bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel and Efficient Approach for the Combinatorial Synthesis of Structurally Diverse Pyrimidines on solid support
Authors: Obrecht Daniel , Abrecht Christine , Grieder Alfred , Villalgordo José M.
Published: December 2004

We describe a versatile novel approach for the synthesis of 2, 4, 6‐trisubstituted pyrimidines on solid support. Thus, polymer‐boun J thiouronium salt 2 reacted in high yield in a cyclocondensation reaction with the acetylenic ketones 3 to form, after tert‐butyl‐ester cleavage, the polymer‐bound carboxylic acids 4, which were cleaved by oxidation with 3‐chloroperbenzoic acid and pyrrolidine to form the 2‐pyrrolidinylpyrimidine‐4‐carboxylic acids 6a‐c in high yields and purities without further purification (Scheme 1). Alternatively, acid 4a was subjected to an Ugi four‐component condensation which gave the polymer‐bound Ugi products 9a‐e in good yields (Scheme 2). Multidirectional cleavage reaction of sulfone 8a with different nucleophiles resulted in the clean formation of pyrimidine‐4‐carboxamides 10–13 (Scheme 3). This strategy combines efficiently solid‐phase chemistry with a multicomponent reaction and a multidirectional cleavage step to form highly diverse pyrimidines in a parallel array.
Lanthanide Complexes of Polyacid Ligands derived from 2, 6‐bis(pyrazol‐1‐yl)pyridine, pyrazine, and 6, 6′‐bis(pyrazol‐1‐yl)‐2, 2′‐bipyridine: Synthesis and luminescence properties
Authors: Rodriguez‐Ubis Juan Carlos , Sedano Rosa , Barroso Gemma , Juanes Olga , Brunet Ernesto
Published: December 2004

The synthesis of three novel pyrazole‐containing complexing acids, N,N,N′,N′‐{2, 6‐bis[3‐(aminomethyl)pyrazol‐1‐yl]‐4‐methoxypyridine}tetrakis(acetic acid)(1), N,N,N′,N′‐{2, 6‐bis[3‐(aminomethyl)pyrazol‐1‐yl]pyrazine}‐tetrakis(acetic acid) (2), and N,N,N′,N′‐{6, 6′‐bis[3‐(aminomethyl)pyrazol‐1‐yl]‐2, 2′‐bipyridine}tetrakis(acetic acid) (3) is described. Ligands 1–3 formed stable complexes with EuIII, TbIII, SmIII, and DyIII in H2O whose relative luminescence yields, triplet‐state energies, and emission decay lifetimes were measured. The number of H2O molecules in the first coordination sphere of the lanthanide ion were also determined. Comparison of data from the EuIII and TbIII complexes of 1–3 and those of the parent trisheterocycle N,N,N′,N′‐{2, 6‐bis[3‐(aminomethyl)pyrazol‐l‐yl]pyridine}tetrakis(acetic acid) showed that the modification of the pyridine ring for pyrazine or 2, 2′‐bipyridine strongly modify the luminescence properties of the complexes. MeO Substitution at C(4) of 1 maintain the excellent properties described for the parent compound and give an additional functional group that will serve for attaching the label to biomolecules in bioaffinity applications.
The Diyne Reaction of 3, 3′‐Bis(phenylethynyl)‐2, 2′‐bithiophene Derivatives via Rhodium Complexes: A novel approach to condensed benzo[2, 1‐b :3, 4‐b′]dithiophenes
Authors: Dahlmann Uwe , Neidlein Richard
Published: December 2004

The syntheses of benzo‐fused benzo[2, 1‐b:3, 4‐b′]dithiophenes 1 and benzo[2, 1‐b:3, 4‐b′:5, 6‐c″]trithiophenes 2 are described. The treatment of easily available 3, 3′‐bis(phenylethynyl)‐2, 2′‐bithiophene derivatives 5a and 6 (via PdII‐catalyzed alkynylation of the corresponding 3, 3′‐dibromo‐2, 2′‐bithiophenes; see Scheme 1) with chlorotris‐(triphenylphosphine)rhodium(I) yields the corresponding cyclic rhodium complexes 7 (Scheme 2) which smoothly react with acetylenes and sulfur to give 1 and 2 in good yields (Schemes 3–5).
Configurational Description of Chiral Fullerenes and Fullerene Derivatives with a Chiral Functionalization Pattern
Authors: Thilgen Carlo , Herrmann Andreas , Diederich François
Published: December 2004

Simple recommendations for the configurational description of chiral fullerenes and fullerene derivatives with a chiral functionalization pattern are presented in detail and illustrated with examples for different types of compounds. The descriptor system is based on the fact that the numbering schemes proposed for fullerenes are chiral (helical) and, thus, constitute an ideal reference for differentiating between enantiomers of chiral carbon cages and of fullerene derivatives with a chiral functionalization pattern. A single descriptor is sufficient to specify the configuration of the chiral spheroids, regardless of their functionalization degree. According to the helicity of the numbering scheme to be used, the descriptors are fC (clockwise) or fA (anticlockwise). The proposed configurational description can also be extended to related classes of compounds such as chiral bowl‐shaped condensed ring systems and their derivatives with a chiral functionalization pattern.
Binuclear Copper(II) Complexes with Robsori‐Type Ligands. Synthesis, characterization, crystal structure, and magnetic properties
Authors: Cheng Peng , Liao Daizheng , Yan Shiping , Cui Jianzhong , Jiang Zonghui , Wang Genglin , Yao Xinkan , Wang Honggen
Published: December 2004

Three binuclear copper(II) complexes, [Cu2(μ‐L)(μ‐N3)](ClO4)2′ 1‐5 EtOH (1), [Cu2(μ‐L)(μ‐MeO)(ClO4)]‐ClO4 ‐ EtOH (2) and [Cu2(μ‐L)(μ‐C3H3N2)](ClO4)2 · 2H2O, (3) where L is the pentadentale bridging ligand derived from 5‐(tert‐butyl)‐2‐hydroxybenzene‐1, 3‐dicarbaldehyde bis(benzoylhydrazone) (HL) were synthesized and characterized. The crystal‐structure determination of complex 2 provided the following crystal data: monoclinic, space group P21}/a, a = 11.412(2), b = 24.509(4), c = 14.833(4) Å, β = 104.41(2)°, K = 4018(3) Å3, Z = 4. The structure shows that the CuII ions are bridged by the endogenous phenolato O‐atom and by an exogenous bridge CH3O−. The analysis of variable‐temperature magnetic susceptibility data (4‐300 K.) indicates that there is an antiferromagnetic interaction between the CuII ions in these complexes with an exchange parameter (2J) of −119.1 cm−1 for complex 1 and −361.8 cm−1 for complex 3. The effect of some exogenous bridging ligands on magnetic coupling for this type of complex is suggested.
New Heptalenes Substituted with Extended π‐Systems
Authors: Houar Sarah El , Hansen Hans‐Jürgen
Published: December 2004

The synthesis of π‐substituted heptalenecarboxylates or ‐dicarboxylates, starting with the easily available dimethyl 9‐isopropyl‐1, 6‐dimethylheptalene‐4, 5‐dicarboxylate (2b), are described. Treatment of 2b with t‐BuOK and C2Cl6 at −78° leads to the chemoselective introduction of a Cl substituent in Me‐C(1) (see 5b in Scheme 1). Formation of the corresponding triphenylphosphonium salt 7b via the iodide 6b (Scheme 2) allowed a Wittig reaction with cinnamaldehyde in the two‐phase system CH2Cl2/2N NaOH. Transformation of the 4, 5‐dicar‐boxylate of 2b into the corresponding pseudo‐ester 10b allowed the selective reduction of the carbonyl function at C(4) with DIBAH to yield the corresponding 4‐carbaldehyde 11b (Scheme 3). Wittig reaction of 11b with (benzyl) triphenylphosphonium bromide led to the introduction of the 4‐phenylbuta‐1, 3‐dienyl substituent at C(4). The combination of both Wittig reactions led to the synthesis of the 1, 4‐bis(4‐phenylbuta‐1, 3‐dienyl)‐substituted heptalene‐5‐carboxylate (all‐E)‐17b (Scheme 5). In a similar manner, by applying a Horner‐Wadsworth‐Emmons reaction, followed by the Wittig reaction, the donor‐acceptor substituted heptalene‐5‐carboxylate (E;E)‐22b was synthesized (Scheme7). Most of these new heptalenes are in solution, at room temperature, in thermal equilibrium with their double‐bond shifted (DBS) isomers. In the case of (all‐E)‐17b and (E;E)‐22b, irradiation of the thermal equilibrium mixture with light of λ ‐(439 ± 10) nm led to a strong preponderance ( > 90%) of the DBS isomers 17a and (E;E)‐22a, respectively (Schemes 6 and 7). Heating of the photo‐mixtures at 40° re‐established quickly the thermal equilibrium mixtures. Heptalenes‐carboxylates (all‐E)‐17a and (E;E)‐22a which represent the off‐state of a 1,4‐conjugative switch (CS) system show typical heptalene UV/VIS spectra with a bathochromically shifted heptalene band III and comparably weak heptalene bands II and I which appear only as shoulders (Figs. 4 and 5). In contrast, the DBS isomers (all‐E)‐17b and (all‐E)‐22b, equivalent to the on‐state of a 1,4‐CS system, exhibit extremely intense heptalene bands I and, possibly, II which appear as a broad absorption band at 440 and 445 nm, respectively, thus indicating that the CSs (all‐E)‐17a⇌(all‐E)‐17b and (E;E)‐22a⇌(E;E)‐22b are perfectly working.
Methanofullerene Molecular Scaffolding: Towards C60‐substituted poly(triacetylenes) and expanded radialenes, preparation of a C60–C70 hybrid derivative, and a novel macrocyclization reaction
Authors: Nierengarten Jean‐Franjois , Herrmann Andreas , Tykwinski Rik R. , Riittimann Markus , Diederich Francois , Boudon Corinne , Gisselbrecht Jean‐Paul , Gross Maurice
Published: December 2004

The synthesis of (E)‐hex‐3‐ene‐l, 5‐diynes and 3‐methylidenepenta‐1, 4‐diynes with pendant methano[60]‐fullerene moieties as precursors to C60‐substituted poly(triacetylenes) (PTAs, Fig. 1) and expanded radialenes (Fig. 2) is described. The Bingel reaction of diethyl (E)‐2, 3‐dialkynylbut‐2‐ene‐1, 4‐diyl bis(2‐bromopropane‐dioates) 5 and 6 with two C60 molecules (Scheme 2) afforded the monomeric, silyl‐protected PTA precursors 9 and 10 which, however, could not be effectively desilylated (Scheme 4). Also formed during the synthesis of 9 and 10, as well as during the reaction of C60 with thedesilylated analogue 16 (Scheme 5), were the macrocyclic products 11, 12, and 17, respectively, resulting from double Bingel addition to one C‐sphere. Rigorous analysis revealed that this novel macrocyclization reaction proceeds with complete regio‐ and diastereoselectivity. The second approach to a suitable PTA monomer attempted N, N′‐dicyclohexylcarbodiimide(DCC)‐mediated esterification of (E)‐2, 3‐diethynylbut‐2‐ene‐l, 4‐diol (18, Scheme 6) with mono‐esterified methanofullerene‐dicarboxylic acid 23; however, this synthesis yielded only the corresponding decarboxylated methanofullerene‐carboxylic ester 27 (Scheme 7). To prevent decarboxylation, a spacer was inserted between the reacting carboxylic‐acid moiety and the methane C‐atom in carboxymethyl ethyl 1, 2‐methano[60]fullerene‐61, 61‐dicarboxylate (28, Scheme 8), and DCC‐mediated esterification with diol 18 afforded PTA monomer 32 in good yield. The formation of a suitable monomeric precursor 38 to C60‐substituted expanded radialenes was achieved in 5 steps starting from dihydroxyacetone (Schemes 9 and 10), with the final step consisting of the DCC‐mediated esterification of 28 with 2‐[1‐ethynyl(prop‐2‐ynylidene)]propane‐1, 3‐diol (33). The first mixed C60‐C70 fullerene derivative 49, consisting of two methano[60]fullerenes attached to a methano[70]fullerene, was also prepared and fully characterized (Scheme 13). The Cs‐symmetrical hybrid compound was obtained by DCC‐mediated esterification of bis[2‐(2‐hydroxy‐ethoxy)ethyl] 1, 2‐methano[70]fullerene‐71, 71‐dicarboxylate (46) with an excess of the C60‐carboxylic acid 28. The presence of two different fullerenes in the same molecule was reflected by its UV/VIS spectrum, which displayed the characteristic absorption bands of both the C70 and C60 mono‐adducts, but at the same time indicated no electronic interaction between the different fullerene moieties. Cyclic voltammetry showed two reversible reduction steps for 49, and comparison with the corresponding C70 and C60 mono‐adducts 46 and 30 indicated that the three fullerenes in the composite fullerene compound behave as independent redox centers.
Synthesis of Indole Derivatives by [2 + 2] Photocycloaddition of Indoline‐2‐thiones with alkenes and photodesulfurization of indoline‐2‐thiones
Authors: Nishio Takehiko , Oka Mitsuru
Published: December 2004

The photochemical synthesis of indole derivatives starting from the indoline‐2‐thiones 1 is described. Irradiation of indoline‐2‐thiones 1 in the presence of alkenes 3 gave 2‐alkyl‐3H‐indoles 4–7 or 2‐alkylindoles 8–22 through the ring cleavage of the intermediates, spirocyclic amino‐thietanes, initially derived by [2 + 2] cycloaddition of the CS bond of 1 and the CC bond of 3. Irradiation of 1 in the presence of trialkylamines 26 gave desulfurization products 27–32 and unexpected 3‐alkylindoles 33–40. N‐Acylindoline‐2‐thiones 11‐p yielded the deacylated products, indoline‐2‐thiones 1a‐b, and ethyl esters 43 through γ‐H abstraction by the excited thioamide S‐atom when irradiated in CDC13/EtOH or benzene/EtOH. Oxygen analogues 2a‐d also underwent intramolecular H abstraction to give the indolin‐2‐ones 2e–f and ethyl esters 43 in a similar way.
C45‐ and C50‐Carotehoids. Part 8. Synthesis of (all‐E,2S,2′S)‐bacterioruberin, (all‐E,2S,2′S)‐monoanhydrobacterioruberin, (all‐E,2S,2′S)‐bisanhydrobacterioruberin, (all‐ E,2R,2′R)‐3,4,3′,4′‐tetrahydrobisanhydro‐ bacterioruberin, and (all‐E,S)‐2‐isopentenyl‐3,4‐dehydrorhodopin
Authors: Lakomy Ivo , Sarbach Daniel , Traber Bruno , Arm Christoph , Zuber Daniel , Pfander Hanspeter , Noack Klaus
Published: December 2004

Starting from (R)‐3‐hydroxybutyric acid ((R)‐10) the C45‐ and C50‐carotenoids (all‐E,2S,2′S)‐bacterioruberm (1), (all‐E,2S,2′S)‐monoanhydrobacterioruberin (2), (all‐E,2S,2′S)‐bisanhydrobacterioruberin (3), (all‐E,2R,2′R)‐3,4,3′,4′‐tetrahydrobisanhydrobacterioruberin (5), and (all‐E,S)‐2‐isopentenyl‐3,4‐dehydrorhodopin (6) were synthesized. By comparison of the chiroptical data of the natural and the synthetic compounds, the (2S)‐ and (2′S)‐configuration of the natural products 1–3 and 6 was established.
A Novel Approach towards 2,3,5‐Trisubstituted Thiophenes via tandem Michael addition/intramolecular Knoevenagel condensation
Authors: Obrecht Daniel , Gerber Fernand , Sprengeir Daniel , Masquelin Thierry
Published: December 2004

Starting from the easily available, highly functionalized acetylenic ketories 4a–i (Scheme 1), novel 2,3,5‐trisubstituted thiophenes 1a–i (Scheme 2) were synthesized in good yields using a tandem Michael‐addition/intramolecular Knoevenagel‐condensation strategy, featuring Cs2CO3/MgSO4 (1:2) as an efficient base to effect the cyclization. Subsequent simple one‐step transformations yielded 2,3‐disubstituted thiophene‐5‐carbaidehydes 7a–c, carboxylic‐acid derivatives 8, 9, and 11, and alcohol 10 (Scheme 3). These molecules constitute interesting novel thiophene‐containing building blocks, useful for the preparation of low‐molecular‐weight compound libraries by combinatorial and parallel‐chemistry techniques.
Solid‐Phase Total Synthesis of Cyclosporine Analogues
Authors: Ko Soo Y. , Wenger Roland M.
Published: December 2004

Syntheses of cyclosporine analogues are reported wherein the peptide couplings were achieved in solid phase. The Wang resin was used as the solid support, and the peptide couplings commenced with the residue 11 of the cyclosporine skeleton. The couplings proceeded in a stepwide manner up to the residue MeBmt1, using symmetric anhydrides. The peptides were then cleaved off the resin, and the cyclization was achieved in solution using Castro's reagent. The solid‐phase synthesis described herein offers a very efficient method for the rapid synthesis of structurally diverse cyclosporine analogues in small quantities. The biological activities of the synthetic cyclosporine analogues were evaluated in two in vitro assays, including the IL‐2 reporter gene assay and the cyclophilin binding assay. The structure‐activity relationship is discussed.
Metal Complexes with Macrocyclic Ligands. PartXLV Axial coordination tendency in reinforced tetraazamacrocyclic complexes
Authors: Kowallick Ralph , Neuburger Markus , Zehnder Magareta , Kaden Thomas A.
Published: December 2004

The Cu2+ and Ni2+ complexes of three reinforced tetraazamacrocycles, containing a piperazine subunit and one or two alkyl substituents at the other two N‐atoms have been prepared and their structural properties studied. In solution, the Ni2+ complexes are square‐planar and show no tendency to axially coordinate a solvent molecule or an N ion. In contrast, the Cu2+ complexes change their geometry depending upon the donor properties of the solvent, being square‐planar in MeNO2 and pentacoordinate in DMF. They also easily react in aqueous solution with N to give ternary species with pentacoordinate geometry, the stabilities of which have been determined. In the solid state, the X‐ray crystal structures of three Cu2+ complexes also show both geometrical arrangements, two having a square‐planar, the other one a distorted square pyramidal geometry. The difference behavior of Ni2+ and Cu2+ stems from the fact that the structural change from square‐planar to square‐pyramidal can easily be accomplished for Cu2+, whereas, for Ni2+, it is accompanied by an electronic rearrangement from the low‐spin to the high‐spin configuration. The relatively rigid ligands cannot Adapt to the somewhat larger high‐spin Ni2+ion.
1,3‐Dipolare Cycloadditionen eines Carbonyl‐ylids mit 1,3‐Thiazol‐5(4H)‐thionen und Thioketonen
Authors: Meier Karl‐Richard , Linden Anthony , Heimgartner Heinz , Mlostoń Grzegorz
Published: December 2004

1,3‐Dipolar Cycloadditions of a Carhonyl‐ylide with 1,3‐Thiazole‐5(4H)‐thiones and Thioketones

Inp‐xylene at 150°, 3‐phenyloxirane‐2,2‐dicarbonitrile (4b) and 2‐phenyl‐3‐thia‐1‐azaspiro[4.4]non‐1‐ene‐4‐thione (1a) gave the three 1:1 adduets trans‐3a, cis‐3a, and 13ain 61, 21, and 3% yield, respectively (Scheme 3). The stereoisomers trans‐3a and cis‐3a are the products of a regioselective 1,3‐dipolar cycloaddition of carbonylylide 2b, generated thermally by an electrocyclic ring opening of 4b (Scheme 6), and the CS group of 1a. Surprisingly, 13a proved not to be a regioisomeric cycloadduct of 1a and 2b, but an isomer formed via cleavage of the OC(3) bond of the oxirane 4b. A reaction mechanism rationalizing the formation of 13a is proposed in Scheme 6. Analogous results were obtained from the reaction of 4b and 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazole‐5 (4H)‐thione (1b, Scheme 3). The thermolysis of 4b in p‐xylene at 130° in the presence of adamantine–thione (10) led to two isomeric 1:1 adducts 15 and 16 in a ratio of ca. 2:1, however, in low yield (Scheme 4). Most likely the products are again formed viathe two competing reaction mechanisms depicted in Scheme 6. The analogous reactions of 4b with 2,2,4,4‐tetramethylcyclobutane‐1,3‐thione (11) and 9H‐xanthene‐9‐thione (12) yielded a single 1:1 adduct in each case (Schemes). In the former case, spirocyclic 1,3‐oxathiolane 17, the product of the 1,3‐dipolar cycloaddition with 2a corresponding to 3a, was isolated in only 11 % yield. It is remarkable that no 2:1 adduct was formed even in the presence of an excess of 4b. In contrast, 4b and 12 reacted smoothly to give 18 in 81 % yield; no cycloadduct of the carbonylylide 2a could be detected. The structures of cis‐3a, 13a, 15, and 18, as well as the structure of 14, which is a derivative of trans‐3a, have been established by X‐ray crystallography (Figs. 1–3, Table).
Non‐destructive Removal of the Bornanesultam Auxiliary in α‐Substituted N‐Acylbornane‐10,2‐sultanis under Mild Conditions: An efficient synthesis of enantiomerically pure ketones and aldehydes
Authors: Oppolzer Wolfgang , Darcel Christophe , Rochet Patrick , Rosset Stephane , De Brabander Jef
Published: December 2004

α‐Substituted N‐acylbornane‐10, 2‐sultams 6, 9, and 10 can be converted into enantiomerically pure ketones 5. 13, and 14, respectively, via a two‐step procedure involving a known mercaptolysis reaction followed by an [Fe(acac)3]‐mediated coupling of the resulting S‐benzyl thioesters with Grignard reagents. Furthermore, enantiomerically pure aldehydes 23 can be obtained from α‐substituted N‐acylbornane‐10,2‐sultams 6 via a one‐step reduction with (i‐Bu)2AIH. No epimerization at the α‐chiral center is observed during the cleavage reaction whereby the chiral auxiliary, bornane‐10,2‐sultam 1 or ent‐l, was recovered. By using this methodology, several natural products or precursors thereof can be prepared.
Breakdown of Chlorophyll: Partial synthesis of a putative intermediary catabolite. Preliminary communication
Authors: Kräutler Bernhard , Mühlecker Walter , Anderl Maximilian , Gerlach Benjamin
Published: December 2004

The partial synthesis of 10,22‐dihydro‐4,5‐dioxo‐4,5‐secopheophorbide a (1) from pheophorbide a methyl ester (2) is described. A regioselective, photooxygenolytic reaction of (pheophorbidato a methyl ester)cadmium(II)(3) provides the entry to the crucial 4,5‐secoporphinoid structure in form of the (10,22‐dihydro‐4,5‐dioxo‐4,5‐seco‐pheophorbidato a methyl ester)cadmium(II) (4). The hydride reduction of this 4,5‐dioxo‐4,5‐secophytoporphyrin ester occurs selectively at the ‘eastern’ meso‐position to lead (after demetallation) to 10,22‐dihydro‐4,5‐dioxo‐4,5‐secopheophorbide a methyl ester (5). This oxobilin‐carbaldehyde has the structure assigned earlier to an ester of an isolation form of the red pigment(s) from Chlorella protothecoides. Hydrolysis of the propanoate ester function of 5, selectively catalyzed by pig liver esterase, then yields the title compound 1. The red tetrapyrrole 1 may represent an intermediary chlorophyll catabolite in degreening plants.
Synthesis of Benzo[a]heptalene
Authors: Guspanová Jana , Knecht Roger , Laganà Markus , Weymuth Christophe , Hansen Hans‐Jürgen
Published: December 2004

Benzo[a]heptalene has been synthesized by two different approaches. The first one follows a pathway to hexahydrobenzo[a]heptalenone 19a that has been already described by Wenkert and Kim(Scheme). Indeed, 19a was obtained in a mixture with its double‐bond‐shifted isomer 19b. Reduction of this mixture to the corresponding secondary alcohols 26a/26b and elimination of H2O lead to a mixture of the tetrahydrobenzo[a]heptalenes 23a‐d (Scheme7 and 8). Reaction of 23a‐d with 2 equiv. of triphenylmethylium tetrafluoroborate in boiling CHCl3, followed by treatment with Me3N in CH2Cl2, generated directly 2, unfortunately in a mixture with Ph3CH that could not be separated from 2 (Scheme 10 and 11). The second approach via dimethyl benzo[a]heptalene‐6,7‐dicarboxylate (30) (Scheme 12) that was gradually transformed into the corresponding carbaldehydes 37 and 43 (Scheme 14) both of which, on treatment with the Wilkinson catalyst [RhCl(PPh3)3] at 130° in toluene, smoothly decarbonylated, finally gave pure 2 as an unstable orange, viscous oil. UV/VIS, NMR, and mass spectra of 2 are discussed in detail (cf. Chapt.3).
Solid‐Phase Synthesis of a Sialyl‐Tn‐Glycoundecapeptide of the MUC1 Repeating Unit
Authors: Liebe Beate , Kunz Horst
Published: December 2004

The synthesis of glycopeptides carrying tumour‐associated antigens is of interest for cancer diagnosis and treatment. Here, a very efficient route lo disaccharide threonine building block 8 is presented which allows the introduction of the sialyl‐Tn antigen into a peptide. The syntheses of the undecapeptide and the sialyl‐Tn‐containing glycoundecapeptide, which are a part of the repeating unit of MUC1, were performed by solid‐phase synthesis with an allylic anchor cleavable under neutral conditions. After detachment from the resin, the peptide and the glycopeptide arc completely deprotected giving the target compounds 13 and 15, respectively.
Synthesis and Properties of First and Second Generation Chiral Dendrimers with Triply Branched Units: A Spectacular Case of Diastereoselectivity
Authors: Murer Peter K. , Lapierre Jean‐Marc , Greiveldinger Guy , Seebach Dieter
Published: December 2004

Chiral triols (which may be considered as derivatives of tris(hydroxymethyl)methane), without (3‐5) and with aliphatic (6) or aromatic (7) elongating units, and the 1st‐ and 2nd‐generation benzylic branched bromides, 17, 18, 23, 24, 29, and 30 are subjected to Williamson etherification conditions (NaH in THF). This gave the first ‘fully chiral’ dendrimers, with triple branching and with a stereogenic center at each and every branching point (including the central building block: see 33‐42, 44, and 46‐49). Higher than 2nd‐generation dendrimers of this type could not be prepared. Certain combinations of diastereoisomeric 2nd‐generation branched bromides, 23, 24, 29, and 30, and enantiomeric center‐piece triols, 3 and 4, would smoothly react to give the desired dendrimers (e.g., 44, and 46‐49) and others would not, with the reactions stopping at the dendritic alcohols containing only two branches (e.g., 45, and 50‐53; see Schemes 4 and 5). Considering the distance at which the intermediate diastereoisomeric ‘doubly coupled’ dendritic alcohols differ in their configuration, this diastereodifferentiation or molecular recognition phenomenon (discovered by trying to prepare only 8 out of 239 possible diastereoisomers!) is a most surprising result. All compounds were fully characterized, and the 2nd‐generation dendrimers, e.g., 38, 40, and 47 with and without elongation were shown to be monodisperse and without defects, by MALDI‐TOF mass spectroscopy (cf. Fig. 4). A simple, unambiguous nomenclature for identification of the novel dendritic compounds is proposed and applied in the Exper. Part.
Conformation and Dynamics of (−)‐β‐Caryophyllene
Authors: Hübner Matthias , Rissom Beate , Fitjer Lutz
Published: December 2004

(−)‐β‐Caryophyllene (1) adopts three conformations in solution: αα(48%), βα(28%), and ββ(24%). The conformations were identified by an analysis of the 13C‐ and 1H‐NMR spectra at −87.2 and −153.8° in connection with APT, HETCOR, and COSY spectra, and subsequent NOESY experiments. The activation parameters of the conversion αα → βα were determined from a bandshape analysis of exchange‐broadened 13C‐NMR spectra of 8‐[methylene‐13C]‐1 to give ΔH≠ = 5.9 ± 0.3 kcal/mol, ΔS = −8.1 ± 1.8 cal/mol. · K. and ΔG = −8.3 ± 0.8 kcal/mol. The observed population ratio of the different conformers is best described by MM3.
Dendritic styryl TADDOLs as novel polymer cross‐linkers: First application in an enantioselective Et2Zn addition mediated by a polymer‐incorporated titanate. Preliminary communication
Authors: Rheiner P. Beat , Sellner Holger , Seebach Dieter
Published: December 2004

TADDOLs (α,α,α′,α′,‐tetraaryl‐1,3‐dioxolane‐4,5‐dimethanols) with dendritic branches attached to the aryl groups and with 8 or 16 peripheral styryl double bonds have been synthesized (4 and 5). With these compounds, dendritic molecules were employed for the first time as cross‐linkers in a polymerization. The resulting polystyrene was loaded with titanate (Ti(OCHMe2)4) to generate polymer beads incorporating Ti‐TADDOLate centers (Figs. 1 and 2) for enantioselective catalysis (Et2Zn addition to PhCHO). Compared with conventionally polymer‐attached, insoluble Ti‐TADDOLates (cf. 3), the new materials have a much higher catalytic activity, rather close to that of soluble analogs (Fig. 3).
Novel leptomycins from a streptomyces strain A92‐308902: Inhibitors of the Nucleo‐cytoplasmic translocation of the HIV‐1 regulatory protein Rev
Authors: Wang Ying , Ponelle Monique , Sanglier Jean‐Jacques , Wolff Barbara
Published: December 2004

As one of the regulatory gene products in the HIV‐1 genome, Rev protein must be translocated from the nucleus to the cytoplasm to exert its function. Therefore, inhibition of Rev protein translocation could be a useful target for HIV therapy. An extract from the Streptomyces strain A92‐308902 with very potent inhibitory activity was found in the course of a high throughput screening with a Rev translocation assay (RTA). Bioassay‐guided fractionation with gel filtration, normal‐phase and reversed‐phase chromatography yielded six RTA‐active metabolites belonging to the leptomycin family, the known leptomycin A (1), leptomycin B (2), kazusamycin B (3), and kazusamycin A (4). and the hitherto unknown dilactonmycin (5) and delactonmycin (6), together with an inactive cyclic hexadepsipeptide L‐156,620 (7). The structures were established mainly by spectroscopic methods (UV, FT‐IR, FAB‐MS, 1H‐NMR, 13C‐NMR(JMOD), DQ‐COSY, ROESY, HSQC, and HMBC). The configuration of all CC bonds of 1–6 was unambiguously established by analysis of coupling constants and ROESY spectra. All isolated leptomycins 1–6 inhibit Rev translocation at nanomolar concentrations. Six derivatives (2a–c and 4a–c) of leptomycin B (2) and kazusamycin A (4) were also prepared and tested in the RTA for preliminary investigations on structure‐activity relationships.
Structure and reactivity of a sulfoximine‐stabilized chiral dilithiocarbanion
Authors: Müller Jürgen F. K. , Neuburger Markus , Zehnder Margareta
Published: December 2004

The synthesis and X‐ray analysis of a racemic dilithiated S‐ethyl‐N‐methyl‐S‐phenylsulfoximine cluster 2 with N,N,N′,N′‐tetramethylethane‐1,2‐diamine (TMEDA) as coordinating solvent is presented. The lithium complex 2 consists of a mixed tetrameric mono‐ and dilithio salt. Unexpectedly, a separation of the enantiomers in mono‐and dilithiated antipodes with respect to the chirality center on the S‐atom is observed. Dilithiation of S‐ethyl‐N‐methyl‐S‐phenylsulfoximine (1) affords a chiral dinucleophile which undergoes highly regie‐ and stereoselective alkylation reactions with bis‐electrophiles.
Synthesis and structure of (carboxymethyl)‐functionalized cyclobuta‐fused uracil dimers
Authors: Carell Thomas , Epple Robert , Gramlich Volker
Published: December 2004

Herein, we report a convenient method for the preparation of four benzyl‐ester‐protected, (carboxymethyl)‐functionalized cyclobuta‐fused uracil dimers 1–4, including the desired cis‐cisoid‐cis,syn‐ configured isomer 1, a compound which is suitable for the preparation of catalytic antibodies, synthetic receptors, and model compounds, required for the investigation of the DNA‐lesion, recognition step and DNA‐repair mechanisms. A comprehensive structure determination of each isomer by 1H‐NMR, and in the case of the cis‐cisoid‐cis,syn‐ and the cis‐traftsoid‐cis,Syn‐dimers by X‐ray crystal‐structure analysis, is also provided.
Ein erstes Beispiel eines porphyrinoiden Fulvalens: Synthese, Struktur, ESR‐ und elektrochemische Untersuchungen
Authors: Markl Gottfried , Hafner Markus , Kreitmeier Peter , Stadler Christian , Daub Jörg , Nöth Heinrich , Schmidt Martin , Gescheidt Georg
Published: December 2004

A First Example of a Porphyrinoid Fulvalene: Synthesis, Structure, ESR and Electrochemical Investigations

The macrocyclic tetraepoxy‐1H‐[21]annulen‐1‐one 4 can by synthesized by the cyclizing Wittig reaction of 5,5′‐carbonylbis[furan‐2‐carboxaldehyde] (11) and the bisphosphonium salt 12, obtained from 2,2′‐bifuran‐5,5′‐dicarboxaldehyde (13). According to an X‐ray structure analysis, the annulenone 4 is not planar in the crystal; the 1H‐NMR spectra of 4 reveal an averaged planarity with respect to the NMR timescale. The McMurry reaction of 4 yields fulvalene 3 in 43% yield as the most expanded fulvalene hithertoo known. The X‐ray structure analyses of 3 surprising establishes a ‘syn’‐orientation of the two rings with respect to the central CC bond, thus forming a basket‐like molecule. The 1H‐NMR spectrum confirms the averaged planarity of both macrocycles in 3. CV and spectroelectrochemical measurements of 3 suggest a reversible two‐electron reduction producing dianion 15 with two aromatic, anionic 5a,15a‐didehydro‐10H‐21,22,23,24‐tetraoxa‐5a,15a‐dihomocorrole (= tetraoxa[22]porphyrin(2.1.2.0)) ring systems containing 22π electrons each. The formation of 15 can also be achieved chemically by reaction of 3 with metallic potassium. The dication 16 of 3 may be antiaromatic, but the exact electronic structure is dubious. ESR and ENDOR investigations on the radical cation and the radical anion of 3 indicate that the free electron is delocalized in the entire molecule.
Enantioselective 1,4‐Addition of Aliphatic Grignard Reagents to Enones Catalyzed by Readily Available Copper(I) thiolates derived from TADDOL. Preliminary communication
Authors: Seebach Dieter , Jaeschke Georg , Pichota Arkadius , Audergon Laurent
Published: December 2004

Two simple thiols derived from the parent TADDOL, α,α,α′,α′ tetraphenyl‐2,2‐dimethyl‐1,3‐clioxolan‐4,5‐dimethanol, are used to prepare Cu1 complexes C and D to catalyze (0.05 equiv.) 1,4‐additions of Grignard reagents RMgCl to cyclic enones with enantioselectivities which are comparable to or better than previously reported (enantiomer ratios up to 92:8).
Preparation and Absolute Configuration of (−)‐(E)‐α‐trans‐Bergamotenone
Authors: Chapuis Christian , Barthe Michel , Muller Bernard L. , Schulte‐Elte Karl H.
Published: December 2004

The synthesis, absolute configuration, and olfactive evaluation of (−)‐(E)‐α‐trans‐bergamotenone (= (−)‐(1′S,6′R,E)‐5‐(2′,6′‐dimethylbicyclo[3.1.1]hept‐2′‐en‐6′‐yl)pent‐3‐en‐2‐one; (−)‐1), as well as its homologue (−)‐19 are reperted. The previously arbitrarily attributed absolute configuration of 1 and of (−)‐α‐trans‐bergamotene (= (−)‐(1 S,6R)‐2,6‐dimethyl‐6‐(4‐methylpent‐3‐enyl)bicyclo[3.1. 1]hept‐2‐ene; (−)‐2), together with those of the structurally related aldehydes (−)‐3a,b and alcohols (−)‐4a,b, have been rigorously assigned.
Asymmetric Synthesis of (S)‐5,5,5,5′,5′,5′,5′‐Hexafluoroleucine
Authors: Zhang Cong , Ludin Christian , Eberle Marcel K. , Stoeckli‐Evans Helen , Keese Reinhart
Published: December 2004

(S)‐5,5,5,5′,5′,5′‐Hexafluoroleucine ((S)‐13) of 81 % ee is prepared from hexafluoroacetone (l) and ethyl bromopyruvate (= ethyl 2‐oxopropanoate) in 7 steps with an overall yield of 18% (Schemes 1 and 2). Key step in this sequence is the highly enantioselective reduction of the carbonyl group in α‐keto ester 4 either by bakers' yeast (91 % ee) or by ‘catecholborane’ 6 utilizing an oxazaborolidine catalyst, yielding hydroxy ester (R)‐5 with 99% ee. The absolute configuration was determined by X‐ray analysis of the HCl adduct (S,R)‐9b of (2S)‐N‐[(R)‐ l‐phenylethyl]‐5,5,5,5′,5′,5′‐hexafluoroleucine ethyl ester.
7‐Deazapurine Oligodeoxyribonucleotides: The effects of 7‐deaza‐8‐methylguanine on dna structure and stability
Authors: Seela Frank , Chen Yaoming , Mittelbach Cathrin
Published: December 2004

Oligodeoxyribonucleotides containing 7‐deaza‐2′‐deoxy‐8‐methylguanosine (m8c7Gd; 2b) were prepared. For this purpose, the phosphonate 3a and the phosphoramidite 3b were synthesized and employed in solidphase oligodeoxyribonucleotide synthesis. The structures and the thermodynamic data of duplex formation of oligodeoxyribonucleotides containing 2b were investigated by temperature‐dependent CD and UV spectra and compared with those containing 7‐deaza‐2′‐deoxy‐7‐methylguanosine (m7c7Gd) or 7‐deaza‐2′‐deoxy‐guanosine (c7Gd; 2a). In general, compound 2b reduces the duplex stability. In case of the sequence d(m8c7G‐C)4 (18), the B → Z transition was facilitated by the incorporation of 2b. Moreover, a single 7‐deaza‐8‐methylguanine residue present in an oligodeoxyribonucleotide tract of guanine residues destabilizes the dG quadruplex significantly. This destabilization is more pronounced than in the case of 7‐deazaguanine or 7‐deaza‐7‐methyl‐guanine.
Synthesis and Study of New β‐Cyclodextrin ‘Dimers’ Having a Metal Coordination Center and carboxamide or urea linkers
Authors: Sallas Florence , Marsura Alain , Petot Virginie , Pintér István , Kovács Joseph , Jicsinszky Laszlo
Published: December 2004

The synthesis of new ‘bridged’ β‐cyclodextrin (β‐CD) ‘dimers’ 7–12 was successfully achieved by two one‐pot reactions from β‐CD (3) and 6A‐azido‐6A‐deoxy‐β‐CD (4). The ‘phosphine imine’ reaction was shown to be a superior approach compared to the Mitsunobu reaction as coupling strategy for the preparation of these ‘dimers’. NMR Data, along with molecular‐modelling calculations, suggest a ‘helical‐like’ arrangement for the phenanthroline‐diyl‐linked ‘dimer’ derivative 9. Complexation properties of 9 were established by UV‐VIS‐spectrophotometric titration toward four metals. Among them CuII or EuIII ions were complexed selectively by 9, but no complexation occurred with LaIII and ZnII. In addition a specific and interesting esterase activity toward the phosphodiester bond of bis(4‐nitrophenyl) phosphate anion was found in the case of the CuII complex of 9.
A Novel Solution‐ and Solid‐Phase Approach to 2,4,5‐tri‐ and 2,4,5,6‐tetrasubstituted pyrimidines and their conversion into condensed heterocycles
Authors: Masquelin Thierry , Sprenger Daniel , Baer Roman , Gerber Fernand , Mercadal Yves
Published: December 2004

A novel general synthesis of 2,4,5‐tri‐ and 2,4,5,6‐tetrasubstituted pyrimidines 5a–d and 7a, e, f, g by condensation of thiouronium salts of type 3 with (ethoxymethylidene)malononitrile (4) and [bis(methylthio)methylidene]malononitrile (6), respectively, was first established in solution (Scheme 1) and successfully transferred onto solid support by using the polymer‐bound thiouronium salt 11 (Scheme 3). Further investigations were directed toward a multidirectional cleavage procedure of the 2‐(alkylsulfinyl) intermediates, obtained from the 2‐(alkylthio)pyrimidines 7a (Scheme 2) or 12 and 14 (Schemes 3 and 4), with different nucleophiles to form highly substituted pyrimidines. In addition, fused‐heterocycle derivatives 22a‐‐h, 24a–c, and 26a–e were generated in good‐to‐excellent yields by condensation of 7a, e, h with versatile isocyanates and isothiocyanates, with subsequent alkylation (Scheme 5).
Orbital‐Symmetry Effects in Bimolecular Electron‐Transfer Reactions: Back Electron Transfer
Authors: Haselbach Edwin , Pilloud Denis , Suppan Paul
Published: December 2004

Previous work has indicated orbital‐symmetry effects upon forward electron transfer inbimolecular systems, with magnitude similar to that encountered in rigidmonomolecular systems. The present work, which employs back electron transfer, supports and extends these earlier findings.
New Axially Chiral Bis(dihydrooxazoles) as Ligands in Stereoselective Transition‐Metal Catalysis
Authors: Rippert Andreas Johannes
Published: December 2004

The new, axially chiral bis(4,5‐dihydrooxazoles) 4 have been synthesized in a straightforward manner, starting from the substituted, racemic 1,1′‐biphenyl‐2,2′‐dicarboxylic acids 1 and optically active amino alcohols 2. The adducts were resolved by medium‐performance liquid chromatography (MPLC; see Scheme 1). Formation of Cu1 complexes of 4 was followed by 1H‐NMR spectroscopy. The catalytic behavior of these complexes has been investigated by asymmetric cyclopropanation of styrene with ethyl diazoacetate. Beside the influence of steric factors, a significant electronic effect on asymmetric induction could also be observed (see Scheme 2 and Table).
Selective Derivatization of the Ionophore X‐206 at C(22) Maintaining Potassium Binding
Authors: O'Sullivan Anthony C. , Struber Fritz
Published: December 2004

The insecticidal polyether antibiotic X‐206 (1) complexes potassium ions using nearly all of its O‐atoms either for binding to the metal ion or for participation in a H‐bonding network which helps to hold X‐206 in the ionophoric tertiary structure. The group OHC(22) is not involved in these processes. It was supposed that derivatization of this group would not affect the ionophoric properties and would produce insecticidally active compounds. The chemistry leading to selective modification of OHC(22) via the intermediate 6 was developed. The potassium‐binding properties and insecticidal activities of the MeCOOC(22) and MeOC(22) compounds 3 and 11, respectively, confirmed that derivatization of the peripheral OHC(22) was a valid strategy for the synthesis of biologically active compounds.
Cooperative Interactions of the Catalytic Nucleophile and the Catalytic Acid in the Inhibition of β‐Glycosidases. Calculations and their validation by comparative kinetic and structural studies of the inhibition of glycogen phosphorylase b
Authors: Heightman Tom D. , Vasella Andrea , Tsitsanou Katerina E. , Zographos Spyros E. , Skamnaki Vicky T. , Oikonomakos Nikos G.
Published: December 2004

The difference between the strong inhibition of retaining β‐glucosidases by the tetrazole 1 and the weak inhibition by the triazole 3 has been explained by the protonation by the enzymic catalytic acid of N(3) of 1, replaced by CH in 3. One also expects a contribution to the inhibition from the charge‐dipole interaction between the enzymic catalytic nucleophile and the azole ring. The extent of this contribution was estimated from the calculated, distance‐dependent heats of formation of the acetate‐azole complexes. The calculations were validated by comparison of the charge‐dipole interaction between phosphate and the inhibitors 1 and 3 in the glycogen phosphorylase b (GPb)‐azole‐phosphate complexes, as derived from differences in the Ki values for 1 and 3, while the structural invariance of the complexes was demonstrated by X‐ray analysis. The difference between the charge‐dipole interactions of (dihydrogen) phosphate and 1 or 3 as derived from Δ Ki is 1.1 kcal mol−1, while the calculated difference is 1.3 kcal mol−1. The calculated difference for the interaction of 1 or 3 with acetate, representing the catalytic nucleophile in β‐glycosidases, is 2.0 kcal mol−1, while the differences of the binding energies as derived from the Ki values for the inhibition by 1 or 3 of different β‐glycosidases range from 2.4 to 5.3 5 kcal mol−1. The calculated difference for 1 and the imidazole 6 is 2.5 kcal mol−1 in favour of 1, whereas the Ki‐derived difference is 3.7 kcal mol−1 in favour of 6, equal to the calculated difference between 1 and the protonated imidazole 6. Thus, protonation by the catalytic acid and the charge‐dipole interaction with the catalytic nucleophile contribute cooperatively to the binding of inhibitors possessing a trigonal anomeric centre bonded to a heteroatom.
γ‐Peptides Forming More Stable Secondary Structures than α‐Peptides: Synthesis and helical NMR‐solution structure of the γ‐hexapeptide analog of H‐(Val‐Ala‐Leu)2‐OH
Authors: Hintermann Tobias , Gademann Karl , Jaun Bernhard , Seebach Dieter
Published: December 2004

For a comparison with the corresponding α‐ and β‐hexapeptides H‐(Val‐Ala‐Leu)2‐OH (A) and H‐(β‐HVal‐β‐HAla‐β‐HLeu)2‐OH (B), we have now prepared the corresponding γ‐hexapeptide 1 built from the homochirally similar (S)‐4‐aminobutanoic acid, (R)‐4‐amino‐5‐methylhexanoic acid, and (R)‐4‐amino‐6‐methylheptanoic acid. The precursors were prepared either by double Arndt‐Eistert homologation of the protected amino acids Boc‐Val‐OH, Boc‐Ala‐OH, and Boc‐Leu‐OH (Schemes 1 and 2), or by the superior route involving olefination/hydrogenation of the corresponding aldehydes (Boc‐valinal, Boc‐alaninal, and Boc‐leucinal; Scheme 3). Conventional peptide‐coupling methodology (EDC/HOBt) furnished the γ‐hexapeptide 1 (through the intermediate γ‐di‐ and γ‐tripeptide derivatives 9–11). Analysis of NMR measurements in (D5)pyridine and CD3OH solution (COSY, TOCSY, HSQC, HMBC, ROESY) reveals that the γ‐hexapeptide 1 adopts a right‐handed helical structure ((P)‐2.61 helix of ca. 5‐Å pitch, containing 14‐membered H‐bonded rings) which is to be compared with the left‐handed helix of the corresponding β‐peptide B ((M)‐31 helix of 5‐Å pitch, 14‐membered H‐bonded rings) and with the familiar right‐handed, so‐called α‐helix of α‐peptides ((P)‐3.61 helix of 5.4‐Å pitch, 13‐membered rings). Like the helix sense, the helix dipole reverses when going from α‐, (N + → C) to β‐(C + → N) to γ‐peptides (N + → C). The surprising difference between the natural α‐, and the analogous β‐ and γ‐peptides is that the helix stability increases upon homologation of the residues.
Sulfur‐Containing Heterocycles Derived by Reaction of ω‐Keto Amides with Lawesson's Reagent
Authors: Nishio Takehiko
Published: December 2004

The reaction of ω‐keto amides with Lawesson's reagent (LR: 2,4‐bis(4‐methoxyphenyl)‐1,3,2,4‐dithiadiphosphetane 2,4‐disulfide) is described. Treatment of 3‐keto amides (2‐acylacetamides) 1 with LR gave the corresponding 3‐keto thioamides 2, along with 1,2‐dithiole‐3‐thiones 3. Treatment of 4‐keto amides, 3‐acyl propionamides 5, with LR yielded five‐membered heterocycles, pyrroles 6 and/or 2‐aminothiophenes 7. 5‐Keto amides, 3‐benzoyl butyramides 8, reacted with LR to give dihydrothiopyran‐2‐thione 9 as the sole product, but in low yield. 2‐Acylbenzamides 10 also reacted with LR to afford 3‐mercaptoisoindolin‐2‐ones 11 or dihydroisobenzothiophene‐1‐thiones 12.
On the Origin of Asymmetric Induction of the Palladium‐Catalyzed Allylic Substitution Reaction with Chiral 4,4‐Disubstituted 4,5‐Dihydro‐2‐(phosphinoaryl)oxazole Ligands
Authors: Schaffner Silvia , Müller Jürgen F. K. , Neuburger Markus , Zehnder Margareta
Published: December 2004

The X‐ray analyses of (η3‐allyl){4‐benzyl‐2‐[2‐(diphenylphosphino‐κP)phenyl]‐4,5‐dihydro‐4‐4‐methyloxazole‐κN}palladium(II) hexafluorophosphate (5) and the analogous [Pd(η3‐1,3‐diphenylallyl)] complex 6 are presented. A comparison with the (η3‐allyl)‐ and (η‐1,3‐diphenylallyl)palladium complexes 2 and 3, respectively, containing the 4‐monosubstituted 4,5‐dihydro‐2‐(phosphinoaryl)oxazole ligand 1a reveals important structural differences (Fig. 3). 1H‐NMR Spectroscopic investigation confirm that the 4,4‐disubstituted 4,5‐dihydro‐2‐(phosphinoaryl)oxazole ligand 4 of 5 and 6 shows the same conformation in solution as in the solid state (Table 2). The application of ligand (S)‐4 in the Pd‐catalyzed allylic substitution demonstrates a configurational relationship between the orientation of the allyl ligand in the intermediate (cf. complex 6) and the absolute configuration of the allylic‐substitution product (Table 3).
Partial Synthesis and Characterization of Capsokarpoxanthins and 3,6‐Epoxcapsanthins
Authors: Deli József , Molnár Péter , Matus Zoltán , Tóth Gyula , Steck Andrea , Pfander Hanspeter
Published: December 2004

The acid‐catalyzed hydrolysis of (3S,5R,6S,3′S,5′R)‐5,6‐epoxycapsanthin (5) led to (3S,5R,6R,3′S,5′R)‐(7) and (3S,5R,6S,3′S,5′R)‐capsokarpoxanthin (8). In addition, (3S,5R,8R,3′S,5′R)‐ (9), (3S,5R,8S,3′S,5′R)‐capsochrome (10), and (3S,5R,6R,3′S,5′R)‐3,6‐epoxycapsanthin (6) afforded (3S,5S,6R,3′S,5′R)‐capsokarpoxanthin (12) (3S,5S,8S,3′S,5′R)‐ (13) and (3S,5S,8R,3′S,5′S)‐capsochrome (14) as well as (3S,5S,6R,3′S,5′R)‐3,6‐epoxyepicapsanthin (15). Compounds 5–15 were isolated in crystalline form and characterized by their UV/VIS, CD, 1H‐ and 13C‐NMR, and mass spectra.
Synthesis and Structure Elucidation of a New Potent Sandalwood‐Oil Substitute
Authors: Bajgrowicz Jerzy A. , Frank Iris , Fráter Georg , Hennig Michael
Published: December 2004

New derivatives of campholenaldehyde (= 2‐(2,2,3‐trimethylcyclopent‐3‐enyl)ethanal bearing two cyclopropane moieties were synthesized, and the structure of the stereoisomer responsible for its exceptionally strong, diffusive, and natural sandalwood‐oil scent, ((1S,2S)‐1‐methyl‐2‐{[1S,3R,5R)‐1,2,2‐trimethylbicyclo[3.1.0]hex‐3‐yl]methyl}cyclopropyl)methanol (13a), was elucidated.
A Synthetic Receptor for β,β‐Carotene: Towards an enzyme mimic for central cleavage
Authors: French Richard R. , Wirz Jakob , Woggon Wolf‐Dietrich
Published: December 2004

We report on the synthesis of a receptor 4 for β,β‐carotene (1), and on the binding interaction between the two which yields inclusion complex 5. The cyclodextrin ‘dimer’ 4 was obtained via condensation of the corresponding 4,4′‐(porphyrin‐5,15‐diyl)bis phenol 8 with 6A‐deoxy‐6A‐iodo‐β‐cyclodextrin (6) in the presence of Cs2CO3. Fluorescence studies of the binding interaction between ‘dimer’ 4 and β,β‐carotene (1) gave a binding constant Ka of (2.4 ± 0.1) · 106 M−1.
Blood compatibility of methyl, methyl vinyl, methyl phenyl, and trifluoropropylmethylvinyl silicone rubber without silica fillers in the spiral‐coiled membrane lung
Authors: Kolobow T. , Tomlinson T. A. , Pierce J. E.
Published: December 2004

Spiral‐coiled membrane lungs of 0.6 m2 surface area were fabricated from silicone rubber membranes coated with four types of commercially available pure‐gum polysiloxane rubber: 1) polytrifluoropropylmethylvinylsiloxane, 2) polymethylphenylsioxane, 3) polymethylvinylsiloxane, and 4) polydimethylsiloxane.

Membrane lungs were tested in an arteriovenous shunt without added heparin after bypass was begun. All groups except group 4 had major rise in resistance to blood flow or clotting in over 33% of the membrane lungs studied, after 6 hr of bypass. Membrane lungs with polydimethylsiloxane (group 4) had no rise in resistance to blood flow during 24 hr of bypass and had the least amount of changes in blood platelet count.