Pyrrocorphins incorporate structural elements of both corrins and porphyrins and are chemically closely related to the tautomeric non‐pyrrolic corphins (Scheme 1).

The synthesis exemplifies a methodology for constructing pyrrolic hydro‐porphinoids with the methods of corrin instead of porphyrin synthesis. An X‐ray analysis of 2‐(cyanomethyl)‐2‐methyl‐3‐oxobutanamide has been carried out.
Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6‐Oxo‐isophoron. V. Synthese von Astacin
Authors: Widmer Erich , Lukáč Teodor , Zell Reinhard , Bernhard Kurt
Published: December 2004

Technical Procedure for the synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophorone

Teil 4 dieser Reihe: [1].

. V. Synthesis of Astacene

Starting from optically inactive astaxanthin intermediates, the highly oxygenated carotenoid astacene was synthesized in seven steps (55% overall yield from 6‐oxo‐isophorone). Key features of the new approach are base‐ and acid‐catalyzed rearrangements of acetylenic intermediates such as those described in Schemes 2, 7 and 8.
Unexpected Configurational and Conformational Preference in Bicyclo [3.2.0]heptane Systems
Authors: Rey Max , Roberts Stanley M. , Dreiding André S. , Roussel Albert , Vanlierde Huguette , Toppet Suzanne , Ghosez Léon
Published: December 2004

Einige 7endo‐monosubstituierte Bicyclo[3.2.0]hept‐2‐en‐6‐one and Bicyclo‐[3.2.0]heptan‐6‐one zeigen eine unerwartete thermodynamische Stabilität gegenüber den entsprechenden 7exo‐Isomeren. Die basenkatalysierte Epimerisierung (NaOH oder N(CH2CH3)3) verschiedener 7‐monosubstituierter Bicyclo[3.2.0]‐hept‐2‐en‐6‐one (1‐7) und Bicyclo[3.2.0]heptan‐6‐one (8–10) führt je nach Substituent (R) zu folgenden endo/exo‐Gleichgewichtsgemischen: (a) Bicyclo[3.2.0]‐hept‐2‐en‐6‐one: R = F: 89/11, R = C1: 87/13, R = CH3: 76/24, R = CH2CH3: 65/35, R = CH (CH3)2: 57/43, R= C (CH3)3: 10/90, R= C6H5: 66/34; (b) Bicyclo[3.2.0]‐heptan‐6‐one: R = C1: 85/15, R = CH3: 45/55, R= C (CH3)3: 0,4/99,6. In jedem Fall wurde das gleiche Epimerengemisch erhalten, ausgehend sowohl vom endo‐ wie auch vom exo‐Isomeren.

Die bemerkenswerte endo‐Stabilität wird einer Bevorzugung der Konformation 11 des Cyclobutanonringes zugeschrieben, verursacht durch geringere Pitzer‐Spannung. So kann ein endo‐Substituent an C(7) eine pseudoäquatoriale Lage am Cyclobutanonring einnehmen. Bei sehr sperrigen Substituenten mit zunehmender Raumerfüllung nimmt eine 1,2‐abstossende Wechselwirkung langsam überhand, bis im Falle des t‐Butylsubstituenten die exo‐Konfiguration die stabilere wird.

Die Dehalogenierung von 7‐Halo‐substituierten Bicyclo [3.2.0]hept‐2‐en‐6‐onen (15 bis 21) mit Zink und Eisessig und mit Tributylzinnhydrid führte zu den folgenden endo/exo‐Epimerengemischen der entsprechenden 7‐monosubstituierten Bicyclo [3.2.0]hept‐2‐en‐6‐one (2 bis 7): R = C1: 92/8, R = CH3: 93/7, R = CH2CH3: 93/7, R = CH(CH3)2: 92/8, R = C(CH3)3: 93/7, R = C6H5: 93/7. In allen Fällen, also unabhängig vom Substituenten R, war das endo‐isomere stark bevorzugt. Es muss sich also um eine kinetische Kontrolle im isomerenbestimmenden Schritt handeln: Die Reduktion verläft über das Enolat, bzw. über eine Radikalspezies mit trigonal‐planarer Anordnung am C(7), so dass die (irreversible) Wasserstoff‐Anlagerung von der weniger behinderten Site, der exo‐Seite her erfolgt.
Sterisch gehinderte Pyrrolidine. Umsetzung von 2,5,5‐Trimethyl‐1‐pyrrolin‐1‐oxid mit α‐Chloracrylnitril
Authors: Schneider Hermann
Published: December 2004

Reaction of the nitrone 1 with α‐chloroacrylonitrile (4) as ketene equivalent yields the 5‐isoxazolidinone 2a and the α‐chloroimine 5. The mechanism of the reaction is discussed. The compound 2a is useful for the synthesis of hindered pyrrolidines 3.
Die spontane Spaltung von 3,3‐Diäthyl‐5‐methylpiperidin‐2,4‐dion(Methyprylon) in die optischen Isomeren. Eine Rötgenstrukturanalyse eines isodimorphen Systems von Mischkristallen
Authors: Oberhänsli Willi E.
Published: December 2004

The Spontaneous Resolution of the 3,3‐Diethyl‐5‐methylpiperidine‐2,4‐dione (Methyprylon) into its Optical Isomers. An X‐Ray Structure Analysis of an Isodimoophous System of Mixed Crystals

Repeated recrystallizations from acetone of a racemic mixture of the title compound successively result in a spontaneous resolution into optical isomers [1]. In this process batches of mixed crystals of increased optical purity are formed [2]. This phenomena was investigated on a molecular basis using X‐ray diffraction methods. The mixed crystals belong to the space group P212121 and their diffraction patterns give no indication of major disorders. There is a linear relationship between the changes in unit cell parameters a and b and the optical rotation of the sample. The structures of the mixed crystals from four fractions belonging to two different crystalline modifications have been determined. The molecular shape is such that most of the atomic positions of the two enantiomers superimpose almost perfectly. Occupation factors determined for the asymmetric C‐ sites agree well with the optical activity of the crystals fraction.