bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer‐ and Dendrimer‐Bound Ti‐TADDOLates in Catalytic (and Stoichiometric) Enantioselective Reactions: Are pentacoordinate cationic Ti complexes the catalytically active species?
Authors: Seebach Dieter , Marti Roger E. , Hintermann Tobias 
Published: December 2004

Abstractα,α,α′,α′‐Tetraaryl‐1,3‐dioxolane‐4,5‐dimethanols (TADDOLs), containing styryl groups either at C(2) of the heterocyclic ring or in the α‐position, were prepared in the usual way (18–22, 24, 25). These compounds were copolymerized with styrene and divinylbenzene in a suspension, yielding polymers (33–40, Scheme 3) as beads with a rather uniform particle‐size distribution (150–45 μm), swellable in common organic solvents. HOCH2‐ and BrCH2‐substituted TADDOLs were also prepared and used for attachement to Merrifield resin or to dendritic molecules (23, 26–32). The TADDOL moieties in these materials are accessible to form Ti (and Al) complexes (Scheme 4) which can be used as polymer‐ or dendrimer‐bound reagents (stoichiometric) or Lewis acids (catalytic). The reactions studied with these new chiral auxiliaries are: enantioselective nucleophilic additions to aldehydes (of R2Zn and RTi(OCHMe2)3; Scheme 5, Table 1) and to ketones (of LiAlH4, Table 2); enantioselective ring opening of meso‐anhydrides (Scheme 6); [4+2] and [3+2] cycloadditions of 3‐crotonyl‐1,3‐oxazolidin‐2‐one to cyclopentadiene and to (Z)‐N‐benzylidenephenylamine N‐oxide ( → 48, 49, Scheme 7, Tables 3, 4, and Fig. 5). The enantioselectivities reached with most of the polymer‐bound or dendritic TADDOL ligands were comparable or identical to those observed with the soluble analogs. The activity of the polymer‐bound Lewis acids was only slightly reduced as compared with that encountered under homogeneous conditions. Multiple use of the beads (up to 10 times), without decreased performance, has been demonstrated (Figs. 3 and 4). The poorer selectivity in the Diels‐Alder reaction (Scheme 7a), induced by the polymer‐bound Cl2Ti‐TADDOLate as compared to the soluble one, is taken as an opportunity to discuss the mechanism of this Lewis‐acid catalysis, and to propose a cationic, trigonal‐bipyramidal complex as the catalytically active species (Fig. 6). It is suggested that similar cations may be involved in other Ti‐TADDOLate‐mediated reactions as well.
The First Asymmetric Intramolecular Stetter Reaction. Preliminary Communication
Authors: Enders Dieter , Breuer Klaus , Runsink Jan , Teles J. Henrique 
Published: December 2004

AbstractThe first asymmetric intramolecular Stetter reaction is reported, using the chiral triazolium salt 1 as catalyst. Starting from the easily accessible 4‐(2‐formylphenoxy)but‐2‐enoates 2, this protocol opens up an enantioselective pathway to the benzo‐annulated pyran‐4‐ones (chroman‐4‐ones) 3a–h with good yields and enantiomeric excesses of up to 74%.
Hydrolytical Cleavage of TAR‐RNA, the trans‐Activation Responsive Region of HIV‐1, by a Bis(guanidinium) Catalyst Attached to Arginine
Authors: Kurz Kristina , Göbel Michael W. 
Published: December 2004

AbstractGuanidinium compounds imitating the bis(arginine) structural motif of staphylococcal nuclease (e.g. 3) are known to be powerful catalysts for phosphoryl transfer reactions in dipolar aprotic solvents. Compound 3 also accelerates the hydrolysis of RNA (H2O, pH 7). However, due to diminished substrate affinity in H2O, the rate effects are less pronounced in aqueous than in aprotic solution. To test if a synthetic ribonuclease may be derived from the bis(guanidinium) moiety of 3 by the addition of RNA‐binding substructures, the TAR sequence of HIV‐1 was chosen as a target. The arginine residue of compound 4 serves as an extremely simplified mimic of tat, a protein responsible for boosting the viral transcription by complex formation with TAR. Here, we present the synthesis of 4 and its ability to bind and to cleave efficiently the truncated TAR sequence 1. In addition, the synthesis of an acridine arginine conjugate, 19, is reported in preliminary form. Compound 19 associates with 1 and completely blocks the cleavage induced by 4.
Electrospray‐Ionization Mass Spectrometry. Part III. Acid‐Catalyzed Isomerization of N,N′‐Bis[(E)‐3‐(4‐hydroxyphenyl)prop‐2‐enoyl]spermidines by the Zip Reaction
Authors: Bigler Laurent , Schnider Christian F. , Hu Wenqing , Hesse Manfred 
Published: December 2004

AbstractThe electrospray tandem mass spectra (ESI‐MS/MS) of the three N,N′‐bis[(E)‐3‐(4‐hydroxyphenyl)prop‐2‐enoyl]spermidines 1–3 displayed the same fragment‐ion signals. These isomers could not be differentiated by ESI‐MS/MS, since their fragmentation patterns are similar. (E,E)‐N‐(3‐[15N]Aminopropyl)‐3,3′‐bis(4‐ hydroxyphenyl)‐N,N′‐(butane‐1,4‐diyl)bis[prop‐2‐enamide] ([15N(1)])‐(1) was synthesized in order to get further information about the fragmentation mechanisms. The comparison of the ESI‐MS/MS of 1 and [15N(1)]‐1 revealed a transamidation, the Zip reaction, under mass‐spectral conditions of the [1 + H]+ ions. Because of this reaction, the three isomers 1–3 could not be distinguished.
Synthesis of Fused Triazoles as Probes for the Active Site of Retaining β‐Glycosidases: From Which Direction Is the Glycoside Protonated?
Authors: Heightman Tom D. , Locatelli Monica , Vasella Andrea 
Published: December 2004

AbstractThe structure of the β‐glycosidase inhibitors 1–7 and 10–13 suggests that protonation of O–C(1) (the glycosidic O‐center) of the substrate by a carboxy group of the retaining β‐glycosidases does not occur in the plane perpendicular to the ring of the glycon (β‐side; ‘from the top’), but in the plane of the ring (‘from the side’). The triazoles 17 and 18 have been prepared in six steps from the L‐xylofuranose 21. They possess a CH group instead of the N‐center of the related tetrazoles 4 and 5, corresponding to the glycosidic O‐atom, and a very similar structure, both in solution and in the solid state. Unlike the tetrazoles, however, which are good‐to‐medium inhibitors of retaining β‐glycosidases, the triazoles do not inhibit the β‐glycosidases from sweet almonds, snail, and bovine liver, and only slightly inhibit the β‐glucosidase from Caldocellum saccharolyticum. This is in keeping with the proposed direction of protonation in the plane of the saccharide ring and with modelling studies, docking 4 into the active site of the white clover cyanogenic β‐glucosidase and 6 into the E. coli β‐galactosidase and the Lactococcus lactis 6‐phospho‐β‐galactosidase.
Double‐Bond Shifts in [4n]Annulenes as a New Principle for Molecular Switches: First Results with Dimethyl Heptalene‐1,2‐ and ‐4,5‐dicarboxylates
Authors: Briquet Anne Andrée Sophie , Uebelhart Peter , Hansen Hans‐Jürgen 
Published: December 2004

AbstractA new concept for molecular switches, based on thermal or photochemical double‐bond shifts (DBS) in [4n]annulenes such as heptalenes or cyclooctatetraenes, is introduced (cf. Scheme 2). Several heptalene‐1,2‐ and ‐4,5‐dicarboxylates (cf. Scheme 4) with (E)‐styryl and Ph groups at C(5) and C(1), or C(4) and C(2), respectively, have been investigated. Several X‐ray crystal‐structure analyses (cf. Figs. 1–5) showed that the (E)‐styryl group occupies in the crystals an almost perfect s‐trans‐conformation with respect to the CC bond of the (E)‐styryl moiety and the adjacent CC bond of the heptalene core. Supplementary 1H‐NOE measurements showed that the s‐trans‐conformations are also adopted in solution (cf. Schemes 6 and 9). Therefore, the DBS process in heptalenes (cf. Schemes 5 and 8) is always accompanied by a 180° torsion of the (E)‐styryl group with respect to its adjacent CC bond of the heptalene core. The UV/VIS spectra of the heptalene‐1,2‐ and ‐4,5‐dicarboxylates illustrated that it can indeed be differentiated between an ‘off‐state’, which possesses no ‘through‐conjugation’ of the π‐donor substituent and the corresponding MeOCO group and an ‘on‐state’ where this ‘through‐conjugation’ is realized. The ‘through‐conjugation’, i.e., conjugative interaction via the involved s‐cis‐butadiene substructure of the heptalene skeleton, is indicated by a strong enhancement of the intensities of the heptalene absorption bands I and II (cf. Tables 3–6). The most impressive examples are the heptalene‐dicarboxylates 11a, representing the off‐state, and 11b which stands for the on‐state (cf. Fig.8).
Pyranosyl‐RNA (‘p‐RNA’): NMR and Molecular‐Dynamics Study of the Duplex Formed by Self‐pairing of Ribopyranosyl‐(C‐G‐A‐A‐T‐T‐C‐G)
Authors: Schlönvogt Irene , Pitsch Stefan , Lesueur Catherine , Eschenmoser Albert , Jaun Bernhard , Wolf Romain M. 
Published: December 2004

AbstractThe solution structure of the duplex formed by self‐pairing of the p‐RNA octamer β‐D‐ribopyranosyl‐(2′→4′)‐(CGAATTCG) was studied by NMR techniques and, independently, by molecular‐dynamics calculations. The resonances of all non‐exchanging protons, H‐bearing C‐atoms, P‐atoms, and of most NH protons were assigned. Dihedral angle and distance constraints derived from coupling constants and NOESY spectra are consistent with a single dominant conformer and corroborate the main structural features predicted by qualitative conformational analysis. The duplex displays Watson‐Crick pairing with antiparallel strand orientation. The dihedral angles β and ϵ in the phosphodiester linkages differ considerably from the idealized values. Model considerations indicate that these deviations from the idealized model allow better interstrand stacking and lessen unfavorable interactions in the backbone. The average base‐pair axis forms an angle of ca. 40° with the backbone. The resulting interstrand π‐π stacking between either two purines, or a purine and a pyrimidine, but not between two pyrimidines, constitutes a characteristic structural feature of the p‐RNA duplex. A 1000‐ps molecular‐dynamics (MD) calculation with the AMBER force field resulted in an average structure of the same conformation type as derived by NMR. For the backbone torsion angle ϵ, dynamically averaged coupling constants from the MD calculation agree well with the experimental values, but for the angle β, a systematic difference of ca. 25° remains. The two base pairs at the ends of the duplex are calculated to be highly labile, which is consistent with the high exchange rate of the corresponding imino protons found by NMR.
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

AbstractWe 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

AbstractThe 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

AbstractThe 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

AbstractSimple 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

AbstractThree 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractStarting 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.