bluuebunny/crossref_metadata_2025 huggingface dataset:
Rhodium(II)‐Catalyzed Decomposition of β,γ‐Unsaturated Diazo Compounds
Authors: Motallebi Shahrokh , Müller Paul
Published: December 2004

The RhII‐catalyzed decomposition of β,γ‐unsaturated diazo ketones 1 in the presence of MeOH leads via vinylogous Wolff rearrangement to γ,δ‐unsaturated esters 6 (Schemes 1 and 2). A modest asymmetric induction is achieved when the reaction is carried out with chiral tetrakis(pyrrolidinecarboxylato)‐ or tetrakis(oxazolidinonato)dirhodium(II) complexes. Vinyl and phenyl diazoacetates 11 and 20, respectively, or 1‐diazo‐3‐phenyl‐propan‐2‐one (25), when subjected to the same reaction conditions, react by OH insertion with MeOH (Schemes 3–5). In the absence of MeOH, phenyl diazoacetates 20 and 25 undergo intramolecular CH insertion to 22 and 26, respectively. Intramolecular CH insertion occurs with N‐aryldiazoamides 23 even in the presence of MeOH (Scheme 5).
Synthesis and Electron‐Diffraction Structure of all‐cis‐[5.5.5.5]Fenestrane
Authors: Brunvoll Jan , Guidetti‐Grept Régine , Hargittai Istvan , Keese Reinhart
Published: December 2004

The efficient synthesis of all‐cis‐[5.5.5.5]fenestrane (2) from the readily available intermediate 3 allowed the electron‐diffraction analysis of 2. This structure analysis revealed long CC bonds in the central C(C)4 fragment and a twist‐envelope conformation for the four cyclopentane substructures. The four bridgehead H‐atoms are in a synclinal rather than an ecliptic position with an approximate D2 symmetry of 2. Planarizing distortions are evident from the opposite bond angles at the central C‐atom being 116.2 ± 0.5° with the remaining four being 103.7 ± 0.2°.
Thermal Reaction of Azulene‐1‐carbaldehydes with Dimethyl Acetylenedicarboxylate
Authors: Magnussen Anette , Uebelhart Peter , Hansen Hans‐Jürgen
Published: December 2004

Azulene‐1‐carbaldehydes which have Me substituents at C(3) and C(8) and no substituent at C(6) react with excess dimethyl acetylenedicarboxylate (ADM) in decalin at 200° to yield exclusively the Diels‐Alder adduct at the seven‐membered ring (cf. Scheme 3). The corresponding 1‐carboxylates behave similarly (Scheme 4). Azulene‐1‐carbaldehydes which possess no Me substituent at C(8) (e.g. 11, 12 in Scheme 2) gave no defined products when heated with ADM in decalin. On the other hand, Me substitutents at C(2) may also assist the thermal addition of ADM at the seven‐membered ring of azulene‐1‐carbaldehydes (Scheme 6). However, in these cases the primary tricyclic adducts react with a second molecule of ADM to yield corresponding tetracyclic compounds. The new tricyclic aldehydes 16 and 17 which were obtained in up to 50% yield (Scheme 3) could quantitatively be decarbonylated with [RhCl(PPh3)3] in toluene at 140° to yield a thermally equilibrated mixture of four tricycles (Scheme 8). It was found that the thermal isomerization of these tricycles occur at temperatures as low as 0° and that at temperatures > 40° the thermal equilibrium between the four tricycles is rapidly established via [1,5]‐C shifts. The establishment of the equilibrium makes the existence of two further tricycles necessary (cf. Scheme 8). However, in the temperature range of up to 85° these two further tricycles could not be detected by 1H‐NMR. When heated in the presence of excess ADM in decalin at 180°, the ‘missing’ tricyclic forms could be evidenced by their tetracyclic trapping products ‘anti’‐45 and ‘anti’‐48, respectively (Scheme 9).
Dicarboxylates of 3‐Methylidene‐β‐lactams: Addition Reactions to the Exocyclic Double Bond, Formation of Spiro‐β‐lactams, and Reductive Ring Opening by Hydrazines
Authors: Gürtler Susanne , Johner Michael , Ruf Sabine , Otto Hans‐Hartwig
Published: December 2004

O‐, S‐, and N‐Nucleophiles are added to the exocyclic double bond of the title compounds 1. The addition of O‐ or S‐nucleophiles yields stable products (Scheme 1), while addition of N‐nucleophiles results in thermally labile compounds (Scheme 2). The reaction is studied by spectroscopic methods. From hydrazine adducts, a spiro[azetidine‐3,3′‐pyrazolidine] 7 is obtained, and the addition products of methyl‐ and benzylhydrazine rearrange to pyrazol‐4‐carboxylates 6. Furthermore, the exocyclic double bond is used for the formation of spiro‐β‐lactams either by cyclopropane formation or by Diels‐Alder reactions (Scheme 4). The steric course of all reactions is studied, and it is shown that all reactions with the double bond occur from the side opposite to the bulkier substitutent at C(4) of the β‐lactam ring.
Metal complexes of macrocyclic ligands. Part XXXVII. Synthesis of Heteroditopic Bis‐macrocycles and Their Potential for Preparing Heterobinuclear Metal Complexes
Authors: Urfer André , Kaden Thomas A.
Published: December 2004

A new and generally applicable synthetic path for the preparation of heteroditopic bis‐macrocycles using tri‐N‐protected tetraazacycloalkanes as building blocks and bromoacetyl bromide as bridging reagent is described. In the first step, bromoacetyl bromide is used as acylating agent for one of the macrocycles, whereas in the second step it is used as alkylating agent for the second macrocycle, thus giving protected bis‐macrocyclic amides (e.g. 6). After reduction of the amide moiety and deprotection, bis‐azamacrocycles with an ethylene bridge are obtained (e.g. 8). The corresponding homoditopic bis‐macrocycles 16 and 17 are also prepared for comparison purpose. Spectrophotometric studies indicate that bis‐macrocycle 8, which consists of a 12‐ and a 14‐membered ring, binds two metal ions with equal affinity, whereas compound 13, in which an unsubstituted (cyclam) and a trimethyl‐substituted tetraazacyclotetradecane unit (Me3cyclam) are bridged, shows selective metal‐ion binding. The first metal ion is always incorporated into the cyclam unit, whereas the second one binds to the Me3cyclam macrocycle. Thus, by sequential addition of two different metal ions, heterobinuclear complexes can easily be prepared. The electrochemistry of the binuclear Ni2+ complexes, studied by CV and DPV, as well as the EPR spectra of the binuclear Cu2+ complexes clearly indicate metal‐metal interactions.
Thermoconversion of Caryophyllene‐ to Farnesene‐Type Sesquiterpenes. Short access to the enantiomers of (6RS,7RS)‐ and (6RS,7SR)‐6,7‐epoxy‐6,7‐dihydro‐β‐farnesenes
Authors: Giersch Wolfgang K. , Boschung André F. , Snowden Roger L. , Schulte‐Elte Karl H.
Published: December 2004

Flash‐vacuum thermolysis of the four diastereoisomeric 5,6‐epoxy‐5,6‐dihydro‐caryophyllenes 1–4 at 500–550°/0.1–0.7 Torr leads to the hitherto unreported enantiomers of (6RS,7RS)‐ and (6RS,7SR)‐6,7‐epoxy‐6,7‐dihydro‐β‐farnesenes ((±)‐5 and (±)‐6, resp.). In particular, (+)‐5 is formed in 45% yield (ca. 90% ee) and is, thus, an attractive chiral building block for natural‐product synthesis.
Antiparallel β‐Sheet Conformation in Cyclopeptides Containing a Pseudo‐amino Acid with a biphenyl moiety
Authors: Brandmeier Volker , Sauer Wolfgang H. B. , Feigel Martin
Published: December 2004

The biphenyl‐containing pseudo‐amino acids 2′‐(aminomethyl)biphenyl‐2‐carboxylic acid (Abc; 1) and 2′‐(aminomethyl)biphenyl‐2‐acetic acid (Aba; 2) are used as rigid spacers in the backbone of the cyclic peptides cyclo (‐Abc‐Ala‐Phe‐Gly‐)2 (5), cyclo(‐Abc‐Ala‐Val‐Gly‐)2 (6), cyclo(‐Aba‐Gly‐Phe‐Ala‐)2 (7), and cyclo(‐Aba‐Ala‐Phe‐Gly‐)2(8). Three different interconverting diastereoisomers are found in solutions of each of these cyclopeptides due to the atropisomerism of the biphenyl units. NMR Techniques and molecular‐dynamics calculations allow to conclude that the major diastereoisomer of 5 (and 6) in (D6)DMSO adopts a β‐sheet conformation. It is proposed that the pseudo‐amino acid 1 of (R)‐chirality forms, with attached L‐amino acids, a H‐bonding pattern comparable to a β‐turn (see D in Fig. 4 and F).
Vitamin‐B12‐katalysierte C,C‐Bindungsverknüpfung: Synthese von Jasmonaten via sequentielle Radikal‐Reaktion
Authors: Busato Stephan , Scheffold Rolf
Published: December 2004

Vitamin‐B12‐Catalyzed C, C‐Bond Formation: Synthesis of Jasmonates via Sequential Radical Reaction

The Cbl‐catalyzed electroreduction of 3‐(2′‐bromo‐1′‐ethoxyethoxy)cyclopenten (1a) in presence of 1‐cyanovinyl‐acetate (8) gave, in a sequential radical reaction (5‐exo‐trig‐cyclization of 1a followed by addition to 8), 1‐cyano‐2‐(2′‐ethoxy‐hexahydro‐2′H‐cyclopenta[b] furan‐4′‐yl)ethyl acetate (10a). This intermediate was transformed to methyl jasmonate (7; four steps) and epituberolide (9; three steps) in 20 and 31% yield, respectively, from cyclopent‐2‐en‐l‐ol.
The Structure of 1H‐Perimidin‐2(3H)‐one and Its Derivatives in the solid state (x‐ray crystallography and CP/MAS 13C‐NMR), in solution (13C‐NMR), and in the gas phase (mass spectrometry)
Authors: Claramunt Rosa M. , Dotor Julio , Sanz Dionisia , Foces‐Foces Concepción , Llamas‐Saniz Antonio L. , Elguero José , Flammang Robert , Morizur Jean Pierre , Chapon Erik , Tortajada Jeanine
Published: December 2004

The X‐ray crystal and molecular structures of 1‐methyl‐ 1H‐perimidin‐2(3H)‐one (5b) and 1,3‐dimethyl‐1H‐perimidin‐2(3H)‐one (6) were determined. The crystals are built of piles of dimers faced head‐to‐head in 5b and of alternating independent head‐to‐tail molecules in 6, both along the b axis. Semiempirical calculations at the AM 1 level revealed that the eclipsed conformation of the Me groups with respect to the CO group, found in the crystals, is the most stable. The lack of planarity of the whole molecules is a consequence of the packing forces since it is not found in the calculations. A comparative NMR study was carried out in solution (1H and 13C) and in the solid state (CP/MAS 13C) for 1H‐perimidin‐2(3H)‐one (2) and 1H‐benzimidazol‐2(3H)‐one (3) with the conclusion that in both heterocycles the oxo tautomer is the most abundant. The structure in the gas phase was approached by mass spectrometry. In the case of 3, the oxo tautomer loses CO after ionization, while the oxo form of 2 tautomerizes to the hydroxy form which loses, H2O after a [1,3]‐H shift. AM 1 calculations were carried out on the ground and ionized states of 2.
Nucleophilic Substitution in the Allylic System of Codeine and Pseudocodeine: Reactions with lithium cyano(methyl)‐and (aryl)cyanocuprates. Crystal and molecular structure of 8α‐phenyl‐6,7‐didehydro‐4,5α‐epoxy‐3‐methoxy‐17‐methylmorphinan and 6α‐phenyl‐7,8‐didehydro‐4,5α‐epoxy‐3‐methoxy‐17‐methylmorphinan
Authors: Kalinin Valery N. , Belyakova Irina L. , Derunov Vladimir V. , Petrovskii Pavel V. , Yanovski Aleksandr I. , Struchkov Yurii T. , Schmidhammer Helmut , Park Jin K.
Published: December 2004

Nucleophilic substitution of 6β‐chloro‐7,8‐didehydro‐4,5α‐epoxy‐3‐methoxy‐17‐methylmorphinan (1) and 8α‐bromo‐6,7‐didehydro‐4,5α‐epoxy‐3‐methoxy‐17‐methylmorphinan (2) with lithium cyano(methyl)‐ and (aryl)cyanocuprates(I) (5a–c) was accompanied by allylic rearrangement with both change and retention of orientation of the substituting group (Scheme 1, Table 1). Nucleophilic substitution in 7,8‐didehydro‐4,5α‐epoxy‐3‐methoxy‐17‐methylmorphinan‐6α‐yl methanesulfonate (3) and 7,8‐didehydro‐4,5α‐epoxy‐3‐methoxy‐17‐methylmorphinan‐6β‐yl methanesulfonate (4) proceeded without allylic rearrangement with both change and retention of the orientation of the substituting group (Scheme 2, Table 1). X‐Ray diffraction studies of the products 6,7‐didehydro‐4,5α‐epoxy‐3‐methoxy‐17‐methyl‐8α‐phenylmorphinan (6b) and 7,8‐didehydro‐4,5α‐epoxy‐3‐methoxy‐17‐methyl‐6β‐phenylmorphinan (7b) were carried out (Figs. 1 and 2).
NMR of Terminal Oxygen. Part 14. Kinetically stabilized simple enols containing methylated uracil groups: Application of a 17O‐NMR test of H‐bonding
Authors: Zhuo Jin‐Cong , Wyler Hugo , Péchy Peter , Dahn Hans
Published: December 2004

In the crystalline N,N′‐dimethylated uracil derivatives 2a, b, the kinetically stabilized enol group forms an H‐bond with OC(4), as demonstrated by increased shielding of specifically labelled 2a and 2b in the 17O‐NMR spectra (Δδ(17O)(C(4)—O)  −30 ppm); absence of dilution and solvent effects show that the H‐bridge is intra‐molecular, forming an eight‐membered chelate ring. The (apparent) shielding effect Δδ(17O) in 2a, b is larger than that in salicylamide. The strong H‐bond explains why the enols 2, in spite of the absence of steric hindrance, are kinetically stabilized.
Organic Diodes Based on Redox‐Polymer Bilayer‐Film‐Modified Electrodes
Authors: Zhao Wenyuan , Marfurt Judith , Walder Lorenz
Published: December 2004

The synthesis of four electropolymerizable 2,2′‐bipyridinium salts with tuned reduction potential (E1∘) is described (N,N′‐ethylene‐4‐methyl‐4′‐vinyl‐2,2′‐bipyridinium dibromide (4; E1∘ –0.48 V), 4‐methyl‐N, N′‐(trimethylene)‐4′‐vinyl‐2,2′‐bipyridinium dibromide (5; E1∘ −0.66 V), N,N′‐ethylene‐4‐methyl‐4′‐[2‐(1H‐pyrrol‐1‐yl)ethyl]‐2, 2′‐bipyridinium bis(hexafluorophosphate) (6b; E1∘ −0.46 V), and 4‐methyl‐4′‐[2‐(1H‐pyrrol‐1‐yl)ethyl]‐N, N′‐(trimethylene)‐2,2′‐bipyridinium bis(hexafluorophosphate) (7b; E1∘ −0.66 V)). E1∘‐Tuning is based on the torsional angle C(3)–C(2)–C(2′)–C(3′), imposed by the N,N′‐ethylene and N,N′‐(trimethylene) bridge. The vinylic compounds 4 and 5 undergo cathodic, the pyrrole derivatives 6b and 7b anodic electropolymerization on glassy carbon electrodes from MeCN solutions, yielding thin, surface‐confined films with surface concentrations of redox‐active material in the range 5 · 10−9 < Γ < 2.10−8 mol/cm2, depending on experimental conditions. The modified electrodes exhibit reversible ‘diquat’ electrochemistry in pure solvent/electrolyte. Copolymerization of 6b or 7b with pyrrole yields most stable electrodes. Bi ayer‐film‐modified electrodes were prepared by sequential electropolymerization of the monomers. The assembly electrode/poly‐6b/poly‐7b behaves as a switch, it transforms – as a Schmitt trigger – an analog input signal (the electrode potential) into a digital output signal (redox state of the outer polymer film). Forward‐(electrode/poly‐7b/poly‐6b) and reverse‐biased assemblies (electrode/poly‐6b/poly‐7b) were coupled to the electrochemical reduction of redox‐active solution species, e.g. N‐ (cyanomethyl)‐N′‐methyl‐4,4′‐bipyridinium bis(hexafluorophosphate) (8). Zener‐diode‐like behavior was observed. Aspects of redox‐polymer multilayer‐film assemblies, sandwiched between two electronic conductors, are discussed in terms of molecular electronic devices.
Synthesis of oligoribonucleotides containing isoguanosine
Authors: Seela Frank , Fröhlich Thomas
Published: December 2004

Oligoribonucleotides containing isoguanosine (  1,2‐dihydro‐2‐oxoadenosine; isoG;1) were prepared. The building block2was synthesized using the (dimethylamino)methylidene residue as NH2protecting group. The monomethoxytrityl as well as dimethoxytrityl group were introduced at OH–C(5′) (→5and6). Silylation of5with triisopropylsilyl chloride formed the 2′‐O‐blocked derivative7almost exclusively. Reaction with PCl3/1,2,4‐1H‐triazole furnished the phosphonate2which was used in solid‐phase synthesis of the oligoribonucleotides10and11. RNAse T1hydrolyzed U‐A‐G‐U‐U‐isoG‐U‐U‐A‐G (10) at the 3′‐site of G but not of isoG. The self‐complementary oligomer (A‐U‐isoG‐U)3(11) formed a duplex which was less stable than that of (A‐U)6.
New C2‐Chiral Bidentate Ligands Bridging the gap between donor phosphine and acceptor carbonyl ligands
Authors: Peter Kündig E. , Dupré Chantal , Bourdin Bernadette , Cunningham Allan , Pons Dominique
Published: December 2004

Two new C2 chiral bidentate phosphorous ligands have been prepared in enantiomerically pure form. The two phosphorous centers bear electron‐withdrawing groups ((CF3)2CHO, C6F5) and are linked by a trans‐cyclopentane‐1,2‐diol‐derived bridge. Photolysis of [Cr(η6‐C6H6)(CO)3] in the presence of these two new ligands and of two previously reported bidentate phosphites, and fluorophosphinites (L) afforded [Cr(η6‐C6H6)(CO)L] complexes. IR Spectral comparison of the complexes shows the new ligands to be intermediate in their bonding properties between alkyl phosphites and CO.
Metal Complexes of Pentadentate Macrocyclic Ligands Containing Oxygen and Nitrogen as Donor Atoms
Authors: Cabral M. Fátima , Delgado Rita
Published: December 2004

Four macrocyclic ligands have been synthesized: 1‐oxa‐4,7,10,13‐tetraazacyclopentadecane (1), 1,4‐dioxa‐7,10,13‐triazacyclopentadecane (2), 1,4‐dioxa‐7,11,14‐triazacyclohexadecane (3), 1,4‐dioxa‐7,11,15‐triazacycloheptadecane (4), one of them 3, for the first time. The protonation constants of the ligands and the stability constants of the complexes formed by the four ligands with some divalent first‐series transition‐metal ions, Cd2+ and Pb2+, were determined by potentiometric methods, in aqueous solution, at 25° and I = 0.10M (KNO3). The sequence of protonation of ligand 1 was studied by 1H‐NMR spectroscopy. The Irving‐Williams' order of stability is obeyed for the complexes of all the ligands, and the metal complexes of 1 present the higher values of stability. A drop in the stability of all the metal complexes studied is observed when the metal complexes of 1 are compared with the corresponding complexes of 2. The effect of the increase of the ring size of the macrocycle can be observed for metal complexes of the series of ligands 2 4, where, in spite of the slight increase of the overall basicity of the ligands (20.28, 22.25, and 24.96 for 2, 3, and 4 respectively), small differences in stability are found for the corresponding complexes of 2 and 3, but a significant drop occurs for all the metal complexes formed with the 17‐membered ligand, specially for the larger metal ions like Mn2+ and Pb2+.
Synthesis and Conformational Analysis of 2′‐Deoxy‐2′‐(3‐methoxybenzamido)adenosine, a rational‐designed inhibitor of trypanosomal glyceraldehyde phosphate dehydrogenase (GAPDH)
Authors: Van Calenbergh Serge , Van Den Eeckhout Elfride , Herdewijn Piet , De Bruyn André , Verlinde Christophe , Hol Wim , Callens Mia , Van Aerschot Arthur , Rozenski Jef
Published: December 2004

A series of 2′‐benzamido‐2′‐deoxyadenosine analogues were synthesized in an effort to find new lead structures for the treatment of sleeping sickness. The 2′‐deoxy‐2′‐(3‐methoxybenzamido)adenosine (1h) was proved to be a selective inhibitor of the parasite glyceraldehyde 3‐phosphate dehydrogenase which confirms the modeling studies. The solution‐state conformation of 2′‐(thiophene‐2‐carboxamido) analogue 1d demonstrates a 2′‐endo conformation, an orientation of the thiophene ring under the ribose moiety, and the base part occupying a ‘syn’/‘anti’ equilibrium.
Organic Reactions in the Solid State: The reactivity of guest molecules in tri‐o‐thymotide clathrates
Authors: Gerdil Raymond , Barchietto Giacomo
Published: December 2004

Tri‐o‐thymotide (TOT) clathrates are enantiomorphous and enantioselective (chiral cages). It was shown that an external molecular reactant can diffuse into the TOT host crystal lattice and reacts with the included molecule (guest) in characteristic ways, differing from those occurring in liquid solutions. Several aspects of the action of hydrogen halides (HCl, HBr) on the chemical behavior of included oxiranes were investigated for solid‐gas and solid‐liquid (aqueous) systems. Under well established experimental conditions, these reactions gave regiospecifically one target product and were asymmetric. The included substrate underwent first an acid‐catalyzed allylic isomerization that is cage‐specific and mostly quantitative. In sheer contrast, strong basic conditions were required to promote, in reduced yield, the analogous transformation in solution. The regiospecificity and enantioselectivity of several intra‐crystalline conversions allowed the accurate determination of the absolute configuration of several guest molecules. Kinetic measurements were achieved that disclosed some striking features of this new type of heterogeneous reactions. Tentative models for the cage stereoselective mechanisms are briefly discussed.
Macrocyclische Imide: Vielseitige Synthese‐Bausteine bei Ringerweiterungsreaktionen
Authors: Koch Thomas , Hesse Manfred
Published: December 2004

Macrocyclic Imides: Versatile Synthons in Ring‐Enlargement Reactions

Macrocyclic imides differ from phthal‐ or succinimids in their increased electrophilicity. This property makes them versatile synthons for reactions with several nucleophiles. If a nucleophile is attached to the N‐substituent of the imide, an intramolecular reaction will occur leading to ring‐enlarged products. Use of N, O, and C nucleophiles for this synthetic pathway is reported. Synthetic transformations of e.g. cyclododecanone leads to 17‐, 18‐, or 19‐membered macrolides, 11, 12, 15, 16, 21, 27, 30, in three to five steps.
N4‐Benzoylspermidine from Oncinotis tenuiloba: Analytical differentiation of the three isomeric N‐benzoylspermidines
Authors: Doll Martin K.‐H. , Guggisberg Armin , Hesse Manfred
Published: December 2004

During the examination of extracts from Oncinotis tenuiloba STAPF a new polyamine, N4‐benzoylsperimidine (8), was isolated. For unambiguous structure elucidation, it was transformed into the diacetyl derivative 13, and the three possible N‐benzoyl‐substituted isomers of spermidine 5, 8, and 11 together with their peracetylated derivatives 12–14, respectively, were synthesized and identified.
Synthesis of the Thiazolone Analogue of the Acetylcholinesterase Inhibitor, Huperzine A
Authors: Kozikowski Alan P. , Tückmantel Werner , Saxena Ashima , Doctor Bhupendra P.
Published: December 2004

The preparation of an analogue 3a of the acetylcholinesterase inhibitor, huperzine A (1), is described in which the pyridinone moiety of the natural product is replaced with a thiazolone moiety. The synthesis started from cyclohexane‐1,4‐dione monoethylene ketal (7) by first annulating the thiazole ring using the Gewald protocol (→ 8; Scheme 1) and then constructing the bicyclo[3.3.1]nonane substructure using our previously described Michael addition/aldol condensation methodology (Scheme 3). The central problem was the protection of the thiazolone carbonyl group; only the 2‐unsubstituted thiazole survived the reaction conditions of the first half of the synthesis. Refunctionalization was later effected by lithiation and subsequent chlorination with hexachloroethane (30→31). Compound 3a was ineffective in the acetylcholinesterase inhibition assay in concentrations up to 14 μM.
A Reinvestigation of the Oxidative Rearrangement of Yohimbane‐Type Alkaloids. Part A. Formation of pseudoindoxyl ( = 1,2‐dihydro‐3H‐indol‐3‐one) derivatives
Authors: Stahl Reto , Borschberg Hans‐Jürg
Published: December 2004

Contrary to earlier reports, the base‐induced rearrangement of the 7‐hydroxy‐7H‐indolenines derived from ajmalicine (1), yohimbine (5), corynanthine (6), methyl reserpate (16), and methyl isoreserpate (17) in each case furnished not just one, but two epimeric spiro‐pseudoindoxyl derivatives which have opposite configuration at the spiro centre C(2). In all cases, the major component was shown by NOE experiments to be the A‐type isomer (carbonyl group located below the plane defined by rings C and D). The thermodynamically less stable B‐type pseudoindoxyl epimers 4, 10, 12, and 22 were isolated and characterized for the first time.
On the Stacking of β ‐Rings: The solution self‐association behavior of two partially N‐methylated cyclo(hexaleucines)
Authors: Sun Xicheng , Lorenzi Gian Paolo
Published: December 2004

Cyclo(‐D‐Leu‐L‐MeLeu‐D‐Leu‐L‐MeLeu‐D‐Leu‐L‐MeLeu‐) (1) and cyclo(‐L‐Leu‐D‐Leu‐L‐MeLeu‐D‐Leu‐L‐Leu‐D‐Leu‐) (2) were synthesized and used for a study of the interaction of β ‐rings in solution. In appropriate solvents, 1 and 2 formed dimers consisting of two β ‐rings connected through six interannular H‐bonds and having the N ‐Me group(s) on the solvent‐exposed face. The study also afforded indications that 2 formed different dimers of this kind, differing in the relative orientation of the two β ‐rings. These experimental observations provide strong support to the idea that unsubstituted D,L‐alternating cyclooligopeptides, such as cyclo(hexaleucine), can self‐assemble and give rise to long tubular stacks of β ‐rings.
Permanganate Oxidation of Quinoxaline and Its Derivatives
Authors: Obafemi Craig A. , Pfleiderer Wolfgang
Published: December 2004

The oxidation reactions of a series of quinoxaline derivatives, using KMnO4 in the presence or absence of NaOH, are described. Neutral oxidation of 2‐chloro‐ and 2, 3‐dichloroquinoxalines 2–4 afforded the corresponding chloro‐ and dichloropyrazinedicarboxylic acids 13 and 14 in good yield. On the other hand, oxidation of quinoxalin‐2(1H)‐one and 1, 4‐dihydroquinoxaline‐2, 3‐dione derivatives in alkaline medium gave different products, with the quinoxalin‐2(1H)‐one (5) forming 1, 4‐dihydroquinoxaline‐2, 3‐dione (9), while various substituted quinoxalin‐2, 3‐dione derivatives (see 9–11) gave a new type of dimeric products. The structural assignments for the new compounds were based on spectroscopic data.
Synthesis of 3‐Methoxy‐ and 3‐(β‐D‐Glucopyranosyloxy)flavylium Ions. Influence of the flavylium substitution pattern on the reactivity of anthocyanins in aqueous solution
Authors: Dangles Olivier , Elhajji Hakima
Published: December 2004

The synthesis of 3‐glycosyloxylated flavylium ions (anthocyanins), in particular of callistephin (4), a natural anthocyanin, is described. The structural transformations in aqueous solution and molecular complexation with chlorogenic acid (7) and caffeine (8) of the synthesized pigments 3 and 4 are investigated and compared to those of the corresponding 3‐methoxyflavylium ions 1 and 2 and to those of oenin (5) and malvin (6), two very common natural anthocyanins. The results are discussed in terms of the role played by the glycosyloxy residues in the chemical properties of anthocyanins. Anthocyanin molecular complexation (copigmentaion) is quantitatively investigated by UV/VIS spectroscopy and 1H‐NMR. In particular, the UV/VIS spectroscopic data are interpreted using a general theoretical treatment, which, e.g., allows to demonstrate the formation of molecular complexes between the colourless forms of an anthocyanin and 8.
Synthesis and Characterization of New Phthalocyanines Peripherally Fused to Four 13‐Membered Tetrathiamacrocycles
Authors: Gürek Ayşe G. , Bekâroǧlu özer
Published: December 2004

The new metal‐free phthalocyanine 5 and phthalocyaninatometals 6–8 (M=Co, Ni, or Zn) fused in peripheral positions with four 13‐membered tetrathiamacrocycles were prepared by cyclotetramerization of 2, 3, 6, 7, 9, 10‐hexahydro‐5H‐[1, 4, 8, 11]benzotetrathiacyclotridecine‐13, 14–dicarbonitrile in the presence of a suitable metal salt or a strong organic base. In contrast to the aza‐ or oxamacrocycle‐fused analogs, the solubility of these phthalocyanines is very low. Complexation of the tetrathiamacrocycles of 7 and 8 with PdII or AgI to form pentanuclear products was accomplished from their suspensions.
Rhodenthoside A, a New Type of Acylated Secoiridoid Glycoside from Gentiana rhodentha
Authors: Ma Wei‐Guang , Fuzzati Nicola , Wolfender Jean‐Luc , Hostettmann Kurt , Yang Chong‐Ren
Published: December 2004

Investigation of the metabolites from Gentiana rhodentha FR. (Gentianaceae) by LC‐UV and LC‐MS resulted in the isolation and identification of a new type of secoiridoid glycoside, rhodenthoside A (1), together with the known secoiridoids sweroside (2) and swertiamarin (3), as well as the known iridoids kingiside (4) and 8‐epikingiside (5). The structures were established by 1D‐ and 2D‐NMR, EI‐MS, D/CI‐MS, FAB‐MS, CF‐FAB, LC‐MS, TSP, LC‐MS, and LD‐MS data in combination with chemical reactions.
Metal‐Ion‐Coordinating Properties of a Viral Inhibitor, a pyrophosphate analogue, and a herbicide metabolite, a glycinate analogue: The solution properties of the potentially five‐membered chelates derived from phosphonoformic acid and (aminomethyl)phosphonic acid
Authors: Song Bin , Chen Dong , Bastian Matthias , Sigel Helmut , Bruce Martin R.
Published: December 2004

The pyrophosphoric‐acid‐analogue phosphonoformic acid (pfa) and the amino‐acid‐analogue (aminomethyl)phosphonic acid (ampa) both form, in the deprotonated state, i.e., as –OOC–PO and H2NCH2PO, respectively, five‐membered chelate rings with metal ions. pfa inhibits both phosphate transport and virus replication, while ampa is a metabolic product of the common herbicide glyphosate (  N‐(phosphonomethyl)glycine). The acidity constants of H2pfa– and H2ampa± as well as the stability constants of the [M(Hpfa)], [M(pfa)]–, [M(Hampa)]+, and [M(ampa)] complexes, where M2+  Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Cu(2,2′‐bipyridyl)2+, Cu(1,10‐phenanthroline)2+, Zn2+, or Cd2+, have been determined by potentiometric pH titrations in aqueous solution at 25° and I  0.1M (NaNO3). The structures of isomeric complexes and the connected intramolecular equilibria are deduced and evaluated based on the equilibrium constants measured and those calculated via the pKa values of the above mentioned ligands and previously established log K vs. pKa straight‐line plots (H. Sigel et al., Helv. Chim. Acta 1992, 75, 2634) for a simple phosphonate‐M2+ coordination. pfa forms stronger complexes than ampa with all the above mentioned metal ions, with the single exception of [Cu(ampa)] which is slightly more stable than [Cu(pfa)]–. In neutral solutions, more precisely at pH of ca. 6, pfa complexes of alkaline‐earth‐metal ions retain one phosphonate‐bound proton, [M(Hpfa)], while those of the transition‐metal ions chelate with the trianionic ligand, pfa3–. In accord with increasing ligand‐basicity, the stability‐constant order for all metal‐ion complexes is oxalate > pfa > pyrophosphate but, owing to proton competition in pyrophosphate, in neutral solutions metal‐ion complexation of pfa3– competes with P2O. With ampa alkaline‐earth‐metal ions interact only with the phosphonate group of even the dianionic ligand (though Mg2+ appears to form a low fraction of a [Mg(ampa)] chelate) while transition‐metal ions form chelates which are comparable in stability to those of glycinate.
Synthesis and Complexation Properties of a New Class of Receptors based on a cone‐configurated tetra‐p‐(tert‐butyl)calix[4]arene and bipyridyl subunits
Authors: de Vains Jean‐Bernard Regnouf , Lamartine Roger
Published: December 2004

0The bipyridyl‐armed tetra‐p‐(tert‐butyl)calix[4]arenes 1–5 were synthesized from tetra‐p‐(tert‐butyl)‐calix[4]arene A and 6‐(bromomethyl)‐6′‐methyl‐2,2′‐bipyridine (B) by direct base‐strength‐driven regioselective O‐alkylation or by stepwise procedures. Preliminary complexation studies of the ligands 1–3 with CuI affording the complexes 6–8 are described.
A New Triterpene Saponin from Heteropappus biennis with an Unusual Carbohydrate Chain
Authors: Bader Gerd , Danzandarjaa Tuja , Hiller Karl , Reznicek Gottfried , Jurenitsch Johann , Golly Monika , Schröder Harald , Schubert‐Zsilavecz Manfred , Haslinger Ernst
Published: December 2004

A new saponin, O‐α‐D‐arabinopyranosyl‐(1→6)‐O‐[α‐L‐rhamnopyranosyl‐(1→2)]‐O‐[β‐D‐xylopyranosyl‐(1→3)]‐β‐D‐glucopyranosyl arjunolate (1) was isolated from the flowers of Heteropappus biennis (LDB.) TAMAMSCH. The structure was established mainly by a combination of 1D selective and 2D NMR techniques like COSY, TOCSY, ROESY, HMQC, and HMBC. Molecular‐modelling calculations showed that the oligosaccharide chain is rather rigid. Six minimum structures are discussed.
Preparation and Structure of Oligolides from (R)‐3‐Hydroxypentanoic Acid and comparison with the hydroxybutanoic‐acid derivatives: A small change with large consequences
Authors: Seebach Dieter , Hoffmann Torsten , Kühnle Florian N. M. , Lengweiler Urs D.
Published: December 2004

Cyclic oligomers of (R)‐3‐hydroxyvaleric acid (3‐HV) are prepared from the monomer by three different methods, giving various ratios of the oligomers. The macrocycles containing three to twelve 3‐HV units (12‐ to 48‐membered rings) are isolated in pure form by chromatography. The triolide 3 can be separated by distillation and isolated on large scale. Biopol, the copolymer of (R)‐3‐hydroxybutanoic acid (3‐HB) and (R)‐3‐hydroxyvaleric acid (3‐HV), is degraded to mixtures of Me‐ and Et‐substituted triolides (‘mixolides’) with high crystallization tendency. The X‐ray crystal structures of the tetrolide 4, pentolide 5, hexolide 6, heptolide 7, and of two ‘mixolides’ (with inclusions of solvent) have been determined (Figs. 3–7, 10, and 11) and are compared with those of the corresponding 3‐HB derivatives reported previously. From the structural data, a 31 and a 21 helix of 3‐HV can be modelled, and the latter one compared with helix structures of P9(3‐HB) and P(3‐HV) derived from stretch‐fibre X‐ray scattering. Crystals of a water‐containing NaSCN complex of the triethyl triolide 3 were obtained in good quality for X‐ray analysis. The structure (Figs. 12, 13, and Table 6) contains an interesting array of CO and H2O O‐atoms around the Na+ ions along a channel‐type tube (a‐axis of the crystal) which may be relevant to the role of P(3‐HB) and P(3‐HV) as components of cellular ion channels.
Synthesis of Tri‐, Penta‐, and Heptapeptides Containing and (R)‐2‐alkyl‐2‐amino‐3‐(methylamino)‐propionic acid residue in the central position
Authors: Seebach Dieter , Studer Armido , Pfammatter Elmar , Widmer Hans
Published: December 2004

By conventional peptide‐coupling methods (C to N direction; mixed anhydride, bis(2)‐oxooxazolidin‐3‐yl)phosphinoyl chloride (Bop‐Cl), or dicyclohexylcarbodiimide (DCC), 2‐amino‐2‐methyl‐3‐(methylamino)‐propionic acid and 2‐amino‐2‐ethyl‐3‐(methylamino)propionic acid ( = 2‐amino‐2‐[(methylamino)methyl]butanoic acid) are incorporated in the central position of tri‐, penta‐, and heptapeptides (see 3–7, 21, and 22). The fragment coupling of the β ‐amino group of the diamino‐acid moiety in a tetrapeptide led to partial epimerization, and thus, two epimeric heptapeptide derivatives were actually obtained (7 and epi‐7). The final deprotection to the free heptapeptide (involving a Me3SiI cleavage of BocNH and MeOCONH, a saponification with NaOH, and HPLC purification) gave both the desired product (isopeptide 21), with the β ‐amino group inside the peptide backbone, and a product (peptide 22) of transpeptidation, with the α‐amino group of the diamino acid incorporated and a (methylamino)methyl group as the side chain. Peptide 22 is completely converted to the isopeptide 21 by prolonged treatment with base. The heptapeptide 21 was analyzed by elaborate 2QF‐COSY and NOESY NMR measurements in H2O/CD3OD at −5° (Table, Fig.); there is no indication for β ‐sheet or helical structures, a fact which was also confirmed by CD measurements.
Chemie von α‐Aminonitrilen. 12. Mitteilung. Sondierungen über thermische Umwandlungen von α‐Aminonitrilen
Authors: Xiang Yi‐Bin , Drenkard Susanne , Baumann Karl , Hickey Deirde , Eschenmoser Albert
Published: December 2004

Chemistry of α‐Amino Nitriles

11. Mitteilung: [1].

.
Exploratory Experiments on Thermal Reactions of α‐Amino Nitriles

The paper extends a previously published report [4] on chemical properties of α‐amino nitriles and of members of the C3H4N2 ensemble (Scheme 1) as observed in experiments carried out under non‐aqueous conditions. The reactions investigated and the observations made are summarized in some detail in the English footnotes (*) referring to Schemes 1–17 and Fig. 1.
Hetero‐Diels‐Alder Additions of α,β‐Unsaturated‐Acyl Cyanides. Part 3. Syntheses of 3‐bromo‐2‐ethoxy‐3,4‐dihydro‐2H‐pyran‐6‐carbonitriles, and about their transformation to 2‐ethoxy‐2H‐pyrans
Authors: Zhuo Jin‐Cong , Wyler Hugo , Schenk Kurt
Published: December 2004

Cycloadditions of the α,β‐unsaturated‐acyl cyanides 1–3 with (Z)‐or (E)‐1‐bromo‐2‐ethoxyethene (4) may be performed at moderate temperatures and provide in good yields the 3‐bromo‐2‐ethoxy‐3,4‐dihydro‐2H‐pyran‐6‐carbonitriles 5–7, respectively (Scheme 1). Diastereoisomeric pairs of products result at room temperature merely from the ‘endo’‐ and ‘exo’‐transition states; more complex mixtures appear above 60° as a consequence of (Z)/(E)‐isomerization of 4. The relative stability of the anomers of 5 and 6 is explored by treatment with BF3·Et2O. Acid alcoholysis (MeOH or EtOH) of 5 leads to acetals 9a, b of 4‐bromo‐5‐oxopentanoate. Alkyl (2Z,4E)‐5‐ethoxypenta‐2,4‐dienoates 12, 17, and 20, are formed in alcoholic alkoxide solutions from 5, 6, and 7, respectively, which is compatible with the intermediacy of 2‐alkoxy‐2H‐pyrans and their valence tautomers, α,β‐unsaturatedacyl cyanides. Methoxide addition to the CN group competes with dehydrobromination in case of 5; it leads to 3‐bromo‐3,4‐dihydro‐2H‐pyran‐6‐carboximidate 13 (ca. 50% at −20°) which can be hydrolyzed to the methyl carboxylate 14. DBU (1,8‐diazabicyclo[5,4,0]undec‐7‐ene) in benzene converts 5 to 6‐ethoxy‐2‐oxohexa‐3,5‐dienenitrile (11), the ring‐opening product of an obviously unstable 2‐ethoxy‐2H‐pyran; the same reagent dehydrobrominates 6 to 2‐ethoxy‐4‐methyl‐2H‐pyran‐6‐carbonitrile (15). HBr Elimination from 7 takes place with great ease in presence of pyridine, or even during chromatography on alumina, and leads to the stable ethyl 6‐cyano‐2‐ethoxy‐2H‐pyran‐4‐carboxylate (18); this dimerizes at room temperature to give a 1:3 mixture of tricyclic adducts ‘endo’‐21 and ‘exo’‐21. The structure of the latter is established by an X‐ray crystallographic analysis.
Preparation and Absolute Configuration of Some Iris Essential Oil Constituents of the 5‐methylsafranic‐acid series
Authors: Chapuis Christian , Schulte‐Elte Karl H.
Published: December 2004

The β‐dienoate (+)‐(5S)‐13a (86% ee; meaning of α and β as in α‐ and β‐irone, resp.) was obtained from (−)‐(5S)‐9a via acid‐catalyzed dehydration of the diastereoisomer mixture of allylic tertiary alcohols (+)‐(1S,5S)‐15/(+)‐(1R,5S)‐15 (Scheme 3). Prolonged treatment gave clean isomerization via a [1,5]‐H shift to the α‐isomer (−)‐(R)‐16a with only slight racemization (76% ee; Scheme 4). In contrast, the SnCl4‐catalyzed stereospecific cyclization of (+)‐(Z)‐6 to (−)‐trans‐8a (Scheme 2), followed by a diastereoselective epoxidation to (+)‐11 gave, via acid‐catalyzed dehydration of the intermediate allylic secondary alcohol (−)‐12, the same ester (+)‐13a (Scheme 3), but with poor optical purity (13% ee), due to an initial rapid [1,2]‐H shift. The absolute configuration of (−)‐16a–c was confirmed by chemical correlation with (−)‐trans‐19 (Scheme 4). 13C‐NMR Assignments and absolute configurations of the intermediate esters, acids, aldehydes, and alcohols are presented.
Absolute Rate Constants for the Addition of Cyanomethyl (·CH2CN) and (tert‐Butoxy)carbonylmethyl (·CH2CO2C(CH3)3) radicals to alkenes in solution
Authors: Wu Jie Qiang , Beranek Ivan , Fischer Hanns
Published: December 2004

Absolute rate constants and their temperature dependence were determined by time‐resolved electron spin resonance for the addition of the radicals ·CH2CN and ·CH2CO2C(CH3)3 to a variety of mono‐ and 1,1‐disubstituted and to selected 1,2‐ and trisubstituted alkenes in acetonitrile solution. To alkenes CH2CXY, ·CH2CN adds at the unsubstituted C‐atom with rate constants ranging from 3.3·103 M−1S−1 (ethene) to 2.4·106 M−1S−1 (1,1‐diphenylethene) at 278 K, and the frequency factors are in the narrow range of log (A/M−1S−1) = 8.7 ± 0.3. ·CH2CO2C(CH3)3 shows a very similar reactivity with rate constants at 296 K ranging from 1.1·104 M−1S−1 (ethene) to 107 M−1S−1 (1,1‐diphenylethene) and frequency factors log (A/M−1S−1) = 8.4 ± 0.1. For both radicals, the rate constants and the activation energies for addition to CH2CXY correlate well with the overall reaction enthalpy. In contrast to the expectation of an electro‐ or ambiphilic behavior, polar alkene‐substituent effects are not clearly expressed, but some deviations from the enthalpy correlations point to a weak electrophilicity of the radicals. The rate constants for the addition to 1,2‐ and to trisubstituted alkenes reveal additional steric substituent effects. Self‐termination rate data for the title radicals and spectral properties of their adducts to the alkenes are also given.
Enantioselective Allylic Substitution Catalyzed by Chiral [Bis(dihydrooxazole)]palladium Complexes: Catalyst structure and possible mechanism of enantioselection
Authors: Matt Peter Von , Lloyd‐Jones Guy C. , Minidis Alexander B. E. , Pfaltz Andreas , Macko Ludwig , Neuburger Markus , Zehnder Margareta , Rüegger Heinz , Pregosin Paul S.
Published: December 2004

Allylpalladium complexes with chiral bis(dihydrooxazole) ligands were studied as catalysts for the enantioselective allylic substitution reaction of rac‐1,3‐diphenylprop‐2‐enyl acetate (rac‐5) with the anion of dimethyl malonate (Scheme 1). Using enantiomerically pure (S,E)‐1‐(4‐tolyl)‐3‐phenylprop‐2‐enyl acatete ((S)‐25) as substrate, the reaction was shown to proceed by a clean ‘syn’ displacement of acetate by dimethyl malonate (Scheme 6). The [Pd11(η3‐allyl)] complex 18 and the analogous [Pd(η3‐1,3‐diphenylallyl)] complex 20, both containing the same bis(dihydrooxazole) ligand, were characterized by X‐ray structure analysis and by NMR spectroscopy in solution. The structural data reveal that steric interactions of the allyl system with the chiral ligand result in selective electronic activation of one of the allylic termini. The higher reactivity of one allylic terminus toward nucleophilic attack is reflected in a significantly longer PdC bond and a shift of the corresponding 13C‐NMR resonance to higher frequency.
Synthesis of Polypropionate Fragments Containing Tertiary‐Alcohol Moieties. Cross‐aldolisations with lithium enolates of 7‐oxabicyclo[2.2.1]heptan‐2‐one derivatives
Authors: Kernen Philippe , Vogel Pierre
Published: December 2004

The Diels‐Alder adduct of 2,4‐dimethylfuran to 1‐cyanovinyl (1′R)‐camphanate ((+)‐(1R,2S,4R)‐2‐exo‐cyano‐1,5‐dimethyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐endo‐yl (1′R)‐camphanate ((+)‐1)) was converted into (+)‐2,7‐dideoxy‐2,4‐di‐C‐methyl‐L‐glycero‐ ((+)‐6) and ‐D‐glycero‐L‐altro‐heptono‐1,4‐lactone ((+)‐7), into (−)‐(3R,4R,5R,6S)‐3,4:5,7‐bis(isopropylidenedioxy)‐4,6‐dimethylheptan‐2‐one ((−)‐22), and into (+)‐(2R,3R,4R,5S,6S)‐3,4:5,6‐bis(isopropylidenedioxy)‐2,4‐dimethylheptanal ((+)‐34). Condensation of ((+)‐34 with the lithium enolate of (−)‐(1R,4R,5S,6R)‐6‐exo‐[(tert‐butyl)dimethylsilyloxy]‐1,5‐endo‐dimethyl‐7‐oxabicyclo[2.2.1] heptan‐2‐one ((−)‐38; derived from (+)‐1) gave a 3:2 mixture of aldols (+)‐39 and (+)‐40 (mismatched pairs of a α‐methyl‐substituted aldehyde and (E)‐enolate) whereas the reaction of (±)‐34 with (±)‐38 gave a 10:1 mixture of aldols (±)‐41 and (±)‐39. A single aldol, (−)‐44, was obtained to condensing (+)‐34 with the lithium enolate of (+)‐(1S,4S,5S,6S)‐5‐exo‐(benzyloxy)‐1,5‐endo‐dimethyl‐7‐oxabicyclo[2.2.1]heptan‐2‐one ((+)‐43; derived from (−)‐(1S,2R,4S)‐2‐exo‐cyano‐1,5‐dimethyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐endo‐yl (1′S)‐camphanate ((−)‐3)). All these cross‐aldolisations are highly exo‐face selective for the bicyclic ketones. The best stereochemical matching is obtained when the lithium enolates and α‐methyl‐substituted aldehydes can realize a ‘chelated transition state’ that obeys the Cram and Felkin‐Anh models (steric effects). Polypropionate fragments containing eleven contiguous stereogenic centres and tertiary‐alcohol moieties are thus prepared with high stereoselectivity in a convergent fashion. The chiral auxiliaries ((1R)‐ and (1S)‐camphanic acid) are recovered at the beginning of the syntheses.
Synthesis of a Masked p ‐Quinone Methide β ‐Lactam as an active metabolite of nocardicins
Authors: Hakimelahi Gholam H. , Tsay Shwu‐Chen , Hwu Jih Ru
Published: December 2004

Nocardicin A analogues 30, 34, and 38 as well as the highly strained quinone methide 43 were synthesized. β ‐Lactam 34 was found biologically active against several Gram‐negative microorganisms in vitro; pyridinium N‐oxide derivative 38 possessed activity against Gram‐positive S. aureus bacterium. Masked p‐quinone methide β ‐lactam 43 exhibited significant antimicrobial activity in vitro. A mechanism involving an oxidation in vivo is proposed for the unprecedented biological properties of nocardicins.
Synthese von Tetradecano‐14‐lacton durch Ringerweiterung
Authors: Kostova Kalina , Hesse Manfred
Published: December 2004

Synthesis of Tetradecano‐14‐lactone by Ring Enlargement

The aldehyde 3, prepared by ozonolysis of 2‐allyl‐2‐nitrocyclododecanone, gave the ring‐enlargement product 5(85%) by treatment with (i‐Bu)2AlH. Its transformation to the tetradecano‐14‐lactone (8) via the aldol ester 6 and other routes (best is reduction with Bu3SnH, AlBN, toluene) was difficult. Remarkable is the smooth denitrification of 3 (loss of HNO2) to the conjugated dione 4 by chromatography on silica gel or base treatment.
The Decomposition of cis‐Fused Cyclopenteno‐1,2,4‐Trioxanes induced by Ferrous Salts and some oxophilic reagents
Authors: Jefford Charles W. , Favarger France , Vicente Maria Da Graça H. , Jacquier Yvan
Published: December 2004

Two cis‐fused cyclopenteno‐1,2,4‐trioxanes, 1a and 1b, were subjected to Zn in AcOH or FeCl2 · 4H2O in MeCN. In the first case, the main course was deoxygenation to give cyclopentanone (18) and the 1,4‐diphenyl‐ or 1,4‐bis(4‐fluorophenyl)cyclopent‐3‐ene‐1,2‐diol 10 (Scheme 5). In the second case, isomerization chiefly occurred resulting in the formation of a dimer 9 of the respective 3,5‐diaryl‐5‐hydroxycyclopent‐2‐enyl 5‐hydroxypentanoates 8 (Scheme 3).
Ein neuer Zugang zu 2′‐O‐Alkylribonucleosiden und Eigenschaften deren Oligonucleotide
Authors: Martin Pierre
Published: December 2004

A New Access to 2′‐O‐Alkylated Ribonucleosides and Properties of 2′‐O‐Alkylated Oligoribonucleotides

A general access to 2′‐O‐alkylated ribonucleosides using the key intermediate 5 is presented. The incorporation of 2′‐O‐‘ethyleneglycol’‐ and 2′‐O‐‘glycerol’‐substituted (i.e., 2′‐O‐(2‐hydroxyethyl)‐ and 2′‐O‐(2,3‐dihydroxypropyl)‐substituted) ribonucleosides into oligonucleotides affords a new generation of oligonucleotides with high affinity for RNA, high specificity, and increased nuclease resistance.
Syntheses of the Enantiomers of γ‐Cyclogeranic Acid, γ‐Cyclocitral, and γ‐Damascone: Enantioselective protonation of enolates
Authors: Fehr Charles , Galindo José
Published: December 2004

(R)‐and (S)‐γ‐cyclogeranic acid ((R)‐and (S)‐9, resp.) were obtained by resolution of the racemate, and their absolute configurations determined by chemical correlation. The γ‐acids (R)‐and (S)‐9 were converted into (R)‐and (S)‐methyl γ‐cyclogeranate ((R)‐and (S)‐6, resp.), and (R)‐and (S)‐γ‐damascone ((R)‐and (S)‐5, resp.). A more direct entry to (R)‐and (S)‐9 consisted in the enantioselective protonation of a thiol ester enolate with (−)‐ or (γ)‐N‐isopropylephedrine((−)‐ or (γ)‐20) and subsequent hydrolysis of the (R)‐and (S)‐S‐phenyl γ‐thiocyclogeranate ((R)‐ and (S)‐24, resp.; 97% ee). The esters (R)‐ and (S)‐24 were also used as precursors of (R)‐ and (S)‐γ‐damascone ((R)‐ and (S)‐5, resp.). Alternatively, (S)‐5 (75% ee) was obtained by enantioselective protonation of ketone enolate 29 with (−)‐N‐isopropylephedrine ((−)‐20). Organoleptic evaluation demonstrated that the (S)‐enantiomers of methyl γ‐cyclogeranate and γ‐damascone are markedly superior to their (R)‐enantiomers.
First Use of Benzyl Phosphites in the Michaelis‐Arbuzov Reaction synthesis of mono‐, Di‐, and triphosphate analogs
Authors: Saady Mourad , Lebeau Luc , Mioskowski Charles
Published: December 2004

Benzyl phosphites were used in the Micaelis‐Arbuzov reaction. Special experimental conditions allowed preparation of a set of phosphonate analogs of mono‐, di‐, and triphosphate. Furthermore, regioselective monodeprotection makes these molecules useful building blocks for the synthesis of analogs of polyphosphorylated compounds of biological interest (e.g. nucleotides), after removal of all phosphonate benzyl ester groups under very mild conditions and high yields.