bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese und Struktur porphinoider Nickel‐Komplexe mit axial orientierten Seitenketten
Authors: Mez Hans Christian , Löliger Jürg , Vogel Ulrich , Meier Kurt , Scheffold Rolf
Published: December 2004

Synthesis and Structure of Porphine‐type Nickel Complexes Containing Axially Oriented Sidechains

The structure of (±)‐[1, 11‐dimethoxy‐10 H‐HDP (2‐)]nickel (3), the product of the thermodynamically controlled addition of methanol to [6 H‐HDP]nickel‐bis‐(tetrafluoroborate) (1), was determined by X‐ray analysis. The two methoxy groups in 3 are cis‐oriented. The syntheses and spectroscopic properties of [1, 11‐diethoxy‐10 H‐HDP (2‐)]nickel (5), [1, 11‐dineopentyloxy‐10 H‐HDP (2‐)]nickel (6) as well as the bridged complexes [1, 11‐pentamethylenedioxy‐10 H‐HDP (2‐)]nickel (4) and [1, 11‐(E)‐2,3‐(dimethyl‐2‐butenylenedioxy)‐10 H‐HDP (2‐)]nickel (7) are described. Reaction of 1 with bromide ions or 4‐methylpyridine leads to the formation of the corresponding hexacoordinated, paramagnetic complexes dibromo [6 H‐HDP]‐nickel (II) (8) and bis (4‐methylpyridine)[6 H‐HDP]nickel‐bis (tetrafluoroborate) (9).
Anwendung der α‐Alkinon‐Cyclisierung: Synthese von rac‐Modhephen
Authors: Karpf Martin , Dreiding André S.
Published: December 2004

Application of the α‐Alkynone Cyclization: Synthesis of rac‐Modhephene

rac‐Modhephene 1, the first sesquiterpene with a propellane C‐skeleton and its epimer rac‐epi‐modhephene 27, were synthesized starting from bicyclo[3.3.0]oct‐1(5)‐en‐2‐one (2). The key step in the construction of the [3.3.3]‐propellane system is an application of the α‐alkynone cyclization, namely 3 → 4 and 11 → 14. The preferred formation of the propellanes 4 and 14 in this step shows that the insertion of the postulated alkylidene carbene intermediate into tertiary C,H‐bonds outweighs the one into the secondary ring‐C,H‐bonds leading to 12/13 and 15/16, respectively. The two starting materials for the α‐alkynone cyclization, 3 and 11, were prepared from 2 by the reactions shown in Scheme 3. The further elaboration and separation of the cyclization products 4 and 14 to rac‐modhephene 1 and its epimer 27 are outlined in Scheme 5.
Lithiierung in α‐Stellung zum N‐Atom von Triphenylacetamiden aus cyclischen sekundären Aminen. Umlagerung metallierter Triphenylacetamide unter 1,3‐Verschiebung der Carbamoylgruppe
Authors: Wykypiel Werner , Lohmann Jean‐Jaques , Seebach Dieter
Published: December 2004

Lithiation in α‐Position to the N‐Atom of Triphenylacetamides from Cyclic Secondary Amines. Rearrangements of Metalated Triphenylacetamides by 1,3‐Shift of Carbamoyl Groups

The reagents 2 ‐ generally available by lithiation of the triphenylacetamides 1 ‐ react with non‐enolizable carbonyl compounds and benzyl halide (s. Tables 1 and 2, and products 3). The limits of thermal stability of metalated triphenylacetamides above 0° are caused by a 1,3‐shift of the carbamoyl group into the o‐position of one of the benzene rings (s. 2b → 4 and 8a → 10). The barriers to rotation around the amide bonds of four triphenylacetamides are ca. 16 kcal/mol (s. 1b–e in Table 1).
Mechanisms of Diazo Coupling Reactions. Part XXX. N‐Diazo coupling of p‐chloroaniline in acetonitrile: Rate‐Limiting proton transfer
Authors: Penton John R. , Zollinger Heinrich
Published: December 2004

The N‐diazo coupling of p‐chloroaniline with p‐chlorobenzenediazonium tetrafluoroborate in acetonitrile at 30° shows non‐linear base catalysis by water. The results are interpreted in terms of the SE2 mechanism with rate‐limiting proton loss at low base concentration; it is postulated, moreover that the reaction proceeds via transition states in which varying degrees of H‐bonding from the amine and the intermediate ω‐complex to different water species influence the initial step and the base catalysis.
Über eine Ringerweiterungsreaktion an einem Barbitursäure‐Derivat. 10. Mitteilung über Umamidierungsreaktionen
Authors: Jenny Christjohannes , Hesse Manfred
Published: December 2004

A Ring Enlargement Reaction with a Barbiturate

The (6‐membered) barbituric acid derivative 3 was synthesized and treated with KF/DMF/18‐crown‐6 to form the ring‐enlarged 14‐membered compound 8 in good yield.
Notiz zur Synthese von Alkyl‐, Cycloalkyl‐ und Aryl‐3‐aminophenylsulfonen
Authors: Courtin Alfred
Published: December 2004

Syntheses of Some Alkyl, Cycloalkyl and Aryl 3‐Aminophenyl Sulfones

Syntheses of alkyl (1a–1i, 1m), cycloalkyl (1j, 1k) and aryl (1l) 3‐aminophenyl sulfones were achieved by ethanolic Béchamp‐reduction of the appropriate 3‐nitrophenyl sulfones (3a–3m). The alkyl (3a–3i) and cycloalkyl (3j, 3k) 3‐nitrophenyl sulfones were prepared via nitration of their respective sulfones (2a–2k). Methyl (3‐nitrophenyl) sulfone (3a) was also prepared by condensation of 3‐nitrobenzenesulfinic acid (4) with bromoacetic acid to 3‐nitrophenylsulfonyl‐acetic acid (5) followed by decarboxylation.
Structure and Dynamics of Intramolecular Hydrogen Bonds in Radicals: Substituent, steric and solvent effects
Authors: Loth Klaus , Graf Federico
Published: December 2004

The temperature and solvent dependence of the ESR. spectra of a number of semiquinone‐ and semidione‐type radicals have been investigated with the aim of obtaining structural and kinetic information about intramolecular hydrogen bonding. Systematic variation of the chemical structure of the radicals indicates that in many cases formation and/or exchange of intramolecular H‐bonds is disturbed or even precluded by steric hindrance or concomitant dynamic processes, such as internal rotation and/or intermolecular proton exchange.
Visible Light‐induced Oxygen Generation and Cyclic Water Cleavage Sensitized by Porphyrins
Authors: Borgarello Enrico , Kalyanasundaram Kuppuswamy , Okuno Yohmei , Grätzel Michael
Published: December 2004

Zinctetramethylpyridylporphyrin (ZnTMPyP4+) in acidic aqueous solution sensitizes efficiently oxygen generation by visible light in the presence of acceptors such as Fe3+ ‐ and Ag+‐ions and colloidal RuO2/TiO2 redox catalyst. Hydrogen and oxygen are cogenerated under visible light illumination of ZnTMPyP4+ solutions when a bifunctional catalyst (Pt and RuO2 codeposited onto TiO2) is employed.
19‐O‐Acetylchaetoglobosin B and 19‐O‐Acetylchaetoglobosin D, Two New Metabolites of Chaetomium globosum
Authors: Probst Alessandro , Tamm Christoph
Published: December 2004

Two new metabolites have been isolated from cultures of Chaetomium globosum. The structures of 19‐O‐acetylchaetoglobosin B (4) and 19‐O‐acetylchaetoglobosin D (5) are assigned. The 13C‐NMR. spectra of chaetoglobosin A (1), 19‐O‐acetylchaetoglobosin A (2), chaetoglobosin C (3), 19‐O‐acetylchaetoglobosin B (4), 19‐O‐acetylchaetoglobosin D (5) and of cytochalasin G (6), a (3‐indolyl)‐[11]cytochalasan isolated from Pseudeurotium zonatum, have been interpreted.
Biosynthesis of the Cytochalasans. Biosynthetic studies on chaetoglobosin A and 19‐O‐acetylchaetoglobosin A
Authors: Probst Alessandro , Tamm Christoph
Published: December 2004

Incorporation of [1‐13C]‐, [2‐13C]‐ and [1,2‐13C2]‐acetate, [1‐13C]‐propionate, [13C‐CH3]‐L‐methionine and [3‐14C]‐DL‐tryptophan into chaetoglobosin A (1) and 19‐O‐acetylchaetoglobosin A (2) by Chaetomium globosum demonstrated that the building blocks of 1 and 2 are 9 and 10 units of acetate/malonate respectively, 3 units of methionine and 1 unit of tryptophan. Propionate is incorporated indirectly after several biological transformations. Using [2‐13C, 2‐2H3]‐acetate as precursor, the starter unit of the polyketide‐chain was identified. Experiments which [13C, 2H3‐CH3‐L‐methionine demonstrated that the three C‐methylations occur with retention of all three H‐atoms of the methyl group. Incorporation experiments with various 14C‐ and 3H‐labelled tryphtophan samples and with [2‐2H]‐ and [2‐15N]‐L‐tryptophan showed that the amino acid is incorporated intact with retention of both the α‐H‐ and the α‐N‐atom. On the basis of these results a more detailed general scheme of the cytochalasan biogenesis is proposed.
Nucleosides and Nucleotides. Part 17. A simple preparation of protected deoxynucleoside‐3'‐phosphates
Authors: Bernardini Silvio , Waldmeier Felix , Tamm Christoph
Published: December 2004

A simple method for the preparation of fully protected 2′‐deoxynucleoside‐3′‐phosphates is described. The main step, phosphorylation of partially protected deoxynucleosides, is performed with the monofunctional reagent p‐chlorophenyl (2‐cyanoethyl) phosphochloridate3) (2) in dioxane. This reagent is quickly prepared from readily accessible p‐chlorophenyl phosphodichloridate by reaction with 3‐hydroxypropionitrile and triethylamine in dioxane or ether. The crude reagent is used directly for phosphorylation. After chromatography, protected deoxynucleoside‐3′‐phosphates were isolated in yields of 80–87%. The method described here, which has been optimized in detail, represents a simple alternative to published methods.
Self‐Sensitized Photo‐Oxygenation of 1‐Benzyl‐3, 4‐dihydroisoquinolines
Authors: Martin Ned H. , Jefford Charles W.
Published: December 2004

The air oxidation of 1‐benzyl‐3, 4‐dihydroisoquinolines is shown to be a self‐sensitized photo‐oxidation proceeding via singlet oxygen.
Partialsynthese der Grandidone A, 7‐Epi‐A, B, 7‐Epi‐B, C, D und 7‐Epi‐D aus 14‐Hydroxytaxodion
Authors: Rüedi Peter , Uchida Masaaki , Eugster Conrad Hans
Published: December 2004

Partial Synthesis of Grandidones A, 7‐Epi‐A, B, 7‐Epi‐B, C, D and 7‐Epi‐D, from 14‐Hydroxytaxodione

Oxydative addition of coleon U (6) to 14‐hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7‐epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7‐epigrandidone B (2b) (ca. 3:1). Dimerization of 14‐hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7‐epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7‐epigrandidone D (4b) and interconversions of 4a and 4b were achieved.

Oxydative addition of coleon U (6) to 14‐hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7‐epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7‐epigrandidone B (2b) (ca. 3:1). Dimerization of 14‐hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7‐epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7‐epigrandidone D (4b) and interconversions of 4a and 4b were achieved.

Oxydative addition of coleon U (6) to 14‐hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7‐epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7‐epigrandidone B (2b) (ca. 3:1). Dimerization of 14‐hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7‐epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7‐epigrandidone D (4b) and interconversions of 4a and 4b were achieved.

Oxydative addition of coleon U (6) to 14‐hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7‐epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7‐epigrandidone B (2b) (ca. 3:1). Dimerization of 14‐hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7‐epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7‐epigrandidone D (4b) and interconversions of 4a and 4b were achieved.
Über einen neuartigen synthetischen Zugang zu β,γ‐ungesättigten α‐Aminocarbonsäuren
Authors: Heinzer Franz , Belluš Daniel
Published: December 2004

A New Synthetic Route to β,α‐Unsaturated α‐Amino Acids

A versatile new synthetic pathway for the preparation of βγ‐unsaturated α‐amino acids (1) is presented. Cu(I)‐catalyzed addition of ethyl isocyanoacetate (2) to α‐chloro carbonyl compounds (3) gives 5‐chloroalkyl‐2‐oxazolin‐4‐carboxylates (4) in high yields. A reductive elimination on4by means of zinc yields theN‐formyl derivatives of βγ‐unsaturated α‐amino carboxylates (5), which on acid hydrolysis lead to the free amino acids1. The five different βγ‐dehydro‐α‐amono acids1b‐1fhave been prepared by this method.
Synthèse de nouveaux types de dérivés C‐glycosyliques à partir de sucres acétyléniques ou de leurs équivalents synthétiques partiels
Authors: Tronchet Jean M. J. , Bonenfant Alain P.
Published: December 2004

Synthesis of Novel Types of C‐Glycosyl‐derivatives from Acetylenic Sugars or Partial Synthetic Equivalents thereof

The concept of synthetic equivalent is not unequivocal and, for example, α‐fluoroenamines may behave in some cases as synthetic equivalents of ynamines and, in other situations, quite differently. Some uses of these α‐fluoroenamines, ‘partial synthetic equivalents’ of ynamines, for the synthesis of C‐glycosyl derivatives of coumarins, chromones, quinolines, quinolones, thietenes and isoxazoles are described.

We also report the preparation of a series of mono‐ and diglycosylthiophenes by reacting HS− with mono‐ and diglycosylbutadiynes. Acetylenic sugar derivatives have also been used for the synthesis of a diglycosylazaphosphorine and a spirooxolenone.
The Occurrence of Some Novel Diesters in Roman Camomile Oil
Authors: Thomas Alan F.
Published: December 2004

Three diols, 2‐methylidene‐1,3‐propanediol, 2‐methyl‐1,3‐propanediol and 1,3‐butanediol, esterified on one hydroxyl group with isobutyric acid and on the other with angelic acid1), have been isolated from Anthemis nobilis oil (Roman camomile) and synthesized. The presence of homologous esters is very probable.
Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus Oxo‐isophoron. I. Modifizierung der Kienzle‐Mayer‐Synthese von (3S 3′S)‐Astaxanthin
Authors: Widmer Erich , Zell Reinhard , Lukáč Teodor , Casadei Marco , Schönholzer Peter , Broger Emil A.
Published: December 2004

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophorone. I. Modification of the Kienzle‐Mayer‐Synthesis of (3S, 3′S)‐Astaxanthin

An efficient synthesis of (3S, 3′S)‐astaxanthin (1a) in high yield and optical purity starting from (4R, 6R)‐4‐hydroxy‐2,2,6‐trimethylcyclohexanone (4) is reported. The absolute configuration of 1a, previously derived from ORD. data, has been confirmed by X‐ray analysis of 5, a derivative of 6‐oxo‐isophorone (2). The key features of the improved synthesis are the two‐step conversion of 4 to the key intermediate (4S)‐2,6,6‐trimethyl‐4‐hydroxy‐2‐cyclohexen‐1‐one (14), a new method for the partial reduction of the sterically hindered triple bond of (S)‐6‐hydroxy‐3‐(5‐hydroxy‐3‐methyl‐3‐penten‐1‐ynyl)‐2,4,4‐trimethyl‐2‐cyclohexen‐1‐one (32), and Wittig olefination of the dialdehyde 1,6‐dimethyl‐1,3,5‐octatrienedial (38) using phosphonium salt 37 with a free hydroxyl group.
13C‐NMR. Spectral Differences between Corresponding Methyl Esters, Phenyl Esters and 2‐Substituted Chromones
Authors: Séquin Urs
Published: December 2004

The 13C‐NMR. spectra of 2‐substituted chromones (3) are compared with the data of the analogous methyl and phenyl esters (1 and 2). The chemical shift differences found are most prominent for the C‐atoms in β‐position to the ester carbonyl and chromone C(2), respectively. These shift differences are discussed in terms of conformational differences between the esters 1 and 2 and the analogous chromones 3.
Kreuzkonjugierte Cyanine und Merocyanine aus Salzen 1‐substituierter 2,3‐Dimethylchinoxaline. 1. Mitteilung. Über die Isolierung der Farbbasen nach spontaner Umwandlung und nach Oxydation der Reaktanten mit Kupfer(II)acetat oder Silberoxid
Authors: Schelz Dieter
Published: December 2004

Cross‐conjugated Cyanines and Merocyanines, Obtained from Salts of 1‐Substituted 2,3‐Dimethylquinoxalines. 1. Communication

Vorläufige Mitteilung siehe [1].

.
On the Isolation of the Dye Bases Formed upon a Spontaneous Reaction on upon Oxidation of the Reactants with Copper(II) Acetate or Silver Oxide

Quaternary salts of 2,3‐dimethylquinoxalines 1 ‐ in some cases in the presence of the methylidene bases 2 ‐ yield, on dissolving in dimethyl sulfoxide or dimethyl‐formamide, the dye bases 3 in a spontaneous reaction. Higher yields of 3 are obtained by oxidation of 1, 2 or 1/2 with copper (II) acetate or silver oxide. VIS. and 1H‐NMR. spectra of the dyes are given. Their structural relationship to Hünig's [2] [8] two‐step‐redox systems is discussed.
Die Synthese von 6‐substituierten 2‐Norbornanolen. Norbornane, 7. Mitteilung
Authors: Grob Cyril A. , Günther Bettina , Waldner Adrian
Published: December 2004

The Synthesis of 6‐substituted 2‐Norbornanols

The preparation of several 6‐exo‐ and 6‐endo‐substituted 2‐exo‐ and 2‐endó‐norbornanols and their p‐toluenesulfonates is described.
Secondary Deuterium Isotope Effect in an Electrophilic Aromatic Substitution ‐ Protodesilylation of Trimethylphenylsilane
Authors: Szele Ivanka
Published: December 2004

Reaction rates for the protodesilylation of trimethylphenylsilane and of [2,4,6‐2H3]‐trimethylphenylsilane by HCIO4, were measured in aqueous methanol (2:5, v/v) and the secondary deuterium isotope effect for the reaction was found to be kH/kD3 = 0.79. The magnitude of the observed isotope effect supports a mechanism in which the rate‐determining step is the proton transfer from the hydronium ion to the silane to form a σ‐intermediate.
Synthesen von (1R)‐cis‐3‐(2′,2′‐Dihalovinyl)‐2, 2‐dimethylcyclopropan‐carbonsäuren via Favorskii‐Umlagerung von optisch aktiven Cyclobutanonen
Authors: Greuter Hans , Dingwall John , Martin Pierre , Belluš Daniel
Published: December 2004

Syntheses of (1R)‐cis‐3‐(2′,2′‐Dihalovinyl)‐2,2‐dimethylcyclopropane Carboxylic Acids via Favorskii‐rearrangement of Optically Active Cyclobutanones

The cis‐cyclobutanones 7 are resolved by means of optically active amine salts of their sodium hydrogen sulfite adducts. The desired (1R)‐cis‐carboxylic acids 9 are obtained from the (+)‐cis‐cyclobutanones 7 via Favorskii‐rearrangement and HX‐elimination. The recycling of undesired (−)‐cis‐cyclobutanones 7 is carried out in good yield by their racemization, thus rendering the total synthesis 1+2→9 chirally economic.
Photodimerization of Solid Pleiadiene; Isomerization and Cycloreversion of the Dimer
Authors: Hazell Alan C. , Pagni Richard M. , Persy Gabriele , Rommel Erika , Wirz Jakob
Published: December 2004

Irradiation (λ>400 nm) of solid pleiadiene (1) yields a single, head‐to‐head [π4s+π4s]‐photodimer (2) the structure of which was determined by X‐ray analysis. The formation of 2 is entirely suppressed at 77 K, since properly oriented pairs of molecules arise only from thermal disorder in crystals of 1. Upon pyrolysis (80°), the strained photodimer 2 rearranges to the [π2s + π4s] dimer 3 by a ‘forbidden’ suprafacial [1,3]‐C‐atom migration. Both 2 and 3 are reconverted to 1 by UV. irradiation in solution, but the latter, ‘forbidden’ photoreaction is suppressed at 77 K. Discrepancies of the experimental observations with the predictive schemes of Kaupp or Michl are discussed.
Inductive and Polarizability Effects of an Exocyclic Diene‐Iron Tricarbonyl Group. The acetolyses of exo‐ and endo‐irontricarbonyl complexes of 5,6‐dimethylidene‐2‐exo‐norbornyl and 2,3‐dimethylidene‐7‐anti‐norbornyl parabromobenzenesulfonates
Authors: Barras Charles , Bell Larry G. , Roulet Raymond , Vogel Pierre
Published: December 2004

The exo‐ and endo‐irontricarbonyl complexes of 5,6‐dimethylidene‐2‐exo‐norbornyl alcohols 10x, 10n, p‐bromobenzenesulfonates 11x, 11n, acetate 12x and of the 2,3‐dimethylidene‐7‐anti‐norbornyl alcohols 17x, 17n, p‐bromobenzenesulfonates 19x, 19n and acetates 20x, 20n have been prepared. The SN1 buffered acetolyses of 11x, 19x and 19n gave 12x, 20x and 20n, respectively (retention of configuration). The first‐order rate constants of the acetolyses have been evaluated and compared with those of the acetolyses of the uncomplexed 5,6‐dimethylidene‐2‐exo‐norbornyl (14) and 2,3‐dimethylidene‐7‐anti‐norbornyl p‐bromobenzenesulfonates (18). A rate retardation effect of ca. 1.5 · 105 was measured for 11x → 12x (65°) compared with the acetolysis of 14. The retardation effect is larger (> 5 · 107) with 11n. Contrastingly, the acetolysis 19x → 20x was slightly accelerated with respect to that of the uncomplexed p‐bromobenzenesulfonate 18. An unsignificant rate‐retardation effect was measured for the acetolysis 19n → 20n. The results are interpreted in terms of competitive inductive destabilization and charge‐induced dipole stabilizing interaction by the exocyclic diene‐iron tricarbonyl fragment. PMO. arguments give a rationale for the difference in polarizability between the diene‐Fe(CO)3 group in 19 and that in the endo‐7‐norbornadienyl‐iron tricarbonyl system.
Stoffwechselprodukte von Mikroorganismen. 210. Mitteilung. Über die Avilurekanosen A and C and weitere Abbauprodukte Avilamycine A and C
Authors: Kupfer Ernst , Neupert‐Laves Katarina , Dobler Max , Keller‐Schierle Walter
Published: December 2004

The Avileurekanoses A and C and Further Degradation Products of the Avilamycins A and C

Alkaline hydrolysis of the orthosomycin antibiotics, avilamycins A ad C products similar t those earlier described for flambamycin. Among these avileurekanose c (15) became of particular importance because its acetate prisms suitable for an X‐ray structural determination. For the avilamycins A and C structural formulae 2 and 3, respectively, can now be drawn, in which only the configuration at C (16), one out of 32 asymmetric C‐atoms, is not yet determined.
Regioselectivity of the Diels‐Alder Additions of 2‐Substituted 5,6 Dimethylidenenorbornanes and‐bicyclo[2.2.2]octanes
Authors: Avenati Marco , Carrupt Pierre‐Alain , Quarroz Daniel , Vogel Pierre
Published: December 2004

The cycloadditions of methyl propynoate and methyl vinyl ketone to 5,6‐dimethylidene‐2‐norbornanone (6) are para′‐regioselective

“Para” (p) designs in this paper the 4, 9‐disubstituted tricclo[6.2.1.02, 7] undecane‐ and 4, 9‐disubsstituted tricycle[6.2.202,7] dodecane derivatives, “meta” (m) design the corresponding 4, 10‐disubstituted compounds.

. A smaller para ‐regioselectivity is observed for the addition of methyl propynoate to 5,6‐dimethylidene‐2bicyclo[2.2.2]octanone (10). No regioselectivity is observed with 5,6‐dimethylidene‐2exo‐norbornyl alcohol (3), acetate (5) and 5,6‐dimethylidene‐2exo‐bicyclo[2.2.2]octanol (9). PMO arguments based on the shape of the HOMO's and subHOMO's of the dienes allow to rationalize these observations. Unpredictable para′‐ or ‘meta’regioselectivities are found for the Diels,‐Alder additions of 5,6‐dimethylidene‐2endo‐norbornyl alcohol (2), acetate (4) and 5,6‐dimethylidene‐2endo‐bicyclo[2.2.2]octanol (8). The carbonyl group of β,γ unsaturated ketones such as 6 and 10 can act as an electron donating homoconjugated substituent. The n(CO) ↔ σ[C(1), C(2)] ↔ π[C(5), C(6)] hyperconjugative interaction can override the usual electron‐withdrawing effect of this function.
Synthesis, Conformation, and Interactions with Small Molecules of Bis (Cyclic Dipeptides)
Authors: Tomiyasu Hiroshi , Kinjura Shunsaku , Imanishi Yukio
Published: December 2004

Bis (cyclic dipeptides), cyclo and S, S′‐bis(cyclo(hemiCys‐Pro)), were synthesized. These bis (cyclic dipeptides) very efficiently formed complexes with Ba2+ and Na+ owing to intramolecular cooperation of two cyclicdipeptide moieties, the bis‐effect. Cyclo stacked sodium 8‐anilino‐1‐naphthalensulfonate in aqueous solution. These properties of complexation were controlled by the nature of the bridge connecting two cyclic dipeptide moieties. The geometry of the complex between S, S′‐bis (cyclo (hemiCys‐Pro)) and metal ion was investigated with the help of circular dichroism, nuclear magnetic resonance, and Raman spectroscopy.
31P‐, 119Sn‐ and 195Pt‐NMR. Studies of Trichlorostannate Complexes of Pt(II) and Pd(II). 2J(119Sn, 117Sn)‐Values
Authors: Starzewski Karl H. A. Ostoja , Pregosin Paul S. , Rüegger Heinz
Published: December 2004

The synthesis and solution structures of new four‐ and five‐coordinate phosphine and arsine complexes of Pt and Pd containing the trichlorostannate ligand are described. Complexes containing two and three SnCl−3‐ligands have been identified from their 31P‐, 119Sn‐ and 195Pt‐NMR. spectra. The complexes trans‐[M (SnCl3)2L2] (M = Pt, L‐PEt3, PPr3, AsEt3; M = Pd, L = AsEt3) show unexpectedly large 2J(119Sn, 117Sn)‐values (34,674–37,164 Hz) with the trans‐orientation of these spins playing an important role. The heteronuclear coupling constant 2J(119Sn, 31P) in the five‐coordinate cationic complexes [Pt(SnCl3)(P(o‐AsPh2C6H4)3)]+ and [Pt(SnCl3)(As(o‐PPh2C6H4)3)]+ also shows a geometric dependence. New five‐coordinate anionic complexes of type [M (SnCl3)3L2]− (M = Pd, Pt; L = PEt3, AsEt3) may be prepared via addition of three mol‐equiv. of SnCl2 and one mol‐equiv. of (PPN)Cl to [MCl2L2] in acetone.
Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Struktur des porphinoiden Ligandsystems
Authors: Pfaltz Andreas , Jaun Bernhard , Fassler Alexander , Eschenmoser Albert , Jaenchen Rolf , Gilles Hans Harald , Diekert Gabriele , Thauer Rudolf K.
Published: December 2004

Factor F430 from Methanogenic Bacteria: Structure of the Porphninoid Ligand System

A structure is proposed for F430M, a non‐cristalline methanolysis product of isolates of the nickel‐containing, porphinoid factor F430 from Methanobacterium thermoautotrophicum.

Crucial to the structure determination are five incorporation experiments with M. thermoautotrophicum (strain Marburg) in which the specifically mono‐13C‐labeled biosynthetic precursors (2‐13C), (3‐13C), (4‐13C)‐, (5‐13C) ALA (ALA = δ‐amino‐levulinic acid) and L‐(methyl‐13C)methionine were incorporated into F430 with high efficiency. The 13C‐NMR,‐spectra of the specifically labeled F430M samples derived therefrom, together with the UV./VIS. spectral data of F430M, contain all the information necessary for the deduction of the constitution of the F430M chromophore, assuming the established pattern of porphinoid biosynthesis to be operative in F430 biosynthesis. 1H‐NMR. spectroscopy and, in particular, 1H‐NMR.‐NOE‐difference spectroscopy corroborates and completes the constitutional assignments and, furthermore, makes possible an almost complete derivation of the molecule's relative configuration. Schemes 3 and 4 summarize the results of 1H‐NMR. spectroscopy, presenting them within the context of the proposed structure for F430M. The assignment of absolute configuration implied in the formula is given preference because of F430M's very close structural and (assumed) biosynthetic relationship to sirohydrochlorin and vitamin B12 (with respect to ring C, the assignment is based on degradative evidence).

According to the proposed structure, the nickel complex F430M possesses an uroporphinoid (Type III) ligand skeleton with an additional carbocyclic ring and a chromophore system not previously encountered among natural porphinoids. It can be considered to be a (tetrahydro) derivative of the corphin system, combining structural elements of both porphyrins and corrins.
Effects of Remote Substitution on the Photo‐oxidation of Exocyclic s‐cis‐Butadienes Grafted onto Bicyclo [2.2.1]heptanes. Thermal and Rhodium Catalyzed Rearrangements of 3,6‐Dihydro‐1,2‐dioxines
Authors: Hagenbuch Jean‐Pierre , Birbaum Jean‐Luc , Métral Jean‐Luc , Vogel Pierre
Published: December 2004

The rates of photo‐oxidation of exocyclic S‐cis‐butadienes grafted onto bicyclo‐[2.2.1]heptanes and 7‐oxabicyclo[2.2.1]heptanes (1–6) are dependent upon remote modifications of the bicyclic skeletons. They correlate with the rates of Diels‐Alder additions of these dienes to strong dienophiles. The 2,3‐dimethylidenenorbornane (1), 5,6‐dimethylidene‐2‐norbornene (2) and 2,3‐dimethylidene‐7‐oxanorbornane (3) gave the corresponding endo‐peroxides (3,6‐dihydro‐1,2‐dioxines) 7–9 in good yield. The 2, 3, 5, 6‐tetramethylidene‐7‐oxanorbornane (4) gave the mono‐endo‐pe‐roxide 6, the latter did not react with a second equivalent of oxygen. Similarly, 5, 6‐dimethylidene‐7‐oxa‐2‐norbornene (5) was unreactive toward photo‐oxidation. Thermal isomerization of the endo‐peroxides 7 and 9 gave, the trans‐diepoxides 10 and 14, respectively, with high stereoselectivity. The endo‐peroxides 6, 7 and 9 were cleanly isomerized into the corresponding α, β‐unsaturated γ‐hydroxy aldehydes in the presence of catalytic amounts of Rh2(CO)4Cl2.
Electronic and Molecular Structure of Simple 3,3′‐Bicyclopropenyls. Photoelectron Spectroscopy and Model Calculations
Authors: Spanget‐Larsen Jens , De Korswagen Carla , Eckeri‐Maksie Mirjana , Gleiter Rolf
Published: December 2004

The electronic and molecular structure of 3,3′‐bicyclopropenyl (1) and its alkyl derivatives 3,3′‐dirnethyl‐3,3′‐bicyclopropenyl (2), dispiro [2.0.2.3]nona‐1,5‐diene (3), dispiro[2.0.2.4]deca‐1,5‐diene (4), dispiro [2.0.2.5]undeca‐1, 5‐diene (5), and dispiro [2.0.2.6]dodeca‐1, 5‐diene (6) are studied by means of photoelectron spectroscopy and model calculations. Through‐bond' effects in model compound 1 are analyzed in detail, illustrating a general difficulty with NDO models. Low‐energy photoelectron bands of 2–6 can be assigned to ejection of electrons from cyclo‐propenyl π‐ and Walsh‐orbitals. Strong ‘through‐bond’ coupling leads to splitting of the π‐bands in the range 1.0–1.5 eV, while the strongly conformation‐dependent splitting of the Walsh‐bands allows conclusions concerning the preferred torsional angles. The preference of a gauche‐conformation is predicted for 2 in the gas phase.
Chromatographische Trennung und Identifizierung diastereomerer Carotinoide mit grossem räumlichem Abstand der chiralen Zentren
Authors: Vecchi Max , Englert Gerhard , Mayer Hans
Published: December 2004

Chroma to graphic Separation and Identification of Diastereomeric Carotinoids with Distant Chiral Centers

The high‐performance liquid chromatographic separation of diastereomeric C40‐carotinoids is described possessing chiral centers which are separated by 18 C‐atoms (nonaene system). The method is applied to the separation of the two diastereomers of 6,6′‐dihydrorhodoxanthin 1a and 1b (ε,ε‐carotene‐3,3′‐dione) and the six diastereomers of tunaxanlhin (ε,ε‐carotene‐3,3′‐diol; 2a–2f). Conditions for the separation of lutein [(3R, 3′R, 6′R)‐β,ε‐carotene‐3.3′‐diol, 3a], 3′‐epi‐lutein [(3R,3′S,6′R)‐β, ε‐carotene‐3,3′‐diol, 3b] and its 13′‐cis‐ (3c) and 13‐cis‐stereo‐isomers(3d) are also reported. Identification of the different chromatographic fractions was possible by use of authentic synthetic samples or by 1H‐NMR. spectroscopy.
Herstellung und Solvolyse von 3‐substituierten p‐Toluolsulfonsäure‐(1‐adamantyl)estern
Authors: Bielmann Rolf , Grob Cyril A. , Schaub Bruno
Published: December 2004

The Preparation and Solvolysis of 3‐substituted 1‐Adamantyl Toluenesulfonates

Methods for the preparation of some hitherto unknown 3‐iubstitutetl 1‐adamantyl toluenesulfonates are evaluated. Their solvolysis products in dioxane/water 70:30 are reported.
17O‐NMR. of Enriched Acetic Acid, Glycine, Glutamic Acid and Aspartic Acid in Aqueous Solution. II. Relaxation Studies
Authors: Gerothanassis Ioannis P. , Hunston Roger , Laulenvein Jürgen
Published: December 2004

The 17O‐NMR. line widths of the enriched amino acids glycine, aspartic acid, glutamic acid and, for comparative reasons, acetic acid were measured in aqueous solution between pH 1 and 14. The 17O‐NMR. line‐width maxima of glycine at pH≈︁11 and acetic acid at pH≈︁5 are shown to arise from traces of paramagnetic metal ions. The increase in line width in case of glycine on going from the zwitterion 10 the cataion is attributed to an increase in the 17O‐quadrupole coupling constant. No evidence for an intermolecular or intramolecular association of glycine in the zwitterionic form was found. When the paramagnetic impurities were eliminated by addition of EDTA, both the longitudinal and transverse relaxation times remained unchanged on deprotonation of the amino group. The overlapping of the α, β‐ and α, γ‐carboxyl resonances of aspartic and glutamic acid, respectively, created difficulties for their line‐width analysis.
Stoffwechselprodukte von Mikroorganismen. 216. Mitteilung. Isolierung, Strukturaufklärung und Synthese von Ferrioxamin H
Authors: Adapa Srinivas , Hubtr Peter , Keller‐Schierlein Walter
Published: December 2004

Metabolites of Microorganisms. 216. Isolation, Structure and Synthesis of Ferrioxamine H

The structure of ferrioxamine H, a minor component of the sideramine complex of actinomycetes, was determined by spectroscopic investigations, degradation and synthesis. Ferrioxamine H is the Fe (III)‐complex of 11,22‐dihydroxy‐4, 12, 15, 23‐tetraoxo‐5,11,16,22‐tetraazatetracosanoic acid (2).
Diterpenoide Drüsenfarbstoffe aus Labiaten: 22 neue Coleone und Royleanone aus Plectranthus lanuginosus
Authors: Schmid Jean Martin , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Leaf‐gland Pigments from Labiatae: 22 Novel Diterpenoids (Coleons and Royleanones) from Plectranthus lanuginosus

We report the isolation and structure elucidation of 22 novel diterpenoids (named lanugones A, B, C, D, E, F, G, H, I, J, K, K′, L, M, N, O, P, Q, R, S and (155)‐coleon C (28) and (155)‐coleon D (29)) from the leaf‐glands of the above‐mentioned plant (see Table 1). Structurally they belong to the subgroups of royleanones and coleons with the following structural characteristics: 8‐hydroxy‐1‐methyl‐spi‐ro[2,5]oct‐5‐ene‐4,7‐diones, p‐quinomethanes, extended (vinylogous) quinones, di‐osphenols and diketones. Compounds 28 and 29 are (15S)‐epimers of the already known coleon C and coleon D (with (15 R)‐configuration), respectively. Furthermore, the already known 6,7‐didehydroroyleanone (1) has been isolated in small amount.

The present investigation has uncovered the broadest range of diverse chromo‐phoric systems and oxydation levels so far found amongst diterpenoids in a single plant species. Most important for an understanding of the metabolic fate of an iso‐propyl group is the full range found with the following metabolic stages: isopropyl‐→ hydroxyisopropyl → dihydrofuran and spirocyclopropane → allyl‐ and 2‐hydroxypropyl groups.
A Stereocontrolied Entry to Racemic Eremophilane and Valencane Sesquiterpenes via an Intramolecular Diels‐Alder Reaction
Authors: Näf Ferdinand , Decorzant René , Thommen Walter
Published: December 2004

A stereocontrolied route to racemic eremophilane and valencane sesquiterpenes is described via a common intermediate 15, accessible from an intramolecular Diels‐Alder reaction. 13C‐NMR.‐shift assignments of the bicyclic intermediates and products are presented.
Desoxy‐nitrozucker. 3. Mitteilung. Synthese von Ketosen durch Kettenverlängerung von 1‐Desoxy‐1‐nitro‐aldosen. Nucleophile Additionen und Solvolyse von Nitroaethern
Authors: Aebischer Bernard , Bieri Jost H. , Prewo Roland , Vasella Andrea
Published: December 2004

Synthesis of Ketoses by Chain Elongation of 1‐Deoxy‐1‐nitroaldoses. Nucleophilic Additions and Solvolysis of Nitro Ethers

A method for the preparation of chain elongated uloses based upon the base‐catalyzed addition of 1‐deoxy‐1‐nitroaldoses to aldehydes and Michael acceptors and subsequent solvolytic replacement of the nitro group by a hydroxy group is described. Thus, addition of 1, 3 and 9 to formaldehyde, followed by solvolysis gave the chain elongated ulose derivatives 2, 8 and 10 (63–76%), respectively. The configuration at the anomeric center of the addition products was deduced from 13C–NMR. spectra and mutarotation. In the case of 3, the primary addition products 4 and 6 were isolated and acetylated to 5 and 7. The nitro derivatives 4–7 do not follow Hudson's rule of isorotation. Addition of 1 to benzaldehyde (44%) and to nonanal (74%) preceded with a small degree of diastereoselectivity to give 15a/15b, and 11/12, respectively. The configuration of the secondary hydroxyl group of 12 was determined by correlation with methyl 2‐hydroxydecanoate (14). Addition of 1 to the galacroaldehyde 16 gave a single compound 17 (78%). The structure of this dodecosulose was determined by X‐ray crystallography. Solvolysis of the acetylation product 18 in formamide gave the hemiacetal 19 (69%). Michael addition of 1 to acrylonitrile, methyl vinyl ketone and cyclohexenone under solvolytic conditions gave the hemiacetals 27, 30 and 31a,b (49%, 71% and 76%, respectively). Under non‐solvolytic conditions (Bu4NF), 1 reacted with acrylonitrile, and crotononitrile to give the anomeric nitro ethers 23 and 24 (67%) and 25 and 26 (84%). respectively. Similarly. 3 added to acrylonitrile to give 28 and 29 (55%, 4:1). This reaction appears to proceed under kinetic control. Addition of 1 to ethyl propiolate and solvolysis yielded the unsaturated spirolactone 32 (50%) and the hemiacetal 33 (17%). Hydrogenation of 32 gave the saturated spirolactone 34 (100%) which was also obtained from 1 and methyl acrylate (63%). Addition of 1 to dimethylmaleate gave the unsaturated ester 35 (48%).
New Peptide Lactones of the Streptogramin Family (Group B). Structures of Virginiamycin S5 and Viridogrisein II
Authors: Oberbäumer Ilse , Grell Ernst , Raschdorf Fritz , Richter Wilhelm J.
Published: December 2004

Virginiamycin S5 and viridogrisein II were isolated by liquid chromatography from the crude antibiotics virginiamycin and viridogrisein, respectively. Their structures were elucidated by amino‐acid analysis and mass spectrometry.
Broad Nematic Phases with High Clearing Points
Authors: Osman Maged A.
Published: December 2004

Unbranched 4‐(4′‐alkylbenzoyloxy)‐, 4‐(4′‐methylanlinobenzoyloxy)‐ and 4‐(4′dime thylaminobenzoyloxy)benzylidene‐4″‐cyanoanmlines were synthesized. They show broad nematic phases with high nematic isotropic transitions. Lateral Clsubstituents decrease the clearing points of these liquid crystals by about 80°. The intermediate 4‐(4′‐alkylbenzoyloxy)benzaldehydes are monotropic nematic.
‘Non‐Koopmans’ States in Stilbene Cations and a Remarkable Example to the «SDT‐Equation»: Indeno [2,1‐a]indene
Authors: Haselbach Edwin , Klemm Urs , Gschwind Rudolf , Bally Thomas , Chassot Laurant , Nitsche Stephan
Published: December 2004

The radical cations of indeno [2, 1‐a]indene (1), stilbene (2) and 3, 5, 3', 5'‐tetramethylstilbene (3) were prepared by γ‐irradiation of the neutral precursors in an electron‐scavenging matrix at 77 K. Their electronic spectra were recorded and compared to the photoelectron spectra (PE.) of the neutral precursors. The results show that either the fourth or the fifth excited doublet state of the cations is of «Non‐Koopmans» type, with specific doublet energy (D) D (2Bg)=2.74 eV (1+), =2.59 eV (2+), =2.49 eV (3+). Remarkably, 1+ possesses two electronic states in the 2.7‐2.8 eV energy range: 2Au («Koopmans»‐type) and 2Bg («Non ‐Koopmans»‐type). The «SDT»‐equation \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm D} = \sqrt {{\rm S} \cdot {\rm T}} $\end{document} approximately connecting excited singlet (S) and triplet (T) states of a neutral alternant system with the excited doublet (D) states of its radical cation ‐ provided e‐promotion occurs For all three excited states between the same (paired) orbitals‐is satisfyingly exemplified by 1: S1 = 3.92 eV and T1= 2.06 eV for 1, D4 or 5=2.74 eV for 1+.
Die Struktur des Curare‐Alkaloides Calebassinin‐1 183. Mitteilung uber organische Naturstoffe
Authors: Guggisberg Armin , Prewo Roland , Bieri Jost H. , Hesse Manfred
Published: December 2004

The Structure of the Calabash Curare Alkaloid Calebassinine‐1

The quaternary alkaloid calebassinine, isolated 1947 from Calabash Curare. has now been separated into calebassinine‐1 and ‐2. X‐ray structure determination of calebassinine‐1 led to structure 2 with relative configuration. A possible biogenetic pathway from 2,16‐dihydroakuammicine (3) as well as its pyrolytic decomposition to 3‐ethylpyridine (9), the quinoline derivative 8, methylchloride and norcale bassinine‐1 are discussed.
Aspects of the Reduction of Double Bonds Using Cob (I)alamin as Catalys
Authors: Fischli Albert
Published: December 2004

The olefinic system in 3β‐methoxy‐4‐cholesten‐6 a‐ol (2) is reduced using cob (I)alamin (1(I); see Scheme 1) as catalyst, aqueous acetic acid as solvent and metallic zinc as electron source (cf. Schemes 2 and 3). Experimental evidence for an attack of 1(I) on both faces of the double bond is presented. By the same catalyst (1 R)‐10, 10‐dimethyl‐2‐pinene‐ 10‐carbonitrile (9) is first transformed to the menthene derivative 11 (see Schemes 4 and 5). The ring opening is then followed by a fast saturation of the disubstituted olefinic system in 11, and ultimately the remaining double bond is reduced in a slow reaction. The cis‐configurated saturated menthane derivative 16 is the main final product (16/17 ≈ 10:1).
Structural and Configurational Dependence of the Sensory Process in Steroids
Authors: Ohloff Günther , Maurer Bruno , Winter Beat , Giersch Wolfgang
Published: December 2004

Structural modifications of testosterone and 19‐nortestosterone have led to the synthesis of over 60 androstane and estrane derivatives whose sensory evaluation has allowed molecular parameters to be established for release of a ‘steroid‐type’ scent. Odor perception with O‐containing compounds in both classes has been found to be regioselective. Osmophoric groups at C(3) were found to be the most active and specific. Functionality at C(2) is accompanied to a large extent by anosmic defects, and O‐containing substituents at C(1) and C(4) appear to affect the receptor membrane in exceptional cases.

A further characteristic of the ‘steroid‐type’ scent is diastereoselectivity. The odor intensity of axial 2‐ and 3‐hydroxysteroids is far greater than that of the equatorial epimers, and epimeric hydroxy‐groups in the 1‐, 4‐, and 5‐positions lead to almost complete absence of odor. In addition, only steroids with ‘normal’ ring junctions and configuration were found to be odorants, whereas compounds with cis‐junctions between rings A and B, or C and D, were found to be practically inactive, Steroids therefore folow the ‘triaxial rule of odor sensation’.

The most remarkable feature of our findings with steroid odorants is enantioselectivity

The term ‘regioselective’ is currently used for a reaction in which formation of one structural (or positional) isomer is favored over another. For convenience we use ‘regioselective’, ‘diastereoselective’ or ‘enantioselective’ for substrate‐receptor interactions in which one positional isomer, diastereoisomer or enantiomer leads to a different sensory response (in quality and/or intensity) than another.

. Whereas with C
19
‐steroids of the ‘natural’ enantiomeric series the perception threshold is extremely low (<6 ppb), the corresponding ‘unnatural’ enantiomers have been found essentially odorless by a panel of 30 persons. This appears to be the first reported instance of a total enantioselective response to an odorant.
[2+2]‐Cycloaddition von Ketenen an «Maleinisoimide» und Überführung der spiroverknüpften b̃‐Laktame in Muconsäure‐ und Tetramsäurederivate
Authors: Capraro Hans‐Georg , Martin Pierre , Winkler Tammo
Published: December 2004

[2+2]‐Cycloaddition of ‘Maleic Isoimides’ with Ketenes and Reactions of Spiro‐b̃‐lactams to Muconic and Tetramic Acids

The [2 + 2]‐cycloaddition of iminolactones of type 2 (‘maleic isoimides’) with various ketenes affords spiro‐b̃‐lactams 4–6. These highly functionalized compounds react with CH3ONa giving ketoadipinic acid derivatives 12 and/or pyrrolidinediones 7, depending on the reaction temperature and the nature of substituents.
Total Synthesis of (±)‐α‐Acoradiene via Intramolecular Photoaddition and Reductive Cyclobutane Cleavage
Authors: Oppolzer Wolfgang , Zutterman Freddy , Bättig Kurt
Published: December 2004

(±)‐α‐Acoradiene (4) has been synthesized from 3‐methoxy‐2‐cyclohexenone by a sequence of 8 steps. The key steps (Scheme 6) are the regio‐ and stereoselective photo[2+2]addition 7→6 and the reductive fragmentation 6→5.
The Synthesis of Some 1, 8‐Phenanthrolines and Related Compounds
Authors: Markees Diether G.
Published: December 2004

The synthesis of ethyl 4‐oxo‐1, 4‐dihydro‐1, 8‐phenanthroline‐3‐carboxylate (2a) and some other 1, 8‐phenanthrolines is reported. The ethylation of the above ester yields a thermochromic product 2b and some ethyl 4‐ethoxy‐1, 8‐phenanthroline‐3‐carboxylate (3b). Reexamination of similar ethylations of analogous esters derived from 1, 7‐phenanthroline and 1, 10‐phenanthroline indicated formation of the O‐ethyl derivative of the former and the N‐ethyl derivative of the latter.
Anwendung der α‐Alkinon‐Cyclisierung: Totalsynthese von (±)‐Alben
Authors: Manzardo Giuseppe G. G. , Karpf Martin , Dreiding André S.
Published: December 2004

Application of the α‐Alkynone Cyclization: Total Synthesis of (±)‐Albene

A synthesis of the racemic form of the natural tricyclic hydrocarbon albene (1) from the Diels‐Alder adduct 2 of tiglyl chloride and cyclopentadiene is described (24% yield). The key step 5→6 involves a thermal α‐alkynone cyclization (Scheme 3), which is able to establish a new quarternary C‐atom at an unactivated position with a high degree of regiospecificity.
Synthesis and Photochemical Behaviour of 2‐Amino‐1,3‐Cyclohexadienes
Authors: Kilger Ralf , Margaretha Paul
Published: December 2004

The reaction of the 4,4‐dialkylated 2‐cyclohexenones 1 or 2 with a twofold excess of a secondary amine 3 affords the 2‐amino‐1,3‐cyclohexadienes 4 and 5, respectively. Irradiation (λ ≧ 300 nm) of the morpholino derivative 4a yields a mixture of the isomeric 3‐morpholino‐6‐methyl‐1,3,5‐heptatrienes 6 and 7, while 5 gives only one corresponding product 8. The reaction of enone 1 with an equimolar amount of pyrrolidine (3c) affords the bis‐enamine 9 which is converted to the unsaturated diketone 10 by oxidative hydrolysis.
Platin(II)‐Chromophore mit σ‐gebundenen Ligatoratomen
Authors: Kozelka Jiří , Ludwig Werner
Published: December 2004

Platinum(II) Chromophores with σ‐Bonded Ligating Atoms

The absorption spectra of the platinum(II) complexes PtLxL′4−x (L = NH3, amine, hydride, alkyl; L′ = trialkylphosphine) consist of three band systems: (i) ligand‐field bands, partially of fully screened by more intensive absorptions; (ii) at least three comparatively sharp bands of low to intermediate intensity (ϵ = 400–10000), which are assigned to Rydberg transitions from 5d(Pt) to a linear combination of the (n+1)s‐orbitals of the ligands (with a contribution of metal 6s‐ or 6p‐orbitals, respectively); (iii) (only in the case of chromophores with two phosphorus ligands in trans‐position) one high intensity band (ϵ = 20000–50000), presumably due to a transition from the asymmetric linear combination of the trans‐lying phosphorus lone‐pairs to 5dx2−y2(Pt). There is no evidence of low‐lying π‐combinations of phorphorus 3d‐orbitals in the absorption spectra.