bluuebunny/crossref_metadata_2025 huggingface dataset:
Nucleophilic Aromatic Substitutions. Part XIV.. Investigation of the mechanism of hydroxy‐denitration of 4,2‐and 2,4‐chloronitrobenzenediazonium ions as a function of pH
Authors: Pikulik Ivan I. , Weber Rudolf U. , Zollinger Heinrich
Published: December 2004

4,2‐Chloronitrobenzenediazonium ions in aqueous buffer solutions between pH 2.9 and 7.9 do not hydrolyze by dediazoniation as previous authors have assumed, but by denitration. The isomeric 2,4‐compound reacts by denitration (ca. 70%) and dechlorination (ca. 30%). The reactions are general base catalyzed. The products and kinetics are consistent with an SNAr‐mechanism in which the general base‐catalyzed addition of a hydroxyl group at the reacting C‐atom is rate‐limiting. The rate maxima at or near the pH‐values corresponding to (pK1 + pK2)/2 of the diazonium ⇄ cis‐diazotate equilibria can be rationalized on the assumption that the diazonium ion is the only equilibrium form of the diazo compound which enters the substitution proper, and the superposition of the rate term kB[B] of all nucleophiles involved (H2O, OH− and buffer bases).
Laser Flash Photolysis of Phthalocyanines in Solution and Microemulsion
Authors: Jacques Patrice , Braun André M.
Published: December 2004

Triplet state formation (Φisc) and properties (εT‐T, τT) of phthalocyanine (HPC) and zinc phthalocyanine (ZnPC) have been characterized in homogeneous solutions (1‐chloronaphthalene, 1‐propanol) and in microemulsion by investigating the variation of the transient optical density as a function of the intensity of the exciting laser. Experimental results follow the theoretically predicted dependence only for very low intensities of the exciting pulse. At higher intensities, a more complicated scheme of primary reactions has to be taken into account, implicating qualitative restrictions in the application of saturation experiments. The observed transients at high‐intensity excitation are interpreted as being perturbed by aggregational phenomena.
The structure of covalent hydrates of alloxazines. A reinvestigation
Authors: Koziol Jacek , Tyrakowska Bozena , Müller Franz
Published: December 2004

It is shown by 13C‐NMR. and synthesis of 6,7‐dimethyl‐3‐ethoxycarbonylamino‐quinoxaline‐2‐carboxamide (5) and methyl 6,7‐dimethyl‐3‐(N′‐methylureido)‐quinoxaline‐2‐carboxylate (6) that hydrolysis of lumichrome (1, R = H) must yield 6,7‐dimethyl‐3‐ureidoquinoxaline‐2‐carboxylic acid (2, R = H) and not 6,7‐dimethyl‐2‐oxo‐1,2,9,9a‐tetrahydrooxazolo[4,5‐b]quinoxaline‐9a‐carboxamide (2a, R = H), as previously proposed.
Kettenverlängerung funktionalisierter Alkanone durch Umlagerung
Authors: Lorenzi‐Riatsch Annalaura , Nakashita Yoshihiko , Hesse Manfred
Published: December 2004

Chain Expansion of Functionalized Alkanones by Rearrangement Reactions

In analogy to the transamidation reactions which were published earlier a method is described to prolong aliphatic C‐chains by two or four C‐atoms. 1,3‐Diketones or 2‐nitro alkanones which are monosubstituted at C(2) are condensed with e.g. methyl vinyl ketone. The reaction product is transformed to its chain‐prolonged isomer in the presence of strong base via a 4‐ or 6‐membered intermediate. The most effective reagent for the Michael reaction is methyl 3‐oxo‐4‐pentenoate (20). In this case it was possible to convert 3‐nitro‐2‐butanone (21) to methyl 2‐acetyl‐6‐nitro‐3‐oxoheptanoate (26) in 82% yield.
PCILO and CD. Conformational study of sulpiride, a dopamine antagonist
Authors: van de Waterbeemd Han , Testa Bernard
Published: December 2004

The conformational behaviour of sulpiride has been investigated by the quantum mechanical PCILO method and by CD. measurements. The results indicate the predominance of a folded, intramolecularly H‐bonded conformer, with extended conformers being only slightly less stable. The pharmacological relevance of these results is briefly discussed.
14‐Hydroxytaxodion als Hauptditerpen in Plectranthus grandidentatus GÜRKE; Isolierung von sieben neuen dimeren Diterpenen aus P. grandidentatus, P. myrianthus BRIQ. und Coleus carnosus HASSK.: Strukturen der Grandidone A, 7‐Epi‐A, B, 7‐Epi‐B, C, D und 7‐Epi‐D
Authors: Uchida Masaaki , Miyase Toshio , Yoshizaki Fumihiko , Bieri Jost H. , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Isolation of 14‐Hydroxytaxodione from Plectranthus grandidentatus GÜRKE and of Seven New Dimeric Diterpenoids from P. grandidentatus, P. myrianthus and Coleus carnosus Structures of Grandidone A, 7‐Epi‐A, B, C, D and 7‐Epi‐D

From the leaf‐glands of the title plant the following abietane diterpenes have been isolated and their structures established by chemical, spectroscopical and X‐ray methods: 14‐hydroxytaxodione (5, 0,57%), new as a natural product, the already known coleons U (6, 0,17%) and V (7, 0,024%), and furthermore 7 novel dimeric compounds named grandidones (ca. 0,09%), Both grandidone A (1a) and 7‐epigrandidone A (1b) as well as grandidone B (2a) and 7‐epigrandidone B (2b) are C(7) acetals of 6, 7‐Dioxoroyleanone with catecholes such as coleon U (→ 1a, 1b) or coleon V (→ 2a, 2b). Based on the relative configuration at C(7) of 1a which was established by X‐ray analysis, the constitutions of 1b, 2a and 2b were assigned by HPLC. ‐ controlled interconversions. The unstable grandidone C (3) is a C(7)‐C(7′) linked bis‐6‐oxoroyleanone with C2‐symmetry. Grandidone D (4a) and 7‐epigrandidone D (4b) are spiro‐dihydrofurans formed from 3 via a hypothetical bis (14‐hydroxytaxodione) by intramolecular addition of HO‐C(14) or HO‐C(14′) to C(7′) to C(7′) or C(7). The relative configuration of 4a was established by X‐ray analysis of its diacetate 4c. The absolute configuration of all dimers was established by the partial syntheses from 14‐hydroxytaxodion (5) (entirely described in the following communication).
Reactions of 2‐Diisopropylamino‐3, 7‐dehydrotropone: Conversion to the thione and dimerization
Authors: Gray Robert W. , Dreiding André S.
Published: December 2004

Reaktionen von 2‐Diisopropylamino‐3, 7‐dehydrotropon: Umwandlung in das Thion und Dimerisierung

Behandlung von 2‐Diisopropylamino‐3, 7‐dehydrotropon (1) mit Phosphorpentasulfid ergab 2‐Diisopropylamino‐3, 7‐dehydrotropothion (2). Mit Trifluoressigsäure entstand aus 1 ein stabiles Dimeres (5), das ein Dehydrotropon‐ sowie ein Tropon‐Ringsystem enthält. Die Strukturen von 2 und 5 ergeben sich aus ihren Spektraleigenschaften.
Iridoid and Aryl Glucosides from Globularia nudicaulis and Globularia nana
Authors: Chaudhuri Ratan K. , Salama Osama , Sticher Otto
Published: December 2004

The iridoid and aryl glycosidic constituents of Globularia nudicaulis L. and G. nana LAM. are reported. The structure determination of lytanthosalin (10‐O‐(E)‐cinnamoylaucubin), a new acylated iridoid glucoside, isolated from the latter species, is described.
Photoisomerization of Phenylazoalkenes
Authors: Schantl Joachim G. , Margaretha Paul
Published: December 2004

(E)‐Phenylazocyclohexene (1) undergoes photoisomerization to s‐cis‐(Z)‐phenylazocyclohexene (2). Compound 2 reisomerizes to 1 at room temperature.
Nucleosides and Nucleotides. Part 18. p‐nitrobenzenesulfonyl nitroimidazole as a new condensing agent in the triester synthesis of oligonucleotides
Authors: Leach Colin A. , Waldmeier Felix , Tamm Christoph
Published: December 2004

p‐Nitrobenzenesulfonyl nitroimidazole (p‐NBSNI) (5) has been shown to be an efficient and convenient condensing agent in the coupling of protected nucleotide fragments. Its utility has been demonstrated by a direct comparison with previously‐described condensing agents in the synthesis of various di‐ and tetradeoxy‐nucleotides.
Ru‐Catalyzed Oxidation of Acetylenes to α‐Diketones with Iodosylbenzene
Authors: Müller Paul , Godoy José
Published: December 2004

Disubstituted acetylenes are oxidized with PhIO in presence of Ru‐catalysts to afford α‐diketones in 65–85% yield. Under the same conditions terminal acetylenes are cleaved to carboxylic acids.
Structure‐Activity Relationship of Oxygenated Morphinans. V. Narcotic agonist and antagonist activity in the 14‐hydroxymorphinan series. Preliminary communication
Authors: Schmidhammer Helmut , Jacobson Arthur E. , Atwell Louise , Brossi Arnold
Published: December 2004

The synthesis of several 14‐hydroxymorphinans, using oxymorphone (= 3, 14‐dihydroxy‐4,5‐epoxy‐N‐methylmorphinan‐6‐one, 1) as starting material, is described. The antinociceptive potency of the N‐methyl substituted 14‐hydroxy‐morphinans was determined. Thus, in order of antinociceptive potency, 14‐hydroxy‐4‐methoxy‐N‐methylmorphinan‐6‐one (5) >4,5‐epoxy‐14‐hydroxy‐N‐methyl‐morphinan‐6‐one (3)>4, 14‐dihydroxy‐N‐methylmorphinan‐6‐one (4)>14‐hydroxy‐4‐methoxy‐N‐methylmorphinan (11) ≈4, 14‐dihydroxy‐N‐methylmorphinan (12). The most potent compound in this series, 14‐hydroxy‐4‐methoxy‐N‐methyl‐morphinan‐6‐one (5), was found to have about six times the potency of morphine; it was equipotent with levorphanol.
Correct Structure of a Condensation Product C6H12N4O4 from Hydrazine, Formaldehyde and Hydrogen Peroxide
Authors: Whittleton Stephen N. , Seiler Paul , Dunitz Jack D.
Published: December 2004

The compound mentioned in the title is shown by X‐ray analysis to be 1, 2, 7, 8‐tetraaza‐4, 5, 10, 11‐tetraoxatricyclo [6.4.1.12, 7] tetradecane, contrary to previous suggestions. The torsion angle about the peroxo bonds in the seven‐membered rings in 100°, close to the value in hydrogen peroxide, which would not be possible in a six‐membered ring.
Synthesis and biological properties of p‐azidophenylalanine13‐β‐melanotropin, a potent photoaffinity label for MSH receptors
Authors: Eberle Alex N. , De Graan Pierre N. E. , Hübscher Willy
Published: December 2004

p‐Azidophenylalanine13‐α‐melantropin ([Pap13]‐α‐MSH) was synthesized in homogeneous solution by the fragment condensation method, and its biological activity was determined in three different assay systems. The pigment‐dispersing activity relative to α‐MSH was 65%, measured with melanophores of Rana pipiens or of Xenopus laevis tadpoles. The tyrosinase‐stimulating activity was 50%, determined with cultured mouse melanoma cells. UV. irradiation of solutions containing ≤10−4M[Pap13]‐α‐MSH at 338 nm (intensity: 10−3 W · cm−2) led to complete photolysis of the photolabel within <20 min. Under these conditions [Pap13]‐α‐MSH was covalently inserted into MSH‐receptors which produced a longlasting pigment dispersion in Xenopus melanphores (see [3]). The extent of this prolonged stimulation depended on the hormone concentration used during photolysis. 1.8·10−9M [Pap13]‐α‐MSH which produced a full initial response failed to prolong the effect, whereas 1.2·10−8M hormone caused irreversible stimulation. It appears that only about 10% of the initially occupied receptors were covalently labelled because the log dose response curve was shifted to ∼ 10x higher concentration after a 200 min wash period: EC50 immediately after photolysis was 6 · 10−10M; after 200 min EC50 increased to ∼8·10−9M.
Dediazoniation of Arenediazonium Ions. Part XX. Secondary deuterium isotope effects in reactions of benzenediazonium tetrafluoroborate
Authors: Szele Ivanka , Zollinger Heinrich
Published: December 2004

Secondary deuterium isotope effects were measured for the dediazoniation of [2,4,6‐2H3]‐benzenediazonium tetrafluoroborate ([2H3]‐1), and were found to be (kH/kD3)s = 1.46 in 2,2,2‐trifluoroethanol (TFE) and 1.51 in 1, 1, 1, 3, 3, 3‐hexafluoro‐2‐propanol (HFIP), respectively. These values are in agreement with the previously proposed rate determining formation of the phenyl cation (Eqn. 1), and are similar to the results obtained by Swain et al. in other solvents. The Nα‐Nβ rearrangement Eqn. 2) of β‐15N labelled 1 was studied in TFE. The percent of rearrangement after 70% dediazoniation was found to be 8.18, which corresponds to a rate constant for the rearrangement kr=4.02 · 10−6S−1. Thus the secondary deuterium isotope effect in the rearrangement in TFE (kH/kD3)r was calculated to be 1.42. The fact that the isotope effect in the rearrangement is, within experimental error, the same as that observed during dediazoniation, definitely excludes the formation of benzenespirodiazirine cation 3, which has repeatedly been discussed as an intermediate in the rearrangement. The size of the deuterium isotope effect in the rearrangement is in accordance with the rearrangement proceeding via a phenyl cation/N2 molecule pair (2).
Trennung und Charakterisierung von β‐Carotin‐Isomeren
Authors: Vecchi Max , Englert Gerhard , Maurer Res , Meduna Vladimir
Published: December 2004

Separation and Characterization of the cis‐Isomers of β,β‐Carotene

A stable HPLC. system is described allowing the excellent separation of 11 different cis‐isomers of β,β‐carotene from the all‐trans compound. The system is applied to the analysis of cis/trans mixtures obtained from plant extracts and by photoisomerization of the all‐trans isomer. Al2O3 is used as the stationary phase while hexane with controlled H2O content is utilized as the mobile phase. With the aid of the optimum conditions 8 sufficiently stable cis isomers were isolated and their structures shown to be the 9‐, 13‐ and 15‐cis, the 9,9′‐, 9, 13‐, 9, 13′‐ and 13,13′‐di‐cis and, tentatively, the 9,13,13′‐tri‐cis β,β‐carotenes by application of 270‐MHz‐FT.‐1H‐NMR. spectroscopy.
The mass spectra of organic compounds. 6th Communication.. The Ring Opening Reaction of Isomeric Cyclanones C8H14O\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{+ \atop \dot{}} $\end{document} in metastable and collisional‐activation spectra
Authors: Gäumann Tino , Schwarz Helmut , Stahl Daniel , Tabet Jean‐Claude
Published: December 2004

The molecular ions from three isomeric cyclanones isomerize to the ethyl‐2‐cyclohexanone ion prior to C2H4 elimination. With D‐ and 18O‐labelled compounds it is shown by Mass Analyzed Ion Kinetic Energy Spectroscopy (MIKES.) that both isomerization and C2H4 loss are specific processes. By high resolution collisional activation spectra it is shown that the resultant fragment ion [C6H10O]\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{+ \atop \dot{}} $\end{document} (m/z = 98) differs in structure from the cyclohexanone molecular ion.
Asymmetric induction in Diels‐Alder reactions to acrylates derived from chiral sec‐alcohols. Preliminary communication
Authors: Oppolzer Wolfgang , Kurth Mark , Reichlin Daniel , Chapuis Christian , Mohnhaupt Martin , Moffatt Frank
Published: December 2004

Starting from the enantiomerically pure monoterpenes (+)‐pulegone (3), (+)‐limonene (7), (−)‐β‐pinene (9), (+)‐ and (−)‐camphor (13) or (+)‐cholestenone (11) the chiral alcohols 4, 5, 6, 8, 10, 12, 14, 15, 16, 17 et 18 were prepared; their acrylates II underwent a TiCl4‐promoted Diels‐Alder addition to cyclopentadiene (Scheme 3, Table) giving in a predictable manner either the (2R)‐ or the (2S)‐adducts III with 63 to 88% asymmetric induction.
Synthesis and Absolute Configuration of New Trichloro Steroids with Cyclopropane‐Containing Side Chains
Authors: Lang Robert W. , Djerassi Carl , Strong Phyllis D. , Swenson Dale C. , Duax William L.
Published: December 2004

The determination of the absolute configuration of the trichloro steroids 2a and 2c (cf. Scheme 1) by means of two X‐ray crystal structure analyses is reported and applies also to the determination of the absolute configurations of several derived steroidal cyclopropanes [1]. The preparation of the chlorinated derivatives 2a‐c is described and the spectroscopic properties of 1 and 2 are summarized.
Lipophilic Synthetic Monoamides of Dicarboxylic Acids as Ionophores for Alkaline Earth Metal Cations
Authors: Maj‐Zurawska Magdalena , Erne Daniel , Ammann Daniel , Simon Wilhelm
Published: December 2004

N, N‐Dioctadecyl‐substituted lipophilic monoamides of certain dicarboxylic acids have been prepared. It is shown that they induce a transport of alkaline earth metal cations through solvent polymeric membranes coupled to a counter transport of hydrogen ions or K+. They proved to be suitable components for ion‐selective electrodes.
Strukturaufklärung eines Dimethylfulven‐Trimeren. Hinweis auf eine [6 + 4]‐Cycloaddition von 6, 6‐Dimethylfulven
Authors: Uebersax Beat , Neuenschwander Markus , Engel Peter
Published: December 2004

Structure Elucidation of a Dimethylfulvene‐trimer. Evidence for a [6+ 4]‐Dimerization of 6, 6‐Dimethylfulvene

Thermal reaction of pure 6, 6‐dimethylfulvene (1c) at 60° gives an oligomeric mixture consisting mainly of fulvene‐trimers. The structure of the main product 3c is partially elucidated by 1H‐NMR. investigations at 400 MHz and definitely confirmed by X‐ray analysis. The formation of 3c is explained in terms of a [6+4] dimerization, followed by a 1, 5‐proton‐shift and a final Diels‐Alder reaction.
Total Synthesis and Electrophysiological Properties of Natural (−)‐Perhydrohistrionicotoxin, its Unnatural (+)‐Antipode and their 2‐Depentyl Analogs
Authors: Takahashi Kimio , Witkop Bernhard , Brossi Arnold , Maleque Mohammed A. , Albuquerque Edson X.
Published: December 2004

Natural (−)‐perhydrohistrionicotoxin (6a), its unnatural (+)‐antipode 6b, (−)‐2‐depentylperhydrohistrionicotoxin (7a) and its (+)‐antipode 7b have been prepared and characterized. Kishi's lactam 8 reacted with optically active iso‐cyanates, and the mixture of diastereomeric carbamates so obtained was separated and hydrolyzed yielding the optical antipodes of Kishi's lactam in optically pure form. Reduction with LiAlH4 yielded the optically active 2‐depentyl analogs, while another sequence already developed in the racemic series afforded the natural toxin and its (+)‐antipode. Some electrophysiological properties of these compounds are presented.
Stoffwechselprodukte von Mikroorganismen. 211. Milteilung. Röntgenstrukturanalyse von Elaiophylin
Authors: Neupert‐Laves Katarina , Dobler Max
Published: December 2004

The X‐ray crystal structure analysis of the antibiotic elaiophylin (1), monoclinic, a = 9.927, b = 10.105, c = 31.183 Å, β = 93.20°, space group P21, confirms the constitution elucidated by spectroscopic methods and chemical degradation. In the crystal the two chemically equivalent halves of the molecule are related by an approximate twofold rotation axis.
The Reaction of 3‐Formylchromone with ortho‐Substituted Anilines. Preparation of a Tetraaza [14]annulene
Authors: Sigg Ivo , Haas Georges , Winkler Tammo
Published: December 2004

The reactions of 3‐formylchromone (1) with 1, 2‐phenylenediamine, 2‐amino‐diphenylamine and 2‐aminophenol were reinvestigated and shown to yield 1, 8‐dihydro‐6, 13‐di (2‐hydroxybenzoyl)‐dibenzo [b, i]‐l, 4, 8, 11‐tetraazacyclotetradeca‐ 4, 6, 11,13‐tetraene (7), 3‐[2‐(1‐phenyl)benzimidazolyl]chromone (10b) and 3‐(2‐hydroxyphenyl)iminomethylchromone (4), respectively at variance with earlier reports. Compound 4 reacts with ethanol to give 2‐ethoxy‐3‐[(2‐hydroxyphenyl)‐aminomethylidene]chroman‐4‐one (5b). Dehydrogenation of 7 produces 3‐(2‐benz‐imidazolyl)chromone (10a), also at variance with earlier reports. The structures have been elucidated with the aid of NMR. and mass spectra. The reaction mechanism is discussed.
On the Absolute Configuration of (+)‐Indane‐1‐carboxylic Acid
Authors: Hansen Hans‐Jürgen , Slewka Hans‐Richard , Hug Werner
Published: December 2004

The (R)‐configuration, attributed to (+)‐indane‐1‐carboxylic acid ((+)‐1) by Fredga [1], is unequivocally confirmed (Scheme 1). Configurational doubts, raised by an erroneous ORD. curve of (−)‐1‐methylindane ((−)‐4) published by Brewster & Buta [2], are unfounded (cf. the following paper of Brewster[3] and the corrections in (4)). This was further verified by preparing deuteriated 1‐methylindanes starting with (−) (R)‐3‐phenylbutyric acid ((−)‐(R)‐5) as well as with (+)‐(R)‐1 or (−)‐(S)‐1 (Scheme 2). The ORD. curves of the optically active 4 thus obtained were (disregarding deuteri‐um isotope effects) identical or antipodal, respectively (of. Fig. 1, 2, and 7a–e).

Optically active methyl indane‐1‐carboxylates ((−)‐(R)‐14 or (+)‐(S)‐[l‐2H]‐14) show a strong solvent dependence of their ORD. and CD. spectra with a sign inver‐sion occuring in going from isooctane to methanol or benzene. The observed changes can be explained by a change in the population of conformations where the ester carbonyl group is eclipsed either with the C(1), C(2)‐ or C(1), H‐bond, with the n, π* ‐transition having a slightly different energy and the ester group an essentially enantiomeric environment with respect to its orientation relative to the benzene moiety.
Zum stereochemischen Verlauf der Biosynthese von 2‐Oxo‐pantolacton: Synthese von stereospezifisch indiziertem Pantolacton aus Äpfelsäure
Authors: Wasmuth Daniel , Arigoni Duilio , Seebach Dieter
Published: December 2004

(+)‐Pantolactone1 (13) has been synthesized from (−)‐(S)‐dimethyl malate (7) in 40% yield in a short sequence involving double alkylation (7 → 10 → 11), selective hydrolysis (11 → 12) and subsequent reduction (12 → 13). Through variation of the alkylating agents and preparation of the two diastereomeric 3‐ethyl‐3‐methyl malates 14 and 15 it was possible to show that the diastereoselectivity of the second alkylation step is brought about by preferential attack from the Re‐face of the critical enolate (9, see also Scheme 1). This knowledge, in turn, has been exploited for the synthesis of a sample of pantolactone specifically enriched with 13C in its Si‐methyl group. Analysis of the 13C‐NMR. spectrum of this sample together with the results of biosynthetic experiments previously reported by Aberhart demonstrates that the biological hydroxymethylation of 2‐oxoisovaleric acid (3) to 2‐oxopantoic acid (4), an important step in the biosynthesis of pantothenic acid, takes place in a retention mode (of. Scheme 2).
Synthesis of optically pure compounds by enantiotopically differentiating monoacetalization of prochiral diketones
Authors: Duthaler Rudolf O. , Maienfisch Peter
Published: December 2004

Reaction of 9‐methyl‐cis‐decalin‐1,8‐dione (2) and of its trans‐isomer (3) with (2R,3 R)‐2,3‐butanediol (8) gives in both cases the monoacetals in high yield. While no enantiotopic differentiation is found for 3, a strong preference for the (9S,10 R)‐monoacetal 9 is found for the cis‐decalin‐dione 2. The differentiation, reaching a maximal ratio of 9:1, is found to increase by conditions, which slow down the rate of reaction, e. g. lowering the temperature, the concentration of the acid catalyst, or by using a sterically encumbered catalyst. The use of this procedure for the preparation of optically active compounds is exemplified by the transformation of monoacetal 9 (obtained in 76% yield from 2) into (9 R, 10 R)‐9‐methyl‐1‐decalone (12). The differing behaviour of diketones 2 and 3 is discussed in terms of steric and electronic effects.
Intramolecular Carbonyl Group Site Exchange in Symmetrically Substituted (n‐1, 3‐Diene)tricarbonyliron Complexes Short Communication
Authors: Bischofberger Pius , Hansen Hans‐Jürgen
Published: December 2004

Activation parameters have been determined for the intramolecular site exchange of the carbonyl groups in tricarbonyliron complexes of 1,4‐ and 2,3‐disubstituted 1,3‐butadienes, of 1,3‐cycloalkadienes and of 1,2‐dimethylidene‐cycloalkanes by temperature‐dependent 13C‐NMR. spectroscopy (see Table 1). The variations of the activation parameters are discussed in terms of a turnstile‐type mechanism for the exchange process and of the differences in the ground state and transition state stability of the complexes. A VB‐model of the complexes is used to explain the difference in the stabilities.
Face Selectivity of the Diels‐Alder Additions of Exocyclic Dienes Grafted onto 7‐Oxabicyclo[2.2.1]heptanes
Authors: Mahaim Cyril , Vogel Pierre
Published: December 2004

Stereoselective syntheses of 2exo, 3exo‐bis (chloromethyl)‐5‐[(Z)‐chloromethylidene]‐ (9), 2exo, 3exo‐bis (chloromethyl)5‐[(E)‐chloromethylidene]‐ (10) and 2exo, 3exo‐bis(chloromethyl)‐5‐[(E)‐methoxymethylidene]‐6‐niethylidene‐7‐oxa‐bicyclo[2.2.1]heptane (13) are presented. Double elimination of HCI from 9, 10 and 13 yielded 2‐[(Z)‐chloromethylidene]‐ (14), 2‐[(E)chloromethylidene]‐ (15) and 2‐[(E)‐methoxymethylidene]‐3,5,6‐mmethylidene‐7‐oxabicycio[2.2.1]heptane (18), respectively, without loss of the olefin configuration. Ethylene tetracarbonitrile (TCE) and N‐phenyltriazolinedione (NPTAD) added to these new exocyclic dienes and tetraenes preferentially onto their exo‐face. The same face selectivity was observed for the cycloadditions of TCE to the (Z)‐ and (E)‐chlorodienes 9 and 10, thus realizing a case where the kinetic stereoselectivity of the additions is proven not to be governed by the stability of the adducts. The exo‐face selectivity of the Diels‐Alder additions of dienes grafted onto 7‐oxabicyclo [2,2.1]heptanes contrasts with the endo‐face selectivity reported for a large number of cycloadditions of dienes grafted onto bicyclo[2.2.1]heptane skeletons.
Synthese und Circulardichroismus optisch aktiver Carotinoidmodelle
Authors: Buchecker Richard , Marti Urs , Eugster Conrad Hans
Published: December 2004

Synthesis and Circular Dichroism of Optically Active Carotenoid Models

The synthesis of the following optically active carotenoidic model compounds are described: (—)‐(3,S,3′S)‐3,3′‐diisopropenyl‐16,17,18,16′,17,18′‐hexanor‐β,β‐carotene (1), (3R,3′R)‐19,20,19′,20′‐Metranor‐zeaxanthin (2) and (6R,6′R)‐19,20, 19′,20′‐tetranor‐ε,ε‐carotene (3). These compounds were synthesized for the following reasons: (1) the presence of methyl groups at C(1), C(1′), C(5), C(5′) of cyclic carotenoids profoundly affects the torsional angle of the C(6), C(7)‐ and C(6′), C(7′)‐bonds. Sign and magnitude of this angle are, according to recent theories [4] [5], responsible for a helical chromophore and for strong conservative [4] Cotton effects. CD. measurements of 1 give experimental support to these state‐ 1 exhibits weaker and less temperature dependent Cotton effects. Of more significance, the shape of the curve is no longer conservative, as expected. This constitutes experimental evidence for the contention that the β‐endgroups and the polyene chain indeed form an inherently dissymmetric chromophore in optically active β, β‐carotene derivatives; (2) the slightly S‐shaped form of the polyene chain of carotenoids, shown by X‐ray analyses [12] [13], is mainly ascribed to the presence of the methyl groups in the chain. Models 2 and 3 therefore are assumed to be linear. CD. studies of these compounds should consequently give information about the influence of deviation from Linearity and planarity of the polyene on the CD. spectra of carotenoids. CD measurements of 2 and 3 show that the lack of methyl groups does not alter the general type of the curve. Only the intensity and to some extent the position of the Cotton effects are influenced. Carotenoids with the ε‐endgroup possess inherently symmetric but asymmetrically distorted chromophores.

The assumption that non‐conservative CD. spectra could become conservative upon cooling [4] is experimentally confirmed by model 3.

The rule stating that pairs of all‐(E) and mono‐(Z) isomers of carotenoids with only one cyclic endgroup should have CD. spectra with the same sign [5] is disproved by the CD. spectra of four stereoisomeric rubixanthins (s. Fig. 5).

The UV./VIS. spectrum of 3, λmax 447 (ε 216000), 418 (ε 189000) exhibits the highest molecular extinction ever reported for a carotenoid.
Polyamines XV. Thermodynamics of Metal Complex Formation of Linear Tetraamines Containing Two Ethylenediamine Residues
Authors: Anderegg Giorgio , Bläuenstein Peter
Published: December 2004

The complex formation of Co2+, Ni2+, Cu2+, Zn2+, Pb2+ and Hg2+ with three tetraamines of type H2N(CH2)2NH(CH2)nNH(CH2)2NH2 (= 2, n, 2‐tet) for n = 2. 3 and 4, and with N‐methylethylenediamine (= nmen) have been investigated at 25° and I = 1(KNQ3). The stability constants and the heat evolved by formation of the (1:1)‐complexes ML have been determined. It is shown that the more stable complexes are normally formed by 2,3,2‐tet‐ligands. These results are discussed relating the thermodynamic data obtained to the stereochemistry of the complexes and using the visible spectra of the complexes in solution. The change in enthalpy is found to be the dominant factor and the measure of the steric strain whereas the entropy of complex formation decreases slowly.
Eine neue, einfache Synthese von 2,3,5‐Trichlorpyridin
Authors: Steiner Eginhard , Martin Pierre , Belluš Daniel
Published: December 2004

A New Simple Synthesis of 2,3,5‐Trichlorpyridine

A simple synthesis of 2,3,5‐trichloropyridine by the copper‐catalyzed free radical addition of chloral to acrylonitrile with or without isolation of the primary 1:1 adduct,4‐formyl‐2,4,4‐trichlorobutyronitrile (1), is described.
Dimetallic Complexes with Bridging Seven‐membered Cycloolefins. Synthesis, Multinuclear NMR.‐Spectroscopic Properties and Structure
Authors: Salzer Albrecht , Egolf Thomas , Von Philipsborn Wolfgang
Published: December 2004

The synthesis of dimetallic olefin complexes of the type L1M1C7H7M2L2 (M1 = Fe, Co, Rh; M2 = Rh, Ir, Pd; L1 = CO, C5H5; L2 = diene, allyl, P(OR)3) is described. The fluxional structures were investigated by 13C‐, 57Fe‐ and 103Rh‐NMR.‐spectroscopy, and a cisoid dimetallic coordination, including a (metal, metal)‐bond, can be deduced for the C7H7‐ring. 57Fe‐ and 103Rh‐chemical shifts give indications for the charge distribution in the 34e‐complexes. The homodimetallic complex (Cp)Rh(tropone)Rh(Cp) (13, Cp = cyclopentadienyl) and the corresponding 2‐methoxytropone complex 14 were synthesized in addition to the above mentioned complexes. A fluxional bis(1‐3‐η‐allyl)‐coordination of the two Rh‐atoms was derived from the temperature‐dependent 13C‐NMR.‐spectra. A spin simulation of the (Cp)‐multiplets of 12 and 13 yields information about (Rh, Rh)‐spin‐coupling which amounts to ≈5 Hz at 30°.
Substituted 2‐Phenyl‐ and 2‐Cyclohexyl‐trans‐decalins, New Classes of Nematic Liquid Crystals
Authors: Petrzilka Martin , Schleich Kuno
Published: December 2004

Versatile procedures for the preparation of the title compounds are described. Representatives of ketones (12and27), hydrocarbons (19and28), acids (13), esters (15. and20), ethers (22) and nitriles (18) possess wide‐range nematic phases, provided their terminal chains R2and R3contain at least three methylene units.
A convenient and diastereoselective route to homoallyl alcohols: Addition of (z)‐ or (e)‐alkenyl‐dimethoxyboranes to aldehydes
Authors: Fujitta Katsuramaru , Schloser Manfred
Published: December 2004

(Z)‐2‐Butenyl‐dimethoxyborane adds smoothly to propanal and benzaldehyde to afford the homoallyl alcohols (R*,R*)‐1 and (R*,R*)‐2, In contrast (E)‐2‐butenyl‐dimethoxyborane leads to adducts having the (R*,S*)‐configuration. Dimethoxy‐(Z)‐2‐pentenylborane, dimethoxy‐(Z)‐(2‐methyl‐2‐butenyl)borane and (2Z,4E)‐or (2E,4Z)hexadienyl‐dimethoxyborane, treated with propanal, give (R*,R*)‐3, (R*,R*)‐4, (E),(R*,S*)‐5 and (Z),(R*, R*)‐5, respectively. A transition state model implying a pericyclic electron motion is in perfect agreement with the regio‐ and stereoselective outcome of these borane reactions.
The Synthesis of 5,11,17‐Trihalotetracyclo [13.3.1.13,7.19,13]henicosa‐1 (19),3,5,7 (20),9,11,13 (21), 15,17‐nonaene‐19,20,21‐triols and 5,11,17‐trihalo‐19,20,21‐trihydroxytetracyclo [13.3.1.13,7. 19,13]henicosa‐1 (19),3,5,7 (20),9,11,13(21), 15,17‐nonaene‐8,14‐dione [1]. Cyclo‐derivatives of Phloroglucide Analogues
Authors: Moshfegh Ali A. , Beladi Effat , Radnia Lida , Hosseini Afsaneh S. , Tofigh Soosan , Hakimelahi Gholam H.
Published: December 2004

The synthesis of the title compounds (1 and 3) is described. Some of the compounds prepared were found to be active against a number of pathogenic microorganisms in vitro. Structure‐activity relationship is briefly discussed.
Structural Analogues Of Aporphines Part 1: Synthesis of Apomorphines with the Catechol Moiety Replaced by 5‐membered Heterocycles
Authors: Berney Daniel , Schuh Karlheinz
Published: December 2004

Analogues of apomorphine (1) having the catechol moiety replaced by pyrrole (→10, 18), pyrazole (→12), isoxazole (→13, 14), thiazole (→16) and thiadiazole (→20) ring systems have been synthesized from the key intermediate ketone 6.
Thermal Isomerization of 7,8‐Diazabicyclo[4.2.2]deca‐2,4,7,9‐tetraene N‐oxide to Benzaldehyde Oxime
Authors: Olsen Henrik
Published: December 2004

Thermal transformation of 7,8‐diazabicyclo[4.2.2]deca‐2,4,7,9‐tetraene N‐oxide (3) was observed, (Z)‐benzaldehyde oxime being the major product, with (E)‐benzaldehyde oxime as a minor product. N‐Oxide 3 was labeled with deuterium α to the oxidized N‐atom. The location of the deuterium label in the thermolysis products fitted one of two reasonable mechanisms.
Photon‐Triggered Complex Formation: Radical Complexes of o‐Benzosemiquinone, Dopa, Dopamine and Adrenaline Formed by Electron‐Transfer Reaction from Excited Tris (2,2′‐bipyridyl)ruthenium (II)
Authors: Plancherel Dominique , von Zelewsky Alex
Published: December 2004

The pyrocatechol derivatives, dopamine (2), adrenaline (3) and L‐dopa (4) form in their semiquinoid oxidation states complexes with several closed‐shell metal ions like Zn2+, Cd2+ and Y3+. This complex formation can be triggered by visible light via a one‐electron transfer reaction from the pyrocatechol derivative to (3CT)Ru(bpy), which is thereby reduced (Schemes 1 and 2), The quenching of the triplet charge‐transfer state, (3CT)Ru(bpy) cannot be measured by conventional methods (Stern‐Volmer plot), because the bimolecular electron‐transfer rate is too slow (kq < 10−7 M−1 s−1). ESR. spectroscopy shows, however, clearly the paramagnetic reaction products. The concentration of these paramagnetic species is strongly enhanced by complex formation.

The hindered rotation of the side chain in L‐dopa and in its Y3+‐complex is described within a two‐jump model, which gives best agreement between calculated and measured spectra assuming an energy of 37 kJmol−1 for the rotational barrier.
Forward Electron Scattering in Benzene; Forbidden Transitions and Excitation Functions
Authors: Allan Michael
Published: December 2004

A systematic study of vibronic excitation in benzene via forward electron scattering was carried out using a novel type of a trochoidal electron spectrometer. Energy‐loss spectra in the energy range 1.0–9.5 eV, with residual energies 0.03–20 eV as well as excitation functions for individual vibrational levels of some of the triplet and singlet states are presented and discussed. Following observations were made. (1) A new s‐type Rydberg series with quantum defect δ = 0.86. (2) Additional information on the complex 6–6.5 eV band. (3) A new core excited shape resonance at 6.5 eV. (4) A narrow Feshbach resonance at 5.87 eV, The new spectrometer is suggested as a tool for routine study of forbidden transitions and negative ion states in organic molecules.
Preparation of 1,2exo‐ and 1,2endo‐Diiodo‐bicyclo[2.2.1]heptane
Authors: Camenzind Hugo , Krebs Ernst‐Peter , Keese Reinhart
Published: December 2004

1,2 exo‐Diiodo‐norbornane (4) was prepared from norcamphor hydrazone by oxidative iodination and subsequent rearrangement of the 2,2‐diiodo‐bicyclo [2.2.1]heptane (2). The stable α‐iodohydrazone 11 was obtained from 1‐iodo‐bicyclo[2.2.1]heptan‐2‐one (10), which itself was prepared from 1‐iodo‐norbornene (5). Subsequent treatment of 11 with iodine lead to 1,2,2‐triiodo‐norbornane (12) and l,2‐diiodo‐norborn‐2‐ene (13). 1,2 endo‐Diiodo‐norbornane (14) was obtained by stereoselective reduction of 12 with tribtityltinhydride or by reaction of 13 with diimide.
Solvent‐Induced Deuterium Isotope Effects in 13C‐ and 15N‐NMR. Spectra of Enaminones
Authors: Kozerski Lech , von Philipsborn Wolfgang
Published: December 2004

The effect of deuterium on the 13C and 15N chemical shifts of enaminones has been investigated. D/H isotope shifts are reported for neutral and protonated species, i.e., when the isotope is exchanged on the C(2)‐, N‐, or O‐atoms. In cases of slow exchange the isotope shifts were obtained from solutions containing both isotopomers, whereas for fast exchange (acidic solutions) either separate NMR. sample tubes (15N‐NMR.) or coaxial tubes (13C‐NMR.) were used.

In neutral molecules the isotope effects δC(D, H) are intrinsic in nature. In acidic solutions, the enaminocarbonyl cations formed exhibit δC(D, H)‐ and δN(D, H)‐values which are discussed in terms of the proton transfer. The mesomeric character of the cations is reflected by characteristic features in the δC(D, H)‐ and δN(D, H)‐values, which can be ascribed to isotopic perturbation of resonance.

O‐Protonation shifts in the 15N‐resonance, observed for the first time, are large and positive (+60 to +76 ppm), in contrast to amides, where the effects are of the same sign but an order of magnitude smaller. Both protonation shifts and solvent‐induced isotope effects are discussed in connection with the nucleophilic character of the reactive centers in the enaminone synthon.
Synthese von 1, 2‐annelierten 1, 4‐Benzodiazepinen und 4, 1‐Benzoxazepinen
Authors: Müller Werner , Stauss Urs
Published: December 2004

The syntheses of 1, 2‐annelated 1, 4‐benzodiazepines (IV, Y = N) and 4, 1‐benzoxazepines (IV, Y = 0) are described (Scheme 1). The key step is a nucleophilic aromatic substitution of 2‐substituted piperazines (II, Z = NCH3), piperidines (II, Z = CH2) or pyrrolidines (II, Z= (CH2)0) with activated aryl halides (I).
Nachweis von C (15)‐epimeren Coleonen C und D in der Natur und ihre Bedeutung für den sterischen Verlauf der Bildung des Spirocyclopropanrings
Authors: Rüedi Peter , Schmid Jean Martin , Eugster Conrad Hans
Published: December 2004

Natural Occurrence of C(15)‐Epimeric Coleons C and D and its Significance to the Stereochemistry of the Formation of a Spirocyclopropanring

In a previous paper some evidence was presented for a predominant occurrence of epimeric coleons ((15S)‐coleon C ((15 S)‐1a), and (15S)‐coleon D ((15S)‐2a)) in Plectranthus lanuginosus [1], The proposed structures have now been proven by careful comparison of their physical data with those of the already described C(15)‐epimers whose structures were deduced by X‐ray analysis of a derived cis‐diketone 3 [5], Examination of the epimeric purity of coleons possessing a 2‐hydroxy‐1‐methylethyl side‐chain (coleons C, D, H, I, I′ and derivatives) isolated from seven different species (Coleus, Plectranthus and Solenostemon) has shown that these coleons always occur as a mixture of C(15)‐epimers, although in most cases with one predominant epimer. The consequences for the stereochemistry of the postulated in vivo formation of the methyl‐substituted spirocyclopropane substructure is discussed.
Simplified Liquid‐Phase Preparation of Four Decadeoxyribonucleotides and their Preliminary Spectroscopic Characterization
Authors: Denny William A. , Leupin Werner , Kearns David R.
Published: December 2004

Four self‐complementary decadeoxyribonucleotides, dApTpApTpApTpApTpApT, dApTpApTpCpGpApTpApT, dApTpApTpGpCpApTpApT and dApApApApApTpTpTpTpT, were chemically synthesized by the phosphotriester procedure. Efforts were concentrated on keeping the procedure as simple as possible, concomitant with obtaining high‐purity products at each step of the process. The decamers were elaborated from the 3'‐end, starting with a 3'−O‐benzoylated monomer according to the scheme: monomer + monomer → dimer + dimer → tetramer + dimmer → hexamer + tetramer → decamer. Purity of intermediates and of the fully blocked decamers were monitored by chromatography and by 300‐MHz 1HN M R. spectroscopy. The deblocked decadeoxyribonucleotides were characterized by their UV., CD., and 1HNMR. spectra.
Structure‐Activity Relationship of Oxygenated Morphinans. VII. 5‐Methylated and 14‐Hydroxy‐substituted Agonists and Antagonists of the 4‐Hydroxy‐ and 3, 4‐Dioxygenated 6‐Morphinanone Series
Authors: Brossi Arnold , Atwell Louise , Jacobson Arthur E. , Rozwadowska Maria D. , Schmidhammer Helmut , Flippen‐Anderson Judith L. , Gilardi Richard
Published: December 2004

Several morphinanone agonists differently substituted at C(3), C(4), C(5) and C (14) and antagonists of the 4‐hydroxy and 3, 4‐dimethoxy series were prepared by conventional chemistry. It was demonstrated that the oxygenation pattern in the bay‐area, encompassing C(3) and C(4), is important. Alkylation at C(5) or hydroxylation at C(14) lowered the potency of the compounds. The most potent agonist was found to be the N‐phenethyl‐substituted ketone 27, which was six times more potent than morphine in the hot‐plate assay. The 3, 4‐methylenedioxy‐substituted ketone 9 was about 20 times less potent than its 3, 4‐dimethoxy congener. An X‐ray analysis of 9 and a representative agonist showed that the stereochemical features in the bay‐area were similar and could not be used to explain this difference.
Intramolecular Transfer of Excitation Energy, Complexation with Metal Ions, and Interactions with Liposomes of Cyclo [tryptophyl‐sarcosyl‐sarcosyl‐Nϵ‐dansyllysyl‐prolyl]
Authors: Kimura Shunsaku , Imanishi Yukio
Published: December 2004

A cyclic pentapeptide containing an energy donor group and an energy acceptor group within the molecule, cyclo [Trp‐Sar‐Sar‐Lys (DNS)‐Pro], was synthesized. Its conformation, complexation with metal ions, intramolecular energy transfer, and interaction with liposomes were investigated. The precursor, cyclo [Trp‐Sar‐Sar Lys (Z)‐Pro], contained one cis‐sarcosyl peptide bond and a β‐turn in which the Pro‐residue occupied the 3rd position. This cyclic pentapeptide formed a complex selectively with Ba2+ and its binding constant in 95% aqueous methanol solution was 2.0 × 103 1 · mol−1. The intramolecular energy‐transfer efficiency of cyclo [Trp‐Sar‐Sar‐Lys (DNS)‐Pro] was almost constant between − 60° and 40° in ethanol, while it increased at temperatures lower than 34° in liposomes as a result of the pre‐transition of the lipid assembly. On the other hand, the intramolecular energy transfer efficiency of cyclo [Trp‐Sar‐Sar‐Lys (DNS)‐Pro] decreased upon complexation with Ba2+.
Crystal Structure of Tetrakis (phenacetin) Dihydrogentetraiodide Dihydrate {[H5C2OC6H4N (H)C(CH3)O]4·H2I4·2H2O}
Authors: Herbstein Frank H. , Kapon Moshe , Schwotzer Willi
Published: December 2004

(Phenacetin)4·2I4·2H2O is triclinic, a = 13.641 (7), b = 12.807 (6), c = 7.201 (3) Å, α = 99.8 (4), b̃ = 86.5 (4), γ = 104.0 (5)°, P1, Z = 1. The ordered crystal structure has been refined to RF = 0.050, using 4173 independent reflections measured on a four‐circle diffractometer with MoKa (graphite monochromator) radiation. The crystals are composed of alternating positively and negatively charged slices; each positive slice contains a double layer of stacks of hemi‐protonated phenacetin molecules which are H‐bonded through their carbonyl groups (d(O ‐ ‐ ‐ O) = 2.432 (4) Å) while each negative slice contains a single layer of I2−4‐ions linked in chains along [100] through H‐bonds to pairs of water molecules. The axes of the phenacetin stacks are parallel to the planes of the (I2−4·2H2O)‐layers. The I2−4‐ion is centro‐symmetric and can be approximately represented as I−‐ ‐ ‐ I–I‐ ‐ ‐ I− (d(I− ‐ ‐ ‐ I) = 3.404 (1) Å; d(I–I) = 2.774 (1) Å). The compound is a pseudo‐type A basic salt.
Über die Reaktion 1,2‐disubstituierter Norbornane mit Dinatriumtetracarbonylferrat(‐II). Vorläufige Mitteilung
Authors: Camenzind Hugo , Vögeli Ulrich Christian , Keese Reinhart
Published: December 2004

Reductive elimination at 1,2exo‐diiodonorbornane (6) was induced by Collman's reagent. Surprisingly, 1,2endo‐diiodonorbornane (9) and 1‐iodo‐2endo‐trifluoromethylsulfonyloxy‐norbornane (10b) lead only to reactions of the substituent in 2‐position. Mechanistic aspects are related to the reactions of monosubstituted iodonorbornanes with Collman's reagent.
Rhodium‐Catalyzed C,C‐Double Bond Cleavage by Molecular Oxygen
Authors: Bönnemann Helmut , Nunez Washington , Rohe Dieter M. M.
Published: December 2004

Acetylacetonatorhodiumolefin systems, allylrhodium complexes, or (Ph3P)3RhCl catalyzed the conversion of alkenes and molecular oxygen to carbonyl compounds via CC‐bond cleavage. For example, 2,3‐dimethyl‐2‐butene was transformed into acetone. Butadiene and isoprene also undergo oxidative CC‐bond cleavage to form acrylaldehyde and related compounds.
Stoffwechselprodukte von Mikroorganismen. 219. Mitteilung. Versuche zur Strukturaufklärung von Niphimycin, 2. Teil. Die Konstitution von Desmalonyl‐niphimycin I
Authors: Keller‐Schierlein Walter , Joos Beda , Kaiser Hans‐Peter , Gassmann Peter
Published: December 2004

On the Structural Elucidation of Niphimycin, Part II. The Constitution of Demalonylniphimycin I

A stepwise degradation of copiamycin and niphimycin I with ozone and sodium periodate, partly combined with D‐labelling, and intense spectroscopic investigations of the degradation products led to the structural formulae 34 for demalonylcopiamycin (in agreement with the structure proposed by Iwasaki et al. for the same antibiotic) and 38 for demalonylniphimycin. The antibiotics copiamycin and niphimycin are half esters of malonic acid and the macrolide polyols 34 and 38, resp., with uncertain positions of the malonyl residues.
Synthesis of Enantiomerically Pure Substituted Cyclopentenes from (−)‐Quinic Acid
Authors: Barrière Jean‐Claude , Cléophax Jeanine , Géro Stephan D. , Vuilhorgne Marc
Published: December 2004

The synthesis of a large variety of enantiomerically pure substituted reactive cyclopentenes 16, 23, 24 and 28 have been synthesized from the readily available (−)‐quinic acid 1. The straightforward strategy involves a high‐yielding intramolecular aldolization‐dehydration of acyclic 1,6‐dialdehydes 13, 18, 19 and 27 obtained by oxidative cleavage of cyclohexanediols 5, 7, 11 and 12, using either lead tetraacetate or triphenylbismuth carbonate. Neither sulfoxide formation nor racemization of the intermediate dialdehydes at the oxygenated chiral centre was observed. Transformation of the thioacetal 25 to the corresponding ketone 26 using phenylselenic anhydride is also described.
Saponins with Molluscicidal Properties from Lonicera nigraL
Authors: Domon Bruno , Hostettmann Kurt
Published: December 2004

Eight triterpenoid saponins (1–8) have been isolated from the berries of Lonicera nigra L. (Caprifoliaceae) by combination of droplet counter‐current chromatography and column chromatography on silica. The structures have been established by 1H‐NMR., 13C‐NMR. spectroscopy, FD.‐MS., FAB.‐MS. and D./CI.‐MS., and on the basis of acidic and basic hydrolyses. The monodesmosidic saponins 1–5 possess strong molluscicidal activity against the schistosomiasis‐transmitting snail Biomphalaria glabrata, whereas the bidesmosidic saponins 6–8 are inactive.
Spirocoleone: Synthese und Charakterisierung von vier diastereomeren Spiro (methylcyclopropan)‐Substrukturen; Revision der Konfiguration an C(12) und C(15) von Coleon P und Derivaten sowie von Coleon‐Z‐Derivaten; Röntgenstrukturanalysen von Lanugon J und weiteren Spirocoleonen
Authors: Rüedi Peter , Schmid Jean Martin , Prewo Roland , Bieri Jost Hans , Eugster Conrad Hans
Published: December 2004

Spirocoleons: Synthesis and Characterization of Four Diastereomeric Spiro (methylcyclopropane) Substructures; Revision of the Configuration at C(12) and C(15) of Coleon P and Derivatives and Coleon‐Z Derivatives; X‐Ray Analysis of Lanugon J and of Further Spirocoleons

X‐ray analyses show the correctness of the previously published structure of coleon Q (1), establish the structure of lanugon J (4a), and necessitate a revision of the configuration at C(12) and C(15) in coleon P (3a) and its derivatives 3b and 3c, and furthermore of the coleon Z derivatives 11a–11d. Two further diastereomeric spiro (methylcyclopropane) substructures have been generated by photoisomerization of lanugon J (4a) and 12‐O‐desacetylcoleon N (8); they represent the novel cis‐type B with (12R, 13R, 15S)‐ and the novel trans‐type D with (12R, 13R, 15R)‐configuration (Scheme 1). The structures of the photoproducts 5a ((12R, 13R, 15R)‐lanugon J) and 7a ((12R, 13R, 15S)‐lanugon J) were established by X‐ray analysis. So far, only two of the eight possible diastereomers of the spiro‐(methylcyclopropane) substructure I have been detected in nature, i.e. the trans‐type A with (12R, 13S, 15S)‐ and the cis‐type C with (12R, 13S, 15R)‐configuration. The four diastereomers A‐D, all possessing (12R)‐configuration, show very similar properties. However, careful comparison of spectral and chiroptical data allow a differentiation, even in the case of functionalization of H3C(17). The (12S)‐counter‐parts could not yet be prepared.