bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphoramidites of Chiral (Rp)‐and (Sp)‐Configurated d(T[P‐18O]‐A): Synthesis, Configurational Assignment, and Use as Dimer Blocks in Oligonucleotide Synthesis
Authors: Herdering Wilhelm , Kehne Andreas , Seela Frank
Published: December 2004

The N,N‐diisopropylphosphoramidites 10a and 10b of appropriately protected chiral diastereoisomers of d(T[P‐18O]‐A) (8a and 8b, resp.), chiral by virtue of the isotope 18O at the P‐atom, have been synthesized. The 18O‐isotope was incorporated by oxidation of the phosphite triester 3 with H2[18O]/I2. Separation of the diastereoisomers was accomplished by flash chromatography of the O‐3′‐deprotected phosphate triesters 5a/b. The absolute configuration at the chiral P‐atom was deduced from the methylation products of the fully deprotected diastereoisomers 8a and 8b. Phosphinylation of 5a and 5b yielded the configurationally pure phosphoramidites 10a and 10b, respectively, which were then employed in solid‐phase synthesis to yield the self‐complementary oligomers d(G‐A‐G‐T‐(Rp)‐[P‐18O]‐A‐C‐T‐C) (13) and d(G‐A‐G‐T‐(SP)‐[P‐18O]‐A‐C‐T‐C) (14), respectively.
Polar Effects. Part 14. Inductive Charge Dispersal in Bicyclo[2.2.2]oct‐1‐yl Cations
Authors: Bielmann Rolf , Grob Cyril A. , Küry Dieter , Yao Guo Wei
Published: December 2004

The rate constants (log k) for solvolysis of 2‐, 3‐, and 4‐substituted bicyclo[2.2.2]octyl p‐nitrobenzenesulfonates 10, 11 and 12, respectively, correlate linearly with the corresponding inductive substituent constants s̀. The formation of the ion pairs 9 is, therefore, controlled by the I effect of neighboring substituents. It follows from the corresponding reaction constants ρ1 of −1.54, −1.12, and −1.22 that inductivity is highest at the positions α to C(1). It is lower and practically equal at the β‐ and γ‐positions. Therefore, charge dispersal is similar to that previously observed in the quinuclidinium ion 7.
Cyclisation of 7‐Deazaxanthine‐9‐propionic Acid to an Active‐Site‐Directed, Irreversibly Acting Inhibitor of Xanthine Oxidase
Authors: Rosemeyer Helmut , Kretschmer Uwe , Seela Frank
Published: December 2004

Phase‐transfer alkylation of 2,4‐dimethoxy‐7H‐pyrrolo[2,3‐d]pyrimidine (2) with ethyl 3‐bromopropionate leads regioselectively to ethyl 2,3‐dimethoxy‐7H‐pyrrolo[2,3‐d]pyrimidine‐7‐propionate (3a). After saponification and ether cleavage, the functionalised 7‐deazaxanthine 4b was obtained. Reaction of 4b with H2O‐soluble carbodiimide resulted in an intramolecular acylation at N(3) with formation of the tricyclic compound 5. Compound 5 ‐ bearing a reactive lactam ring ‐ is an active‐site‐directed, irreversibly acting inhibitor of xanthine oxidase from cow's milk.
The Structure Elucidation of Pseudothiocolchicine
Authors: Danieli Bruno , Lesma Giordano , Palmisano Giovanni , Riva Renata
Published: December 2004

A colchicine derivative, previously isolated from the reaction of isocolchicine with sodium thiomethoxide in aqueous MeOH, was now identified as 11‐(methylthio)isocolchicine on the basis of 1H‐, 13C‐NMR spectra and chemical correlation. This reaction represents the first example of abnormal nucleophilic displacement (telesubstitution) in the colchicine chemistry.
Synthesis of Alkenyl‐Substituted Allenecarboxylates
Authors: Lang Robert Werner , Kohl‐Mines Elisabeth , Hansen Hans‐Jürgen
Published: December 2004

The Wittig olefination of decanoyl chloride by using the phosphonium salt 1 in the presence of two equivalents of Et3N represents a one‐step synthesis of the racemic form of the naturally occurring pheromone (–)‐2 which contains an alkenyl‐substituted allenic moiety (ef. Scheme 1). It is also shown, that unsaturated acyl chlorides which contain at least one γ‐H‐atom undergo the Wittig reaction with an appropriate phosphorane yielding γ‐alkenyl‐substituted α‐allenic esters and α‐allenic γ‐lactones, respectively (ef. Schemes 2 and 3).
Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Absolute Konfiguration
Authors: Fässler Alexander , Kobelt André , Pfaltz Andreas , Eschenmoser Albert , Bladon Christine , Battersby Alan R. , Thauer R. K.
Published: December 2004

Factor F430 from Methanogenic Bacteria: Absolute Configuration

Experiments on F430M (2) aiming at a potentially biomimetic, reductive reconstruction of the F430 (1) chromophore from corresponding pyrrocorphinate intermediates provided us with F430 derivatives which contain an isobacteriochlorinate chromophore system similar to the one occurring in sirohydrochlorin (3) (cf. the Scheme). Comparison of their CD spectra with the‐CD spectrum of nickel(II)‐sirohydrochlorinate octamethyl ester demonstrates that the absolute configurations of factor F430 and sirohydrochlorin in the region of rings A and B are the same.
Chemical Alterations in Native Histone Octamer Complexes Induced by the Attak of · OH and · N3 Radicals
Authors: Deeg Klaus‐Jürgen , Katsikas Lynne , Schnabel Wolfrman
Published: December 2004

·OH Radicals generated by short electron‐beam pulses were allowed to attack histone octamer complexes (extracted from calf‐thymus chromatin) in N2O‐saturated dilute solution (0.5–1.3 g/l, [NaClO4] = 1 – 2M, pH 9). They induced a volume contraction due to intra‐complex cross‐linking. In this process, essentially non‐tyrosine moieties of the proteins were involved. Phenol coupling via tyrosyl radicals occurred mainly as an intramolecular reaction, i.e., it was restricted to single histone moelecules. Furthermore, it turned out that only about 55% of the tyrosine moieties were accessible to attacking ·OH and/or ·N3 radicals. When ·N3 radicals were generated via continuous irradiation of N2O‐saturated octamer solutions containing NaN3 with 60Co‐γ‐rays, dimers, trimers, and tetramers were detected by SDS gel electrophoresis, in contrast to pulse radiolysis where only dimers were found. These results were explained in terms of denaturation being induced by small chemical changes and causing partial or complete dissociation of the complexes thus permitting, in the course of the γ‐irradiation, the attack and conversion of amino‐acid moieties non‐accessible in the native octamer complexes. Removal of steric restrictions for the combination of tyrosyl radicals may also play a role. By time‐resolved absorption measurements, it was shown that, upon the attack of intact octamer complexes by ·OH radicals, tyrosyl radicals were formed which were converted to dityrosine groups according to two modes with half‐lives of several 100 m̈s and 1–2 ms, respectively. Cross‐linking of histone molecules occurred with a definitely lower rate (1st half‐life: 50 100 ms). This process was detectable both by optical absorption measurements at λ = 300 400 nm and by light‐scattering measurements.
Interactions between Functional Groups. Part III. The Structure of N,N‐Dimethyl‐8‐nitro‐1‐naphthaleneamine in Seven Crystalline Environments
Authors: Egli Martin , Wallis John D. , Dunitz Jack D.
Published: December 2004

The N,N‐dimethyl‐8‐nitro‐1‐naphthaleneamine molecule has been observed in seven environments in three crystal modifications. A range of conformations, related by conrotatory motions about the two exocyclic CN bonds, is observed. In all seven conformations, the lone pair of the amino N‐atom is directed approximately towards the nitro N‐atom, which is slightly pyramidalized towards the amino group. The NO2 group appears to be a poorer through‐space electron acceptor than the carboxylic ester group, in contrast to their through‐bond electron‐accepting properties.
Structural and Spectroscopic Investigations of the 1:1 Complex between Europium Nitrate and a Tetraoxadiaza Macrocycle
Authors: Bünzli Jean‐Claude G. , Leonard Gordon A. , Plancherel Dominique , Chapuis Gervais
Published: December 2004

The crystal and molecular structure of dinitrato(1,7,10,16‐tetraoxa‐4,13‐diazacyclooctadecane)europium(III) nitrate, ([Eu(NO3)2(C12H26N2O4)]NO3) has been determined from single‐crystal X‐ ray diffraction: a = 12.567(3), b = 11.585(3), c = 16.354(5) Å, β = 112.45(2)°, space group P21/n, Z = 4. The structure consists of discrete dinitrato complex cations and of nitrate anions. The Eu(III) ion is 10‐coordinate, bonding to the six donor atoms of the macrocycle and to four O‐atoms of the two bidentate nitrates. The mean distances are EuO(ether) = 2.60(2), EuO(NO3) = 2.47(3) and EuN = 2.62(2) Å. The metal site has an approximate C2 symmetry. The IR and Raman spectra show the presence of an ionic and of two bonded bidentate nitrates. These latter have a different v1‐v4 splitting, which reflects their dissymmetrical bonding. Luminescence spectra have been recorded at 296, 77, and 4 K by laser‐excitation techniques. One sharp 5D0←7F0 transition was observed and almost all the sublevels of the 7FJ manifold could be identified. The interaction between a sharp distribution of the phonon states (especially between 950 and 1200 cm−1) and the electronic 7F2 sublevels results in the presence of several satellite lines accompanying the 5D0→7F2 transition. In MeCN solutions, both luminescence and conductivity data point to the presence of the [Eu(NO3)2(2,2)]+ cation.
Reaktionen von 3‐substituiertem 5‐Trifluormethyl‐1,3,4‐oxadiazol‐2(3H)‐on mit Nucleophilen
Authors: Kristinsson Haukur , Winkler Tammo , Mollenkopf Max
Published: December 2004

Reactions of 3‐Substituted 5‐Trifluoromethyl‐1,3,4‐oxadiazol‐2(3H)‐one with Nucleophiles

The 3‐substituted 5‐trifluoromethyl‐1,3,4‐oxadiazolones 3, 4, 13, and 15 are attacked by N‐ and S‐nucleophiles either at the ring C‐atom C(2) or C(5). Depending on the nature of the substituent and the nucleophile, the ring‐opening products 7, 10, 12, and 14 or the ring‐enlargement products 16 are formed. The reaction of 4 with thiols is a novel variant of the Grob‐type fragmentation. The reactivity of the 1,3,4‐oxadiazolones is compared with that of the analogous 1,3,4‐thiadiazolones. The structures of the new compounds were elucidated by 1H‐ and 13C‐NMR spectroscopy.
Optisch aktive 4,5‐Epoxy‐4,5‐dihydro‐α‐ionone und Synthese der stereoisomeren 4,5:4′,5′‐Diepoxy‐4,5,4′,5′‐tetrahydro‐ϵ,ϵ‐carotine und der sterische Verlauf ihrer Hydrolyse
Authors: Uebelhart Peter , Baumeler Andreas , Haag Andreas , Prewo Roland , Bieri Jost Hans , Eugster Conrad Hans
Published: December 2004

Optically Active 4,5‐Epoxy‐4,5‐dihydro‐α‐ionones; Synthesis of the Stereoisomeric 4,5:4′,5′‐Diepoxy‐4,5,4′,5′‐tetrahydro‐ϵ,ϵ‐carotenes and the Steric Course of their Hydrolysis

We prove that epoxidation with peracid of α‐ionone, contrary to a recently published statement, predominantly leads to the cis‐epoxide. Acid hydrolysis affords a single 4,5‐glycol whose structure, established by an X‐ray analysis, shows that oxirane opening occurred with inversion at the least substituted position (C(4)). Stable cis‐and trans‐epoxides are prepared by epoxidation of the C15‐phosphonates derived from α‐ionone. Both the racemic and optically active form are used for the synthesis of the 4,5:4′,5′‐diepoxy‐4,5,4′,5′‐tetrahydro‐ϵ,ϵ‐carotenes having the following configuration in the end groups: meso‐cis/cis, meso‐trans/trans, rac‐cis/trans, rac‐ and (6R, 6′ R)‐cis/cis, rac‐ and (6R, 6′R)‐trans/trans, rac‐ and (6R, 6′R)‐cis/trans, and (6R, 6′ R)‐cis/ϵ. Acid hydrolysis of the cis/cis‐epoxycarotenoids under relatively strong conditions occurs again with inversion at C(4)/C(4′) in case of the cis/cis‐epoxycarotenoids, but at C(5)/C(5′) in case of the trans/trans‐epoxycarotenoids. An independent synthesis of this 4,5,4′,5′‐tetrahydro‐ϵ,ϵ‐carotene‐4,5,4′,5′‐tetrol is presented. The irregular results of the oxirane hydrolysis are explained by assumption of neighbouring effects of the lateral chain. 400‐Mz‐1H‐NMR data are given for each of the stereoisomeric sets. In the visible range of the CD spectra, the (6R, 6R′)‐epoxycarotenoids compared with (6R, 6R′)‐ϵ,ϵ‐carotene exhibit an inversion of the Cotton effects.
An Ag‐Atom in the 6‐6 Subunit of a Zeolite: Model Calculations
Authors: Calzaferri Gion , Forss Lars
Published: December 2004

Self‐sensitisation of photo‐oxygen evolution occurs in aqueous dispersions of silver zeolites. In presence of Cl−, chlorine is the photoproduct in acidic medium, and the same type of self‐sensitisation occurs. Self‐sensitisation means that systems which are first insensitive to light of a certain wavelength become photo‐active after they have been illuminated by light of higher energy. For a better understanding of silver zeolites, we have carried out EH‐MO calculations on the 6–6 subunit (SBU) of a zeolite, on the 6–6 SBU with an Ag‐atom in the center, on the 6–6 SBU with one Ag‐atom in the center and one outside on top of the hexagon, and finally on another with one Ag‐atom in the center and two Ag‐atoms outside, each on top of a hexagon. The Ag0 in the cage of the 6–6 SBU is significantly polarized by the 6–6 SBU environment. The energy barrier to escape the 6–6 SBU is 0.8 eV for Ag0 and 0.5 eV for Ag+. The HOMO of the Ag(6–6 SBU) is a totally symmetric 5s* orbital and the LUMO is a 5pz* type. 5pz*←5s* electronic excitation reduces the energy barrier and allows an (Ag0)* to exit the 6–6 SBU, provided the excited‐state lifetime is long enough. The MO picture predicts low‐energy charge‐transfer transitions from the zeolite framework to the 5s* orbital. The highest occupied orbitals of the zeolite framework are localized on the O‐atoms. Interactions between an Ag‐atom in the 6–6 SBU and one or two external Ag‐atoms are discussed.
Fluorine‐Containing Organozinc Reagents Part 1 A Simple Synthesis of 2,2‐Dichloro‐3,3,3‐trifluoropropanol
Authors: Lang Robert Werner
Published: December 2004

The title compound 1, which can be regarded as a synthetic equivalent of substituted 1,1,1‐trifluoroacetone 2, is prepared by Zn‐induced reductive addition of 1,1,1‐trichloro‐2,2,2‐trifluoroethane (3) to formaldehyde (4). A brief survey of the scope of this CC‐bond formation leading to a variety of new CF3‐containing synthetic building blocks is also given.
5‐(N‐Arylnortropan‐3‐yl)‐ and 5‐(N‐Arylpiperidin‐4‐yl)‐2,4‐diaminopyrimidines. Novel Inhibitors of Dihydrofolate Reductase
Authors: Maag Hans , Locher Rita , Daly John J. , Kompis Ivan
Published: December 2004

Based on a computer‐assisted analysis of the three‐dimensional structure of the binary complex of E.coli dihydrofolate reductase (DHFR) with methotrexate, 5‐(N‐arylnortropan‐3‐yl)‐ and 5‐(N‐arylpiperidin‐4‐yl)‐2,4‐diaminopyrimidines 2 and 4 were designed as inhibitors of DHFR. Syntheses of the designed compounds have been carried out. The most potent compound 2a inhibited E. coli DHFR with Ki = 0.49.10−9M. The activities within the series of compounds synthesized could be rationalized by molecular‐modelling experiments which served as the basis of this work. Several compounds within the presented series exhibit antimalarial activities in vitro and in vivo.
Nucleosides and nucleotides part 24 Investigation of ribo‐ and deoxyribonucleosides and ‐nucleotides by fast‐ atom‐bombardment mass spectrometry
Authors: Hogg Alan M. , Kelland Janice G. , Vederas John C. , Tamm Christoph
Published: December 2004

The fast‐atom‐bombardment mass spectra (FAB‐MS) of a series of ribo‐ and deoxyribonucleosides and ‐nucleotides were examined in both positive‐ion and negative‐ion modes. Behaviour of cytosine analogs having unnatural bases (2(1H)‐pyrimidone, 2(1H)‐pyridinone, and 4‐amino‐2(1H)‐pyridinone) was similar to that of compounds having naturally occurring bases. Nucleotides protected by dimethoxytrityl and p‐chlorophenyl groups were also investigated using this technique. Use of negative‐ion mode reduces interference from positive counter‐ions (e.g., Na+) and allows rapid sequence determination of simple di‐ and trinucleotides.
Synthese und Strukturaufklärung von Merucathin und Pseudomerucathin. Zwei Inhaltstoffe von Catha edulis FORSK
Authors: Wolf Jean‐Pierre , Pfander Hanspeter
Published: December 2004

Synthesis and Structure Elucidation of Merucathine and Pseudomerucathine. Two Constituents of Catha edulis FORSK.

Starting from L‐alanine, two constituents of Catha edulis FORSK. (3R,4S)‐4‐amino‐1‐phenyl‐1‐penten‐3‐ol ((3R,4S)‐4, merucathine) and (3S,4S)‐4‐amino‐1‐phenyl‐1‐penten‐3‐ol ((3S,4S)‐4, pseudomerucathine) were synthesized.
PE Spectra of Dewar Benzenes, Bridged by a Cyclohexadiene or a Butadiene Unit
Authors: Gleiter Rolf , Krennrich Gerhard , Bischof Peter , Tsuji Takashi , Nishida Shinya
Published: December 2004

The electronic structure of [4.2.2]propella‐2,4,7,9‐tetraene (1), 2,5‐etheno[4.2.2]propella‐3,7,9‐triene (2), and of several hydrogenated derivatives of 2 has been investigated using He(I) PE spectroscopy and MO calculations. It is found that in 2 the 1,4‐cyclohexadiene moiety interacts considerably with the bicyclo[2.2.0]hexadiene unit, while in 1 the interaction between the butadiene fragment and the Dewar benzene unit is minute. The syntheses of 3–5 are reported.
Neue Diterpene aus Blattdrüsen von Plectranthus barbatus (Labiatae). Die absolute Konfiguration der 2‐Hydroxypropyl‐Seitenkette in Coleon E
Authors: Rüedi Peter
Published: December 2004

Novel Diterpenoids from Leaf Glands of Plectranthus barbatus (Labiatae). The Absolute Configuration of the 2‐Hydroxypropyl Group in Coleon E

In addition to the previously reported quinone methides coleon E (1a), coleon F (2a) and the spirocoleon 9 (plectrin), novel rearranged abietanoid dienediones, called (16R)‐plectrinon A (3a) and plectrinon B (5) as well as the allylroyleanone 8a have been isolated from Plectranthus barbatus and their structures elucidated mainly by spectroscopy. Closer investigation of acetylations of 1a and 2a established the hitherto unknown structures 1c, 2c, 3b, 10a, 10b, 11a, 11b, 12a, and 12b. The derivatives 3b, 11a, 11b, 12a, and 12a, and 12b are the products of a nucleophilic attack at the quinone methide system. The analysis of the 13C‐NMR spectra led to the full assignment of the signals in 1a, 1b, 2a, 3a, and 8a. Correlations by partial syntheses of 3a, from coleon E(1a), after oxidation or acetylation/saponification of the latter, established the (R)‐configuration of the 2‐hydroxypropyl group in 1a. The biomimetic transformation of plectrin (9) into (16R)‐coleon E (1a) is shown to proceed via the unexpected, highly reactive 2‐methylspiro[cyclopropane‐1,2′‐(2′H)‐phenanthrene]‐1′,3′, 6′‐trione 13. The solvolysis of the spiro(methylcyclopropane) moiety takes place with inversion of the configuration at the attacked C‐atom, as established in a previous communication. The 1,3,6‐trione 13 is supposed to be also the key intermediate in the biosynthesis of the allyl group in coleon F (2a) which proceeds via a homosigmatropic [1,5]‐H shift.
Photogeneration of Carbon Monoxide and of Hydrogen via Simultaneous Photochemical Reduction of Carbon Dioxide and Water by Visible‐Light Irradiation of Organic Solutions Containing Tris(2,2′‐bipyridine)ruthenium(II) and Cobalt(II) Species as Homogeneous Catalysts
Authors: Ziessel Raymond , Hawecker Jeannot , Lehn Jean‐Marie
Published: December 2004

CO and H2 are photogenerated simultaneously by visible‐light irradiation of systems containing a photosensitizer, the [Ru(bpy)3]2+ complex, Co(II) species as homogeneous catalysts, which mediate CO2 and H2O reduction by intermediate formation of Co(I), a tertiary amine as electron donor, which provides the electrons for the reduction, and an organic solvent which also facilitates dissolution of CO2. The efficiency of (CO + H2) gas production and the selectivity CO/H2 markedly depend upon the composition of the medium, the nature of the tertiary amine, the solvent, and the ligand of the Co ions. 2,9‐Dimethyl‐1,10‐phenanthroline is particularly effective in promoting CO and H2 formation, giving a quantum yield of 7.7% in (CO + H2) (1.2% for CO and 6.5% for H2). The process consists of two catalytic cycles: a photocatalytic cycle for the Ru complex and a double dark reaction pathway for the Co species; oxidative and/or reductive quenching of the excited state of the photosensitizer lead to the formation of Co(I) species which reduce either CO2 or H2O to CO or H2, respectively.
Isoswerosid, ein neues Secoiridoidglycosid aus den Wurzeln des Zwergholunders Sambucus ebulus L. (Caprifoliaceae). 2. Mitteilung über die Inhaltsstoffe der Zwergholunderwurzel
Authors: Gross Gian‐Andrea , Sticher Otto
Published: December 2004

Isosweroside, a New Secoiridoid Glycoside from the Roots of Sambucus ebulus L. (Caprifoliaceae)

The paper describes the isolation and structure elucidation of isosweroside (6‐(β‐D‐ glucopyranosyloxy)‐methyl‐9‐vinyl‐2,8‐dioxabicyclo[3.3.1]non‐6‐en‐3‐one), the first Valeriana‐type secoiridoid glycoside from the roots of Sambucus ebulus L. along with the two known glycosides ebuloside and morroniside.
Diels‐Alder Approach to Highly Functionalized Tertiary α‐Hydroxy Ketones: A Novel Route to the Hexahydrobenzofuran Portion of the Avermectins and Milbemycins
Authors: Ireland Robert E. , Obrecht Daniel M.
Published: December 2004

A highly regio‐ and stereoselective Diels‐Alder reaction between dienophiles of type I and dienes of type II (Scheme 1) gives rise to Diels‐Alder adducts of type III. Upon treatment with BF3.Et2O, these adducts are smoothly converted into the corresponding enones (Scheme 6). Under mild acidic conditions, enone (±)‐33 gave bicyclic diketone (±)‐34 via an intramolecular Michael‐type addition. Diketone (±)‐34 has the correct relative configuration and a suitable ketone function at C(6) for further conversion into the hexahydrobenzofuran portion of the avermectins and milbemycins.
Photochemical reactions. 148th communication. Photochemistry of acylsilanes: Preparation, photolyses, and thermolyses of α,β‐unsaturated silyl ketones
Authors: Scheller Markus E. , Iwasaki Genji , Frei Bruno
Published: December 2004

The syntheses, photolyses, and thermolyses of the α,β‐unsaturated silyl ketones (E/Z)‐7, (E)‐8, and (E)‐9 are described. On n,π*‐excitation (λ > 347 mm), the aforementioned compounds undergo (E/Z)‐isomerization followed by γ‐H abstraction. The intermediate enols are trapped intermolecularly by siloxycarbenes leading to the dimeric acetals 27A + B, 30A + B, and 31A + B. In addition, the acylsilanes (E/Z)‐7 undergo photoisomerization by δ‐H abstraction furnishing the acylsilanes 29A + B. Flash vacuum thermolyses (FVT) of (E/Z)‐7, (E/Z)‐8, and (E)‐9 give rise to intramolecular reactions of the siloxycarbene intermediates. Thus, FVT (520°) of (E)‐ and (Z)‐7 selectively leads to the enol silyl ethers 32 and (E)‐33, respectively, arising from carbene insertion into an allylic C–‐H bond. FVT of (E/Z)‐8 (560°) and (E)‐9 (600°) affords the trienol silyl ethers 34A + B and the cyclic silyl ethers 37A + B, respectively, which are formed by CH insertion of the siloxycarbenes. As further products of (E)‐8 and (E)‐9, the bicyclic enol ethers 35 and 36 are formed, presumably via siloxycarbene addition to the cyclohexene CC bond.
Neue Diterpenoide aus Blattdrüsen einer Plectranthus sp. aus Rwanda
Authors: Alder Alfredo Carlos , Rüedi Peter , Prewo Roland , Bieri Jost H. , Eugster Conrad Hans
Published: December 2004

Novel Diterpenoids from Leaf‐Glands of a Plectranthus sp. from Rwanda

More than 20 highly modified abietanoid compounds belonging to 6,7‐dioxocoleons, serveral kinds of royleanones, spirocoleons, extended quinones, quinone methides, and 1,4‐phenanthraquinones have been isolated from a Plectranthus sp. from the borders of Lake Kiwu (Rwanda). The structure of plectranthon A (1), a 5,7,8‐trimethyl‐1,4‐phenanthraquinone, has been confirmed by an X‐ray analysis of its p‐bromobenzoate. It is twisted around the C(4)–C(5) moiety; this fact renders the molecule chiral. Notable features of the hydroxylation pattern in all of the isolated compounds are: (a) a predominant hydroxylation at C(16) (abietan numbering) leading to the (15S)‐configuration of the 2‐hydroxy‐l‐methylethyl side‐chain and to the (13S, 15R)‐configuration of the derived spirocyclopropanes and to the derived (S)‐2‐hydroxypropyl side‐chain; (b) the 6β,7α‐dihydroxylation which, together with further hydroxylations at C(3) and/or C(2), are considered as a prerequisite for the formation of the conjugated system extending over rings A, B and C (e.g. in the coleons E and F), hence allowing a complete aromatization of the basic ring skeleton. The reasons for these extensive dehydrogenation and oxygenation reactions that cost the plant a great many of oxidation equivalents are not clear. Presumably, these modifying reactions preceed the degradation of the ring system.
X‐Ray Crystallographic and MO Studies on the Conformation of Corynoline and the Related Compounds
Authors: Kamigauchi Miyoko , Noda Yuko , Takao Narao , Ishida Toshimasa , Inoue Masatoshi
Published: December 2004

The crystal structure of (±)‐corynoline (1) has been determined by X‐ray diffraction methods. The rings B and C form the half‐chair and the twist‐half‐chair conformations, respectively. The B/C ring conjunction exists in an anti‐cis conformation, with a N …︁ HO intramolecular H‐bond. Conformational energy calculation by the CNDO/2 method show that the conformations of 1, (+)‐chelidonine (2), and their acetates, observed in crystal structures, are all in the one of total energy minimum.
Anion Selectivities of Triorganyltin Acetates and Halides in Solvent Polymeric Membranes
Authors: Wuthier Urs , Pham Hung‐Viêt , Rusterholz Bruno , Simon Wilhelm
Published: December 2004

A series of triorganyltin compounds of the type R3SnY and RR2SnY has been studied in view of their anion selectivities exhibited in solvent polymeric membranes. A large variety of selectivity patterns has been observed first by varying the concentration of a given ionophore in the membrane phase, and second by using ionophores which differ in the organic substituents R on the Sn centre. With more space consuming substituents R, the observed selectivity patterns become more and more similar to that of a blank membrane, suggesting steric hindrance for the pentacoordination of the corresponding ionophores by sample anions.
Struktur von Edulon A
Authors: Künzle Josef Max , Rüedi Peter , Prewo Roland , Eugster Conrad Hans
Published: December 2004

Structure of Edulon A

Based on new chemical reactions and an X‐ray analysis of the derived camphanic ester 2e, edulon A has been shown to have the structure 2a, i.e. (10bS, 1′S)‐8‐(2′‐acetoxy‐1′‐methylethyl)‐2,4,6, 10b‐tetrahydro‐7,9, 10‐trihydroxy‐3, 10b‐dimethyl‐1H‐5‐oxaaceanthrylene‐4,6‐dione. Therefore, it is not a 2H‐1‐oxapyrene as previously assumed, but a derivative of the novel 4H‐5‐oxaaceanthrylene skeleton.
(Cyclophan‐Metall)‐Komplexe: Synthese und Kristallstruktur von ([3.3]Paracyclophan)gallium(I)‐tetrabromgallat(III)
Authors: Schmidbaur Hubert , Bublak Wolfgang , Huber Brigitte , Müller Gerhard
Published: December 2004

Cyclophane‐Metal Complexes: Synthesis and Crystal Structure of ([3.3]Paracyclophane)gallium(I) Tetrabromogallate(III)

[3.3]Paracyclophane forms 1:1 complexes 2a and 2b with both Ga[GaCl4] and Ga[GaBr4]. The crystalline products obtained from toluene solution at room temperature are much less sensitive to air and moisture than most other arene complexes of Ga(I). Solubilities in standard organic solvents are very low, suggesting coordination polymers. The X‐ray diffraction analysis of 2b confirms the presence of a two‐dimensional network. Both aromatic rings of each cyclophane molecule are η6‐coordinated from the outer side to Ga(I)‐atoms. The position of these metal cations is 2.75 Å above the ring centres. The arene rings are parallel within each cyclophane, but tilted by 48.5° with respect to those of the neighbouring cyclophane. The coordination sphere of the Ga(I) centres is completed by two Br‐atoms of two GaBr anions, which link the Ga(I) cations to give … Ga[GaBr4] Ga[GaBr4]Ga … strands. The double interconnection of the Ga(I)‐atoms gives rise to a two‐dimensional sheet structure, which is thus different from the structure of the previously described Ga[GaBr4] complex of [2.2]paracyclophane, where a three‐dimensional network was observed.
The Formation of Bridged Bicyclic 1,2,4‐Trioxanes by Intramolecular Capture of β‐Hydroperoxy Cations
Authors: Jefford Charles W. , Favarger France , Ferro Serenella , Chambaz Daniel , Bringhen Alain , Bernardinelli Gerald , Boukouvalas John
Published: December 2004

The 1,4‐endoperoxide, prepared from 3‐(4‐methylnaphth‐1‐yl)propanal by photo‐oxygenation in CH2Cl2, gave on treatment with Amberlyst‐15®, 3,10b‐epidioxy‐2,3,4a,10b‐tetrahydro‐6‐methyl‐1H‐naphtho[2,1‐b] pyran in 85% yield. Its structure was determined by X‐ray crystal structure analysis. The 1,2,4‐trioxane moiety is locked in a twist‐boat conformation with trans fusion to the parent six‐membered ring. The 1,4‐endoperoxides of the methyl, butyl, and phenyl ketone analogues of the aforementioned aldehyde underwent similar acid‐catalyzed rearrangement to the corresponding bridged bicyclic trioxanes in 94, 47, and 48% yields, respectively.
Enantioselective Synthesis of β‐Necrodol and of 1‐Epi‐β‐necrodol via Asymmetric 1,4‐Addition and Magnesium‐Ene Cyclization. Preliminary Communication
Authors: Oppolzer Wolfgang , Schneider Philippe
Published: December 2004

Enantiomerically pure β‐necrodol (1) and its 1‐epimer 16 have been synthesized starting from aldehyde 5. The two key steps are an asymmetric conjugate addtion/Mannich reaction tandem (10→12) and a type‐II‐magnesiumene cyclization/oxidation sequence (14→1 + 16).
Conformationally Restricted Analogs of Platelet‐Activating Factor (PAF)
Authors: Hadváry Paul , Weller Thomas
Published: December 2004

The synthesis of the five‐membered cyclic phosphorodiamidic‐acid derivatives 10 and 11 as well as the preparation of the six‐membered cyclic phosphates 18, 19, 22–25, and phosphoramidates 27–32 is described. The effects of these conformationally restricted platelet‐activating factor analogs on rabbit platelet aggregation are briefly discussed. The 2‐oxo‐1,3,2‐dioxaphosphorinanes 19, 25, and 30 were found to be equally potent platelet‐activating factor antagonists as the known thiazolium salt 33.
4‐Methylumbelliferyl 5‐Acetamido‐3,4,5‐trideoxy‐α‐D‐manno‐2‐nonulopyranosidonic Acid: Synthesis and Resistance to Bacterial Sialidases
Authors: Baumberger Franz , Vasella Andrea , Schauer Roland
Published: December 2004

The synthesis of 4‐methylumbelliferyl α‐D‐glycoside 13 of N‐acetyl‐4‐deoxyneuraminic acid and its behaviour towards bacterial sialidases is described. N‐Acetyl‐4‐deoxyneuraminic acid (1) was transformed into its methyl ester 2 and then acetylated to give the anomeric pentaacetates 3 and 4 of methyl 4‐deoxyneuraminate and the enolacetate 5 (Scheme). A mixture 3/4 was treated with HCl/AcCl to give the glycosyl chloride, which was directly converted into the 4‐methylumbelliferyl α‐D‐glycoside 9 of methyl 7‐O,8‐O,9‐O,N‐tetraacetylneuraminate and into the 2,3‐dehydrosialic acid 11. The ketoside 9 was de‐O‐acetylated to 12 with NaOMe in MeOH. Saponification (NaOH) of the methyl ester 12 followed by acidification gave the free 13, which was also converted into the sodium salt 14 by passage through Dowex 50 (Na+). The 4‐deoxy α‐D‐glycoside 13 is not hydrolyzed at significant rates by Vibrio cholerae and Arthrobacter ureafaciens sialidase. Neither the free N‐acetyl‐4‐deoxyneuraminic acid (1), nor the α‐D‐glycoside 13 inhibit the activity of these sialidases.
Nucleosides and nucleotides. Part 25.. Synthesis of a protected 1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐1 H‐benzimidazole 3′‐phosphate
Authors: Papageorgiou Christos , Tamm Christoph
Published: December 2004

1‐(2′‐Deoxy‐5′‐O‐dimethoxytrityl‐′‐D‐ribofuranosyl)‐1 H‐benzimidazole 3′‐[(p‐chlorophenyl)(2‐cyanoethyl) phosphate] (6) has been synthesized from 1‐(β‐D‐ribofuranosyl)‐1H‐benzimidazole (3b) using regiospecific 2′‐deoxygenation. The latter compound was obtained by glycosylation of benzimidazole with the D‐ribose derivative 2 leading exclusively of the β‐D‐anomer.
A Simple and Effective Chemical Phosphorylation Procedure for Biomolecules
Authors: Bannwarth Willi , Trzeciak Arnold
Published: December 2004

A general chemical phosphorylation method based on P(III) chemistry has been developed. The system is demonstrated for the phosphorylation of oligonucleotides, directly after their synthesis on a solid support, and for the O‐phosphorylation of serine, threonine, and tyrosine as well as for a serine‐containing peptide.
Syntheses of Tetrahydrolipstatin and Absolute Configuration of Tetrahydrolipstatin and Lipstatin
Authors: Barbier Pierre , Schneider Fernand
Published: December 2004

Lipstatin (1), a natural product, and tetrahydrolipstatin (2) are pancreatic lipase inhibitors. Non‐stereoselective and partially stereoselective syntheses of 2 are used to establish the absolute configuration of tetrahydrolipstatin and lipstatin.
Photoionization of Naphthalene and Anthracene in Acetonitrile
Authors: Vauthey Eric , Haselbach Edwin , Suppan Paul
Published: December 2004

Naphthalene and anthracene undergo a monophotonic ionization process in MeCN to produce the radical cations in low quantum yields (around 0.06 for anthracene). This reaction originates from the relaxed singlet excited state S1, and it is not due to traces of H2O in the solvent.
Triaziridine 8. Mitteilung. Zur Acylierung Von Dialkyl‐triaziridinen
Authors: Hilpert Hans , Hoesch Lienhard , Dreiding André S.
Published: December 2004

On the Acylation of Dialkyl‐triaziridines

(2,3‐trans)‐Diisopropyl‐ (1) and (2,3‐cis)‐1,3‐cyclopentylenetriaziridine (2) were reacted with ClCOOCH3. In the case of 1, with or without pyridine, an expected acylation at N(1) resulted in the methoxycarbonyl derivative 3. In the case of 2, the reaction in pyridine led to the γ‐ and α‐dihydropyridyl derivatives 5 and 6, respectively, where the acylpyridinium moiety had become attached by a ring C‐atom to N(1); without pyridine, it afforded the N‐cyclopentenylcarbamates 13 and 14by opening of the triaziridine ring and loss of N2. The mechanisms proposed for these reactions involve the initial attack of an electrophile at N(1) of 1 but at N(2) (or N(3)) of 2. This difference is rationalized with steric factors, inasmuch as the hindrance to an attack at N(2) (or (3)) is greater in i than in 2, whereas this hindrance at N(1) is smaller in 1 than in 2. The greater resistance to opening of the saturated N3‐homocycle during acylation of the monocyclic triaziridine 1, as compared to that of the tricyclic one 2, is attributed to greater strain in the latter system.
Copper and Silver Atoms in the β‐Cage of a Zeolite: Model Calculations
Authors: Calzaferri Gion , Forss Lars
Published: December 2004

The electronic structures of the 4‐4 SBU, the β‐cage, and the β‐cage with two 4‐4 SBU's attached to it have been studied by means of EH‐MO calculations. No indication of the formation of a band structure has been found. The HOMO region consists of many closely spaced, localized states, 98.6% of them concentrated on the O‐atoms. Reversible color changes of Cu+1 and Ag+1 zeolites observed upon hydration‐dehydration experiments can be understood as charge‐transfer transitions from the HOMO concentrated on the zeolite O‐atoms to the metal cations. As soon as the Cu+1 or Ag+1 are partially hydrated, the ns* and np* states are shifted to higher energies. The luminescence observed with dehydrated Cu+1‐zeolites X is caused by a 4p*←HOMO absorption, followed by spontaneous 4s*←4p* emission. After a detailed study of a Cu+1 in the 6‐6 SBU, we discuss the electronic structure of a β‐cage filled with 1,2,4,8, and 9 Cu+1. In each case, the β‐cage is found to be too small to allow the formation of a band structure. The levels caused by the added copper are distinctly quantized. Calculations on [Ag3(H2O)3]3+ in a β‐cage are reported. The direct interaction between the Ag‐atoms is significant. As a consequence, the states formed by Ag 5s and 5p atomic orbitals are delocalized over the three Ag‐centers. In both the Cu+1 and the Ag+1 zeolites, the ligand‐field picture is found to be insufficient to explain the electronic structure, when the metal is coordinated to the zeolite oxygen framework.
Chemical Degradation of Sarverogenin, Proof for the Presence of the Steroid Carbon Skeleton. Glycosides and Aglycones, 335th Communication
Authors: Lardon André , Reichsten Tadeus
Published: December 2004

Chemical degradation of sarverogenin (1) to several bile‐acid derivatives of known structures is described. This is a proof that 1 contains the normal tetracyclic steroid skeleton, and that the structure suggested for 1 by Fuhrer et al. [3] on the basis of spectral data is correct.
Drüsefarbstoffe aus Labiaten: Identifizierung von 17 Abietanoiden aus Plectranthus sanguineus BRITTEN
Authors: Matloubi‐Moghadam Firouz , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Pigments from Leaf‐Glands from Labiatae: 17 Quinonoid Abietanoids from Plectranthus sanguineus BRITTEN

From the glandular trichomes of the title plant from Nyasaland, Malawi, 17 abietanoid quinones and hydroquinones were isolated and identified, the most interesting amongst them being the novel tricyclic, sevenmembered anhydride 8. A detailed HPLC separation of the compounds is presented.
Octacarbonyldicoblat‐Inauced (1,3) H Shits in 1‐Methylallenecarboxylates and Allenic Lactones
Authors: Trifonov Latchezar S. , Orahovats Alaxander S. , Heimgartner Heinz
Published: December 2004

The allenecarboxylates 1a,b and allenic lactones 4a,b undergo thermally induced (1,3) H Shifts in the presence of Co2(CO)8. The non‐isolated 1,3‐dienes 2a,b react further affording the Diels‐Alder Adducts 3a,b Scheme 1 in high yields. These adducts were not formed in the case of the 2‐vinybutenolides 5a,b. On irradiationin the presence of Co2(CO)8 or Mn2(Co)10, the studied allenes reacted in a different manner, yielding either cyclization products 7 and 8 (Scheme 3) or products 9 and 10, formed via H abstracton and solvent addition (Schemes 4 and 5).
Chemie der α‐Aminonitrile 1. Mitteilung Einleitung und Wege zu Uroporphyrinogen‐octanitrilen
Authors: Ksander Gary , Bold Guido , Lattmann René , Lehmann Christian , Früh Thomas , Xiang Yi‐Bin , Inomata Katsuhiko , Buser Hans‐Peter , Schreiber Jakob , Zass Engelbert , Eschenmoser Albert
Published: December 2004

Chemistry of α‐Aminonitriles I: Introduction and Pathways to Uroporphyrinogen‐octanitriles.

An introduction to experimental studies on the chemistry of α‐aminonitriles potentially relevant to the problems of prebiotic chemistry is presented. The framework of conditions wherein the investigation is chosen to be carried out implies both molecular oxygen and ‐ whenever feasible ‐ water to be excluded from reaction conditions. This study focusses on 2‐amino‐2‐propenenitrile (3) (Scheme 6) as central starting material of reaction sequences which aim at the nitrile forms of proteinogenic amino acids as well as at the aza forms of building blocks of biological cofactor molecules as their targets (Scheme 5). Schemes 13,16,23 as well as 25 and 26 summarize reaction sequences by which 3 is transformed within the defined framework of conditions into the thermodynamic (statistically controlled) mixture of the four isomeric uroperphyrinogen‐octanitriles 57–60. HPLC's of such mixtures document the dominance of the least symmetrical isomer whose constitutional pattern of peripheral substituents happens to be the one percent in all biological porphinoids. Preparative procedures for the synthesis of 3(Scheme 9), the β,β‐disubstituted pyrrol‐nitriles 30,53 and 54 (Scheme 19) as well as the porphyrinogenoctakis(propionitrile) and‐octakis(acetonitrile) 65 and 66, respectively (Scheme 24) are given.
Enzyme‐Catalyzed Hydrolysis of Some Functionalized Dimethyl Malonates
Authors: Luyten Marcel , Müller Susanna , Herzog Beat , Keese Reinhart
Published: December 2004

A method is described for the preparation of (+)‐(R)‐methyl hydrogen 2‐(tert‐butoxymethyl)‐2‐methyl‐malonate (5e) in synthetically useful amounts from readily available starting material.
Synthesis of 12‐Methyl‐13‐tridecanolide
Authors: Stanchev Stephan , Hesse Manfred
Published: December 2004

The title compound was prepared from 2‐nitrocyclodecanone (2). Compound 2 was treated with 2‐methylpro‐penal to give the Michael‐addition product 3 which was reduced to the alcohol 5 and the latter ring‐enlarged with Bu4NF to 12‐methyl‐10‐nitro‐13‐tridecanolide (6) followed by reductive elimination of the NO2 group by Bu3SnH.
Synthesis of 2‐Cycloalkenones (Parts of 1,4‐Diacyl‐1,3‐butadiene Systems) and of a Heterocyclic Analogue by Metal‐Catalyzed Decomposition of 2‐Diazoacylfurans
Authors: Wenkert Ernest , Guo Ming , Pizzo Ferdinando , Ramachandran Kishore
Published: December 2004

Furans with side‐chains at C(2) of various lengths terminating in diazomethyl keto groups are shown to undergo Rh2(OAc)4‐catalyzed furan unravelling with the production of 2‐cyclopentenone, 2‐cyclohexenone, and 2‐cycloheptenone to each of whose olefinic C(β) is attached an acrylaldehyde unit. Interposition of a cyclohexane or a methylaminomethylene moiety between the furan and diazoketo functions leads to the formation of a hydroindenone and pyrrolone, respectively. Replacement of the diazomethylketo terminus by an α‐diazoethylketo system or a α‐diazo‐β‐keto‐ester function produces 2‐substituted 2‐cycloalkenones. A furan with a C4, diazo‐methylketo‐terminating side‐chain at C(3) is described to be transformed into a 4‐formylmethylidene‐2‐cyclohe‐xenone.
Preparation and C‐Alkylation of Enantiomerically Pure S‐Phenyl Aziridinecarbothioates. On the Structure of Small‐Ring Ester Lithium Enolates
Authors: Häner Robert , Olano Bernardo , Seebach Dieter
Published: December 2004

Racemic and enantiomerically pure methyl N‐(tert‐butyl)‐N‐benzyl‐ and N‐1‐(phenylethyl)aziridinecarboxylates are prepared by known methods and converted to phenyl thioesters (1, 2, 15, 16; Schemes 2 and 3). These are deprotonated with lithium diisopropylamide (LDA) and BuLi (for removal of diisopropylamine) in THF at dry‐ice temperature. The resulting lithiated species are surprisingly stable and are deuterated, alkylated (CH3, C2H5, allyl, benzyl), and added to aldehydes and nitroolefins in good yields (50–80 %, 18 examples; Schemes 1 and 4–6). The configurational stability of the lithiated species is studied, and conclusions about their structures are drawn. Thus, a C(α)‐lithiated ester (see L, Scheme 9) or an O‐lithiated ‘enolate’ (see M) with pyramidalized C(β)‐atom is proposed for the species from levorotatory S‐phenyl N‐benzylaziridinecarbothioate which does not undergo racemization after 1 h at −60° (THF solution).
New Antifungal Chromenyl Ketones and their Pentacyclic Dimers from Hypericum revolutum VAHL
Authors: Décostered Laurent A. , Hostettmann Kurt , Stoeckli‐Evans Helen , Msonthi Jerome D.
Published: December 2004

Two new 2H‐1‐benzopyranyl ketones 1 and 2 and three new pyrano[3,2‐c: 4,5,6‐d′ e′]di[1]benzopyrandiyl diketones 3, 4a/4b, and 5 have been isolated from the leaves and twigs of Hypericum revolutum VAHL (Guttiferae). The structure of 3 (hyperevoline) was established by X‐ray analysis as 1,1′‐[1,13,13a,13b‐tetrahydro‐5,8,10‐trihydroxy‐2,2,6,9,13,13‐hexamethyl‐2H, 7aH‐pyrano[3,2‐c:4,5,6‐d′e′]di[1]benzopyran‐4, 11‐diyl]bis[2‐methyl‐1‐propanone]. The structures of the isolated compounds were established by spectroscopic (UV, IR, EI‐MS, 1H‐ and 13C‐NMR) and chemical (acetylation and acidic dimerization) methods.
Acid‐Catalyzed Rearrangements of 5,6‐exo‐Epoxy‐7‐oxabicyclo[2.2.1]hept‐2‐yl Derivatives. Migratory Aptitudes of Acyl vs. Alkyl Groups in Wagner‐Meerwein Transpositions
Authors: Le Drian Claude , Vogel Pierre
Published: December 2004

In the presence of HSO3F/Ac2O in CH2CL2, 2‐exo‐ and 2‐endo‐cyano‐5,6‐exo‐epoxy‐7‐oxabicyclo[2.2.1]hept‐2‐yl acetates (6a, b) gave products derived from the epoxide‐ring opening and a 1,2‐shift of the unsubstituted alkyl group (σ bond C(3)–C(4)). In contrast, under similar conditions, the 5,6‐exo‐epoxy‐7‐oxabicyclo[2.2.1]heptan‐2‐one (6c) gave 5‐oxo‐2‐oxabicyclo[2.2.1]heptane‐3,7‐diyl diacetates 20 and 21 arising from the 1,2‐shift of the acyl group. Acid treatment of 5,6‐exo‐epoxy‐2,2‐dimethoxy‐7‐oxabicyclo[2.2.1]heptane (6d) and of 5,6‐exo‐epoxy‐2,2‐bis(benzyloxy)‐7‐oxabicyclo[2.2.1]heptane (6e) gave minor products arising from epoxide‐ring opening and the 1,2‐shift of σ bond C(3)–C(4) and major products (25, 29) arising from the 1,3‐shift of a methoxy and benzyloxy group, respectively. Under similar conditions, 5,6‐exo‐epoxy‐2,2‐ethylenedioxy‐7‐oxabicyclo[2.2.1]heptane (6f) gave 1,1‐(ethylenedioxy)‐2‐(2‐furyl)ethyl acetate (32, major) and a minor product 33, arising from the 1,2‐shift of σ bond C(3)–C(4). The following order of migratory aptitudes for 1,2‐shifts toward electron‐deficient centers has been established: acyl > alkyl > alkyl α‐substituted with inductive electron‐withdrawing groups. This order is valid for competitive Wagner‐Meerwein rearrangements involving equilibria between carbocation intermediates with similar exothermicities.
Mammalian Alkaloids: Configurations of Optically Active Salsoline‐ and 3′,4′‐Dideoxynorlaudanosoline‐1‐carboxylic Acids
Authors: Chrzanowska Maria , Schönenberger Bernhard , Brossi Arnold , Flippen‐Anderson Judith L.
Published: December 2004

Synthesis of the optical isomers of (±)‐methyl 6,7‐dimethyl‐3′,4′‐dideoxynorlaudanosoline‐1‐carboxylate ((±)‐2) was accomplished by reaction of (±)‐2 with (+)‐(R)‐1‐phenylethyl isocyanate, separation of the urea diastereoisomers (−)‐4A and (+)‐4B, and alcoholysis of the ureas in refluxing BuOH. Optically active isoquinoline‐carboxylates 2A,B and hydantoins 8A,B isolated were characterized. The absolute configuration of the reaction products was established by X‐ray analysis of the optically active hydantoin (+)‐8A. Hydrolysis of the methyl isoquinolinecarboxylates 2A,B with 48% HBr soln. at reflux afforded the desired optically active 3′,4′‐dideoxynorlaudanosoline‐1‐carboxylic acids 1A,B required for enzyme‐inhibition studies. Details of the X‐ray diffraction analysis of (+)‐methyl salsoline‐1‐carboxylate hydrobromide ((+)‐11A·HBr) prepared earlier are included. CD spectra of (+)‐(S)‐methyl 6,7‐dimethyl‐3′,4′‐dideoxynorlaudanosoline‐1‐carboxylate hydrobromide ((+)‐2A. HBr) and (−)‐(R)‐methyl salsoline‐1‐carboxylate hydrochloride ((−)‐11B·HCl) confirmed the assignment of their (S)‐ and (R)‐configurations, respectively.
Synthesis of 1,2‐five‐ring‐annellated barrelenes via the intramolecular Diels‐Alder reaction of acetylenic derivatives
Authors: Trifonov Latchezar S. , Orahovats Alexander S.
Published: December 2004

The intramolecular Diels‐Alder reaction conducted with acetylenic acylureas, obtained from carbodiimides, and the acetylenic acid 5 and its derivatives 13 gave the 1,2‐annellated barrelene 14 (from 13a) and the benzobarrelenes 8 (from 5) and 15 (from 13b); in the case of 3‐butynoic acid (1),[1,3]‐H shift were observed. The formation of the azabarrelenes 16 (from 13c) as an intermediate is postulated which looses HCN to afford the indolinone 17. The acylureas 6 and 9 underwent isocyanate cleavage instead of [4+2] cyclization.
General Synthesis of Ketones from Carboxylic Esters and Carboxamides by Use of Mixed Organolithium‐Magnesium Reagents: Syntheses of Artemisia Ketone
Authors: Fehr Charles , Galindo José , Perret Roland
Published: December 2004

The novel reagents formed by combination of Grignard reagents (RMgX) with lithium diisopropylamide (LDA) convert non‐enolizable or slowly enolizable carboxylic esters or caboxamides into ketones which are protected from further reaction by their in situ conversion into enolates. These enolates can be trapped with electrophiles such as Me3SiCl and allyl bromide. The scope of this Grignard mono‐addition is illustrated by two direct syntheses of artemisia ketone (14).