bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wechselwirkungen in Kristallen, 94. Donator/Akzeptor‐Komplexe von Hydrochinon, Pyren, Perylen und N, N,N′,N′‐Tetramethylbenzidin mit 1,2,4,5‐Tetracyanbenzol oder Tetracyanhydrochinon: Strukturen mit und ohne H‐Brücken‐Netzwerken
Authors: Bock Hans , Seitz Wolfgang , Sievert M. , Kleine M. , Bats Jan W. 
Published: July 2007

Interaction in Crystals, 94. – Donor/Acceptor complexes between Hydroquinone, Pyrene, Perylene, and N, N,N′,N′‐Tetramethylbenzidine with 1,2,4,5‐Tetracyanobenzene or Tetracyanohydroquinone: Structures with and without H Bridge NetworksDonor/acceptor complexes {D ⃛A}∞ can be designed to crystallize in mixed stacks. Due to interplanar ring distances of double π van der Waals radii (340 pm), however, no significant structure changes are observed relative to those of their components. Therefore, it has been attempted to planarize the herringbone patterns of the crystal lattice by additional H bridge networks in order to increase the π interactions between the donor and acceptor rings. The following structural effects are observed: (i) Relative to the complex {perylene ⃛1,2,4,5‐tetracyanobenzene}∞, the planarization of the herringbone pattern by the H bridge network in {pyrene ⃛2,3,5,6‐tetracyanohydroquinone}∞ and {perylene ⃛tetracyanohydroquinone(OH2)2}∞ shortens the layer distance from 345 to 340 pm. Nevertheless, still no significant structural changes due to π electron polarization become apparent. (ii) Despite of identical crystallization conditions from acetic acid solution for both pyrene and perylene inclusion compounds, only the more spacious perylene stretches the H bridges of tetracyanohydroquinone (OH ⃛NC)2 by hydrate water inclusion (OH ⃛OH2 ⃛NC)2 from 265 to 555 pm. (iii) In the complex {hydroquinone ⃛1,2,4,5‐tetracyanobenzene}∞ the phenolic OH substituents generate an extensive H bridge network within the mixed‐staple layers, in which each hydroquinone is surrounded by four tetracyanobenzenes via both strong (OH ⃛NC) and weak (CH ⃛OH) contacts. (iv) In the complex {(tetracyanohydroquinone−)2 ⃛(N, N,N′,N′‐tetramethylbenzidinium(H2+)(OH2)2} an additional proton transfer turns the hydroquinone anion into the donor and the doubly protonated benzidinium dication into the acceptor. – Additional UV/Vis spectroscopic investigations prove long‐wavelength charge transfer bands between 11200 and 19000 cm−1, which are shifted relative to the component absorptions by partly up to 1.5 eV (!) and can be approximated by AM1/CI or PM3/CI calculations. The missing structural changes in the ground state of the complexes {D ⃛A∞} demonstrate therefore, that the electron transfer from donor to acceptor is largely initiated on excitation.
Photochemical Activation of Amino Acids: From the Synthesis of Enantiomerically Pure β,γ‐Unsaturated Amino Acids to Macrocyclic Ring Systems
Authors: Griesbeck Axel G. 
Published: July 2007

AbstractAmino acids whose amino groups are transformed into phthalimido chromophores are versatile substrates for photochemical transformations such as cyclization, isomerization, and β‐cleavage. These processes are initiated by homolytic or mesolytic CH activation and depend on the spin state of the excited substrate. Derivatives of α‐amino acids without strong electron‐donating substituents [Abu, Nva, Val, Leu, Ile, Tle, Phe, Met(SO)] react by initial homolytic CH activation and solely via their first excited singlet states, whereas substrates with strong electron‐donating substituents (Tyr, DOPA, Met, Glu, Asp) react by initial photoinduced electron transfer (PET) followed by mesolytic CH activation and solely via their first excited triplet states. The S‐alkyl cysteine derivatives are the only ones which show competing singlet and triplet state reactivity with pronounced spin‐determined regioselective CH activation. The amino dicarboxylic acids Glu and Asp could be applied as the carboxylates in PET reactions, a strategy which also opened up a new synthetic approach to medium‐ and large‐ring systems.
Cyclopropyl Building Blocks for Organic Synthesis, 37. Synthesis and Diels—Alder Reactions of 2‐Substituted 2‐Cyclopropylideneacetates in Comparison with Allenecarboxylate and Ordinary Acrylates
Authors: de Meijere Armin , Teichmann Stephan , Seyed‐Mahdavi Fereydoun , Kohlstruk Stephan 
Published: July 2007

AbstractSeveral new 2‐substituted 2‐cyclopropylideneacetates 1a‐X (X=F, N3, SPh, OTBDMS, OTBDPS) have been prepared. Their cycloadditions and those of some previously described compounds of type 1a‐X (X=H, Br, Cl) with furan (5) and/or 6,6‐dimethylfulvene (7) are reported. Several of these peculiar acrylates 1a‐X (X=H, Br, Cl, F, N3), as well as allenecarboxylate 1b, regular acrylate 1c, crotonate 1d, and 3,3‐disubstituted acrylates 1e‐X (X=H, Cl), were reacted with furan (5) and 6,6‐dimethylfulvene (7) in two series of competition experiments at 64°C. The [2 + 4] cycloaddition of 1a‐Cl and 1a‐Br to furan (5) are both about 16 times as fast and to dimethylfulvene (7) 230 and 210 times as fast as that of the parent acrylate 1c, while allenecarboxylate 1b reacts with 4 only 30 times as fast as 1c, and the 3‐substituted acrylates 1d and 1a‐X (X=H, Cl) were all too sluggish to react under these conditions. The kinetic data obtained for the cycloadditions of 1a‐X suggest a mechanism involving either diradicals or zwitterions as intermediates.
Coupling of Alkynyl(2,4,6‐tri‐tert‐butylphenyl)phosphanes with Cuprous Chloride
Authors: Märkl Gottfried , Hennig Rüdiger 
Published: July 2007

AbstractCoupling of alkynyl(2,4,6‐tri‐tert‐butylphenyl)phosphanes 2 with n‐butyllithium and cuprous chloride gives 3,4‐diphospha‐1,5‐hexadiynes 3 or cuprous chloride complexes 8 of 3,4‐bis(phosphinidene)cyclobutenes 5, depending on the bulkiness of the substituent at the triple bond. The exclusive formation of racemic 3,4‐diphospha‐1,5‐hexadiynes 3, which was proven by 31P‐ and 13C‐NMR spectroscopy, explains the stereoselective rearrangement to only symmetrical cyclobutenes 5.
Electron‐Transfer Chemistry and Redox‐Switching of Stilbene‐Like Heteroaromatic Compounds — Syntheses, Optoelectrochemical and ESR/ENDOR Studies
Authors: Spreitzer Hubert , Scholz Markus , Gescheidt Georg , Daub Jörg 
Published: July 2007

AbstractRedox‐active compounds, in which the electron donor and the acceptor subunits are covalently linked by a vinylene spacer group were synthesised and their properties were investigated by cyclovoltammetry, spectroelectrochemistry, and ESR/ENDOR spectroscopy. — 10‐Methylphenothiazinyl, 10‐methylphenoxazinyl, and phenoxathiinyl were used as electron‐donating groups whereas 9,10‐anthraquinon‐2‐yl and phenyl groups were employed as acceptors. The synthesis of the push‐pull‐substituted stilbenes 1a, 1b, 1c, 2a, 2b and 2c was achieved by Wittig coupling of the heterocyclic aldehydes with the anthraquinoyl or phenyl phosphonium salts. The diastereoisomers were separated either by chromatography or by crystallization. — The redox potentials of the (Z) and (E) isomers differ only slightly. Spectroelectrochemical measurements indicate that the radical cations of the phenothiazine and phenoxazine derivatives undergo rearrangement from the (Z) to the (E) isomers. On the other hand, electron attachment leads to configurationally stable radical anions. This behaviour is rationalised in terms of the electron distribution reflected by the hyperfine data established by ESR/ENDOR spectroscopy.
A Facile Stereoselective Synthesis of Sphingosine and Ceramide
Authors: Li Yun‐Long , Wu Yu‐Lin 
Published: July 2007

AbstractFlexible syntheses of sphingosine and ceramide were achieved by using D‐xylose as the chiral pool and a CuCN‐catalyzed allylic alkylation reaction of a dimesylate 8 for chain elongation with concomitant control of an E configuration of the double bond.
Secondary Metabolites by Chemical Screening, 34. – Aspinolides and Aspinonene/Aspyrone Co‐Metabolites, New Pentaketides Produced by Aspergillus ochraceus
Authors: Fuchser Jens , Zeeck Axel 
Published: July 2007

AbstractNew 10‐membered lactones, named aspinolide A–C (3, 4, 5), and the aspinonene/aspyrone co‐metabolites, named trienediol (6), isoaspinonene (7), dihydroaspyrone (8), and dienetriol 9 were discovered by chemical screening methods in the cultures of Aspergillus ochraceus (DSM‐7428) under altered fermentation conditions. The structures were established by detailed spectroscopic analysis. The polyketide origin of the skeleton and the biogenesis of the oxygen atoms were verified by feeding sodium [1,2‐13C2]acetate and [18O2] gas, respectively, to growing cultures of the fungus. A comprehensive discussion of the supposed biosynthetic pathways draws the conclusion that two polyketide synthases (PKSα, PKSβ) exist, forming two different series of pentaketides in parallel. One pathway leads to branched‐chain metabolites by a Favorski‐like rearrangement of an epoxide intermediate, while the other involves detachment of the pentaketides from the PKSβ by lactonisation without any rearrangement of the carbon skeleton. The former pathway is affected by an inhibitor of cytochrome P450 dependent monooxygenases.
Synthesis of S‐α‐D‐Glucosylated L‐Cysteine – A Novel S‐Glycosyl Amino Acid
Authors: Käsbeck Ludwig , Kessler Horst 
Published: July 2007

AbstractWhereas S‐β‐D‐glucosylated L‐cysteine is easily available, the corresponding α‐anomer has not been prepared before. In this paper a solution to the synthetic problem is presented. The glycosylation of highly nucleophilic N‐phthaloyl‐L‐cysteine esters 4 and 5 with 2,3,4,6‐tetra‐O‐benzyl‐α‐L‐glucopyranosyl trichloroacetimidate in the presence of 1 equivalent of BF3 · Et2O provided the protected cysteinyl‐S‐α‐glycosides 6 and 7 in good yields. These S‐α‐glycosylated cysteine derivatives were only available by use of the non‐urethane N‐protected glycosyl acceptors 4 and 5. Palladium‐catalyzed hydrogenolysis and subsequent hydrazinolysis of the benzylated compound 7 afforded L‐cysteinyl‐S‐α‐D‐glucoside 1, a novel S‐glycosyl amino acid.
1,3‐Dipolar Cycloadditions, 97. – Some Cycloadditions of Aromatic Thione S‐Oxides
Authors: Huisgen Rolf , Mloston Grzegorz , Polborn Kurt , Palacios‐Gambra Francisco 
Published: July 2007

AbstractSurprisingly, thiobenzophenone S‐oxide (5) and thione 6 afforded the spiro‐1,2,4‐trithiolane 7 (86%) instead of the expected spiro‐1,2,4‐oxadithiolane 16. Structure 7 was established via spectra, single‐crystal X‐ray analysis, and an independent synthesis from thiobenzophenone S‐sulfide (15) and 6. On accepting the formation of 16 by 1,3‐cycloaddition as a first step, we reduced the mechanistic problem to the conversion 16 + 6 → 15 + dione 8; three conceivable pathways are discussed. Thiofluorenone S‐oxide (25) combines with 6 to the trithiolane 27 in low yield; the spontaneous conversion of 25 to 9,9′‐bifluorenylidene (26) takes precedence. No 1,3‐cycloaddition is involved in the 1:1 reaction of 5 with (E)‐cyclooctene (28); 5 combines as a hetero‐1,3‐diene with 28 to a Diels‐Alder type adduct 30.
Application of the Chelate‐Enolate Claisen Rearrangement to The Synthesis of γ,δ‐Unsaturated Amino Acids
Authors: Kazmaier Uli 
Published: July 2007

AbstractDeprotonation of N‐protected amino acid allylic esters with LDA at −78°C and subsequent addition of a metal salt presumably results in the formation of a chelated metal enolate that undergoes Claisen rearrangement upon warming up to room temperature, giving rise to γ,δ‐unsaturated amino acids. Many different metal salts can be used for chelation, but in general the best results are obtained with zinc chloride. Due to the fixed enolate geometry, as a result of chelate formation, and a strong preference for the chair‐like transition state, the rearrangement proceeds with a high degree of diastereoselectivity. This method can be applied to acyclic as well as to cyclic substrates, and even to peptides, and allows the synthesis of amino acids containing quaternary carbon centers. Esters of chiral allylic alcohols produce optically active amino acids via chirality transfer from the ester moiety to the α‐carbon center of the amino acid. Another possibility to introduce chirality is given by the rearrangement in the presence of chiral ligands. The best results are obtained if Al(OiPr)3 is used as the chelating metal salt and the Chinchona alkaloids as bidentate ligands. Quinine gives rise to (2R)‐configured amino acids, whereas quinidine delivers the (2S) derivatives in very high yields and excellent enantioselectivities (80–93% ee). The ligands can easily be recovered nearly quantitatively from the reaction mixture.
Pigments of Fungi, 68. – Phlebiachrysoic Acids, New Inhibitors of Leukotriene Biosynthesis from Phlebia chrysocrea (Basidiomycetes)
Authors: Marumoto Ryuji , Klostermeyer Dörte , Steglich Wolfgang , Wunder Annette , Anke Timm 
Published: July 2007

AbstractFive yellow 2‐hydroxy‐5‐methoxybenzoquinones with C15 and C17 alkyl side chains were isolated from fruitbodies of the wood‐rotting fungus Phlebia chryoscrea. The compounds, named phlebiachrysoic acids A–E are strong inhibitors of leukotriene biosynthesis and are responsible for the red colour reaction when the fruitbodies are touched with aqueous alkali.
Bromine Complexes of Ethylene and Cyclopropene: Matrix‐IR‐Spectroscopic Identification, Photochemical Reactions, Ab Initio Studies
Authors: Maier Günther , Senger Stefan 
Published: July 2007

AbstractThe matrix‐isolated ethylene–bromine complex (1) and the cyclopropene–bromine complex (8) have been chosen to examine which ab initio method (MP2 or BLYP) is more suitable to calculate the IR spectra and structures of π complexes. In addition the photochemistry of 1 and 8 has been investigated and the mechanism of the photochemically induced reactions is discussed.
Enantioselective synthesis of α‐phosphanyl ketones and 2‐phosphanyl alcohols
Authors: Enders Dieter , Berg Thorsten , Raabe Gerhard , Runsink Jan 
Published: July 2007

AbstractAn efficient, highly enantioselective methodology for the synthesis of α‐phosphanyl ketones 7 and 2‐phosphanyl alcohols 12 and 13, important hemilable ligands for enantioselective homogeneous catalysis and chiral building blocks in general, has been developed. The key step of this first enantio‐selective synthesis of α‐phosphanyl ketones is the diastereo‐selective phosphanylation of SAMP hydrazones 2 to produce α‐phosphanyl hydrazones, isolated as the more stable borane adducts 6. Subsequent ozonolysis afforded α‐phosphanyl ketones 7. The enantioselective synthesis of 2‐phosphanyl alcohols 12 and 13 has been accomplished by two fundamentally different procedures: the phosphanylation of unsubstituted chiral aldehyde hydrazones 9 and the alkylation of α‐diphenylphopshanyl acetaldehyde SAMP hydrazone 10. After separation of the minor diastereomer, the borane‐protected α‐phosphanyl aldehyde hydrazones 11 were converted to unprotected 2‐phosphanyl alcohols 13 by ozonolysis, reduction and removal of the borane group. The absolute configuration of the functionalized phosphanes was determined by X‐ray analysis, NOE experiments or polarimetry.
Simple Synthesis of Both Enantiomers of 3‐Methyl‐N‐(3‐Methylbutyl)pyrrolidine
Authors: Veith Hans Jürgen , Collas Markus , Zimmer Reinhold 
Published: July 2007

Abstract(S)‐3‐Methyl‐N‐(3‐methylbutyl)pyrrolidine (1) and its antipode (R)‐1 have been prepared by reduction of (S)‐4,5‐dihydro‐3‐methyl‐2(3H)furanone (7) and dimethyl (R)‐2‐methylsuccinate (11), bromination thereof, and ring closure of the intermediates (S)‐9 and (R)‐9, respectively, with 3‐methylbutylamine (10). An alternative synthesis of (R)‐1 by mesylation of (R)‐8 is also described. Both enantiomers of 1 were obtained in excellent enantiomeric excesses (ee = 96%).
Synthesis of a Tetraazido‐Substituted 2‐Tetrazene from 1,5‐Cyclooctadiene and Iodine Azide
Authors: Rose Bernd , Schollmeyer Dieter , Meier Herbert 
Published: July 2007

AbstractIn contrast to the addition of iodine azide to cyclooctene (1) or 1,3‐cyclooctadiene (5), its reaction with 1,5‐cyclooctadiene (12) leads mainly to the surprisingly stable tetraazido‐substituted 2‐tetrazene 14 The structure of this was established by 15N‐NMR studies and an X‐ray structural analysis. Treatment of 14 with hydrochloric acid yields the diazido‐substituted 9‐azabicyclo[3.3.1]nonane 20.
Synthesis of Optically Active 2‐Siloxycyclopropanecarboxylates by Asymmetric Catalysis, IV. – Influence of Nucleophilicity of Silyl Enol Ethers on Stereoselectivities in Asymmetric Cyclopropanation Reactions
Authors: Schumacher Ralf , Reißig Hans‐Ulrich 
Published: July 2007

AbstractBy variation of the aryl substituents of silyl enol ethers 1a–e and 1f–k, the influence of their nucleophilicity on the stereochemical outcome of cyclopropanation reactions was studied. Using the neutral Schiff‐base catalyst 2 · Cu(OAc)2, there was only a weak effect. On the other hand, with the cationic bisoxazoline complex 3· CuOTf a remarkable increase in the enantioselectivity was observed with more strongly electron‐attracting substituents such as a trifluoromethyl or nitro group.
Probing for Steric and Electronic Effects in Diastereoselective Dioxirane Epoxidations Compared to The Oxygen Transfer by Peroxy Acids
Authors: Adam Waldemar , Paredes Rodrigo , Smerz Alexander K. , Veloza L. Angela 
Published: July 2007

AbstractThe spiro transition state for the oxygen transfer by dioxiranes is substantiated by the fact that no enhanced steric effects are observed when dioxiranes with alkyl groups of different size are employed, as manifested by the same (within the experimental error) diastereoselectivities in the epoxidation of 2‐menthene and 1,3‐dimethylcyclohexene for different dioxiranes. The π‐facial selectivity (anti attack) in the epoxidation of the acetate and the methyl and trimethylsilyl ether derivatives of 2‐cyclohexenol derives from steric interactions, whereas a pronounced electronic effect (electrostatic repulsion) is held responsible for the high anti selectivity of peroxides such as ascaridol and 3‐hydroperoxycyclohexene. Quite generally, dioxiranes display only slightly higher diastereoselectivities than mCPBA in sterically controlled epoxidations of cycloalkenes.
Utilization of Industrial Waste Materials, 7. – Synthesis of New, Chiral β‐sec‐Amino Alcohols – Regio‐ and Diastereoselective α‐Hydroxyalkylation of (1R,5R)‐2‐Azabicyclo[3.3.0]octane
Authors: Wilken Jörg , Martens Jürgen 
Published: July 2007

AbstractNew, chiral β‐sec‐amino alcohols 3a–d, 4a–e, and 5a–h have been synthesized from the enantiomerically pure amine (all‐R)‐2a. For the diastereo‐ and regioselective α‐hydroxyalkylation of the chiral (all‐R)‐N‐nitroso‐2‐azabicyclo[3.3.0]octane (all‐R)‐2d, Seebach's “one pot” method was chosen. The versatile nucleophilic intermediate reacts regio‐and stereoselectively with a variety of electrophiles to afford 3‐substituted pyrrolidine derivatives, e.g. (erythro)‐(αR,βS)‐amino alcohol frameworks with four sterically crowded stereogenic centers, and (βS)‐configured tricyclic structures with a cycloalkynol building block (see formulae 3a–d, 4a–e, and 5a–h). Alkylation products are obtained in fair yields with a high degree of stereoselectivity (diastereomeric ratios dr up to 93:7). A mechanistic interpretation of the stereochemical course of this reaction is presented. – This is a further example of the synthesis of interesting new chiral ligands from the industrial waste material (all‐R)‐2‐azabicyclo[3.3.0]octane‐3‐carboxylic acid benzyl ester (all‐R)‐1a. The catalytic ability of selected (erythro)‐ and new, related stereoisomeric amino alcohol structures were tested in the enantioselective borane reduction using the prochiral acetophenone as model substrate (enantiomeric excesses ee up to 86%).
Utilization of Industrial Waste Materials, 10. – Synthesis of New Chiral Bicyclic 3‐hydroxypiperidines – Highly Diastereoselective Ring Expansion of the Azabicyclo[3.3.0]octane System to Chiral Piperidine Derivatives
Authors: Wilken Jörg , Kossenjans Michael , Saak Wolfgang , Haase Detlev , Pohl Siegfried , Martens Jürgen 
Published: July 2007

AbstractNew, chiral bicyclic 3‐hydroxypiperidines (4S)‐2a–e are synthesized from the β‐amino alcohols (3R)‐1a–e. In an one‐step reaction (4S)‐2a–e are obtained by a high diastereoselective ring expansion (dr ⩾ 95:5). As well, the amino alcohol (3S)‐1a leads to the corresponding rearranged epimer bicyclic piperidine derivative (4R)‐2a (dr ⩾ 95:5). Thus, it is possible to clarify the influence of the three stereogenic centers of the parent compound regarding the diastereoselectivity of the ring expansion. After oxidation of the tert‐amino sec‐alcohol (4S)‐2a to the corresponding α‐amino ketone 4, new 3‐hydroxypiperidines (4Ξ)‐5a, b12 and (4RS)‐6 are obtained by a diastereoselective Grignard addition. Furthermore, the achiral and the chiral reduction of 4 to the β‐amino alcohols (4S)‐2a and (4R)‐2a is described. These are further examples of the utilization of industrial waste material (all‐R)‐2‐azabicyclo[3.3.0]octane‐3‐carboxylic acid (all‐R)‐3.
Total Synthesis of the Toxin Oosponol and of Structural Analogues and Investigation of Their Antibiotic Activities
Authors: Kovács Tibor , Sonnenbichler Isolde , Sonnenbichler Johann 
Published: July 2007

AbstractThe toxic metabolite of the basidiomycete Gloeophyllum abietinum, oosponol (6b), and the structural analogues (Figure 1) were synthesised in order to investigate which partial structures of the molecules are responsible for their biological activities. Different organisms were employed to test the antibiotic activities of the analogues. From the results obtained with the synthetic analogues of oosponol (6b), it became evident that the toxicity of this fungal metabolite can be attributed to a vinylogous acid anhydride structure, which in nature is produced by dehydrogenation of the nontoxic precursor oospoglycol (7).
Pheromone Synthesis, CLXXXIII. Synthesis of (1R,2R,5S,7R)‐ and (1R,2S,5S,7R)‐2‐hydroxy‐exo‐Brevicomin, the Components of the Male‐Produced Volatiles of the Mountain Pine Beetle, dendroctonus ponderosae
Authors: Takikawa Hirosato , Shimbo Ken‐Ichiro , Mori Kenji 
Published: July 2007

AbstractBoth (2R)‐ and (2S)‐hydroxy derivatives of (+)‐exo‐brevicomin {5‐methyl‐6,8‐dioxabicyclo[3.2.1]octan‐2‐ol; 1 and 2} were synthesized by employing Sharpless asymmetric dihydroxylation as the key reaction.
Pheromone Synthesis, CLXXXII. Synthesis of (1R,1′R,5′R,7′R)‐ and (1S,1′R,5′R,7′R)‐ 1‐hydroxy‐exo‐Brevicomin, the Components of the Male‐Produced Volatiles of the Mountain Pine Beetle, dendroctonus ponderosae
Authors: Yokoyama Yūsuke , Mori Kenji 
Published: July 2007

AbstractBoth (1R)‐ and (1S)‐hydroxy derivatives of (+)‐exo‐brevicomin {(1R,1′R,5′R,7′R)‐1‐(5′‐methyl‐6′,8′‐dioxabicyclo[3.2.1]‐octyl)ethanol (1) and its (1S)‐isomer (2)} were synthesized by employing Sharpless asymmetric dihydroxylation as the key reaction.
Synthesis of the Thio‐Linked Ganglioside GM3 epitope
Authors: Eisele Thomas , Schmidt Richard R. 
Published: July 2007

AbstractThe synthesis of sulfur‐linked GM3 epitope 2 is based on acid‐catalyzed and base‐promoted S‐glycosylation processes. As a precursor, 2‐O‐benzoyl‐3‐thiogalactoside 10 was required, and was obtained from 4,6‐O‐benzylidene‐galactoside 3 in six high‐yielding steps. Base‐promoted S‐glycosylation of 10 with neuraminic acid functionalized β‐halogenose 11 in the presence of NaH as base and Kryptofix 21 as coactivator afforded α(2‐3)‐thio‐linked disaccharide 13, which was readily converted to α‐halogenose 20. Heptyl 1‐thioglycoside 22 was obtained from O‐galactosyl trichloroacetimidate 21 and heptylthiol via acid‐catalyzed S‐glycosylation. 22 was transformed into 2,3,6‐tri‐O‐acylgalactoside 26 which, via the 4‐O‐triflate and treatment with potassium thioacetate, followed by selective removal of the S‐acetyl group, furnished the 2,3,6‐tri‐O‐acyl‐4‐thioglucoside 28. Base‐promoted S‐glycosylation of 28 with halogenose 20 led to fully acylated target molecule 29, which was quantitatively converted into 2.