bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anchoring Fe Ions to Amorphous and Crystalline Oxides: A Means To Tune the Degree of Fe Coordination
Authors: Berlier Gloria , Bonino Francesca , Zecchina Adriano , Bordiga Silvia , Lamberti Carlo 
Published: October 2003

AbstractWe report on an IR spectroscopic study on the room‐temperature adsorption of NO on different iron(II)‐containing siliceous matrices. Fe2+ hosted inside the channels of MFI‐type zeolites (Fe‐ZSM‐5 and Al‐free Fe‐silicalite) exhibits pronounced coordinative unsaturation, as witnessed by the capability to form, at 300 K, [Fe2+(NO)], [Fe2+(NO)2] and [Fe2+(NO)3] complexes with increasing NO equilibrium pressure. Fe2+ hosted on amorphous supports (high surface area SiO2 and MCM‐41) sinks more deeply into the surface of the siliceous support and thus exhibits less pronounced coordinative unsaturation: only [Fe2+(NO)2] complexes were observed, even at the highest investigated NO equilibrium pressures. Activation at higher temperature (1073 K) of the Al‐free Fe‐silicalite sample resulted in the appearance of Fe2+ species similar to those observed on SiO2 and MCM‐41, and this suggests that local (since not detectable by X‐ray diffraction) amorphisation of the environment around Fe2+ anchoring sites occurs. The fact that this behaviour is not observed on the Fe‐ZSM‐5 sample activated at the same temperature suggests that framework Al species (and their negatively charged oxygen environment) have an important role in anchoring extraframework Fe2+ species. Such an anchoring phenomenon will prevent a random migration of iron species, with subsequent aggregation and loss of coordinative unsaturation. These observations can thus explain the higher catalytic activity of the Fe‐ZSM‐5 system in one‐step benzene to phenol conversion when compared with the parent, Al‐free, Fe‐silicalite system with similar Fe content. The nature of the support and the activation temperature can therefore be used as effective means to tune the degree of Fe coordination.
Excited‐State Proton‐Relay Dynamics of 7‐Hydroxyquinoline Embedded in a Solid Matrix of Poly(2‐hydroxyethyl methacrylate)
Authors: Kwon Oh‐Hoon , Doo Hyungie , Lee Young‐Shin , Jang Du‐Jeon 
Published: October 2003

AbstractExcited 7‐hydroxyquinoline embedded in a solid matrix of poly(2‐hydroxyethyl methacrylate) undergoes a proton‐relay reaction efficiently to form its keto tautomer. However, the reaction mechanism depends on the torsional conformation and the microscopic environment of the molecule at the moment of excitation. Whereas the bridged cis‐enol form undergoes proton relay immediately on absorption of a photon to produce its tautomeric keto species, the unbridged cis form requires 120 ps for bridge formation via solvent reorganization prior to proton relay. Furthermore, the trans form needs 1000 ps for tautomerization because it requires an activated (11 kJ mol−1) torsional motion to change into its cis form prior to bridge formation and proton relay. Torsional motion rather than solvent reorganization determines the proton relay rate of the trans‐form of the molecule.
Structural Forces near Phase Transitions of Liquid Crystals
Authors: Kočevar Klemen , Muševič Igor 
Published: October 2003

AbstractThe structure of the fragile liquid‐crystalline phases has a strong impact on the forces between bodies immersed in a liquid crystal (LC). We have equipped an atomic force microscope with a precise temperature control and measured various liquid‐crystalline structural forces at temperatures close to the phase transitions. The observed forces agree well with predictions of Landau–de Gennes phenomenological theory of LCs, even at a nanoscale length. In addition to this, we have observed a molecular layer, adsorbed on the surfactant‐covered glass surface, and determined its thickness and elastic properties.
A Theoretical Study of the UV/Visible Absorption and Emission Solvatochromic Properties of Solvent‐Sensitive Dyes
Authors: Han Wen‐Ge , Liu Tiqing , Himo Fahmi , Toutchkine Alexei , Bashford Donald , Hahn Klaus M. , Noodleman Louis 
Published: October 2003

AbstractUsing the density‐functional vertical self‐consistent reaction field (VSCRF) solvation model, incorporated with the conductor‐like screening model (COSMO) and the self‐consistent reaction field (SCRF) methods, we have studied the solvatochromic shifts of both the absorption and emission bands of four solvent‐sensitive dyes in different solutions. The dye molecules studied here are: S‐TBA merocyanine, Abdel‐Halim's merocyanine, the rigidified aminocoumarin C153, and Nile red. These dyes were selected because they exemplify different structural features likely to impact the solvent‐sensitive fluorescence of “push‐pull”, or merocyanine, fluorophores. All trends of the blue or red shifts were correctly predicted, comparing with the experimental observations. Explicit H‐bonding interactions were also considered in several protic solutions like H2O, methanol and ethanol, showing that including explicit H‐bonding solvent molecule(s) in the calculations is important to obtain the correct order of the excitation and emission energies. The geometries, electronic structures, dipole moments, and intra‐ and intermolecular charge transfers of the dyes in different solvents are also discussed.
Cover Picture: Experimental Detection of the H2NO3 Radical (ChemPhysChem 10/2003)
Authors: Cacace Fulvio , de Petris Giulia , Troiani Anna 
Published: October 2003

AbstractThe cover pictures shows…︁‥the mass spectrum of nitrogen hydroxide oxide, the H2NO3. radical, which was discovered by neutralization reionization mass spectrometry (NRMS) and characterized as a relatively long‐lived (over 1 μs) metastable species. The discovery required the availability of the appropriate charged precursor that fortunately had previously been prepared by this group (1989) as a result of their sustained interest in gas‐phase ion chemistry of nitrates, nitrites and related molecules. Cacace et al. found that protonation of nitric acid by strong Brønsted acids yields, in addition to the H2ONO2+ ion, smaller amounts of the less stable (HO)2NO+ isomer, namely charged nitrogen hydroxide oxide. This result has allowed the present discovery by NRMS (yellow trace), whereas NRMS of the H2ONO2+ ion does not result in detectable H2NO3. neutral species (green trace). The importance of nitrogen hydroxide oxide stems from its relevance to a variety of research areas, from the reduction of the NO32− anion, to atmospheric chemistry, radiolysis of nuclear‐waste solutions, the charge‐transfer mechanism of aromatic nitration, etc. Find out more in the communication by Cacace et al. on pp. 1128–131.
Theoretical Search for Anions Possessing Large Electron Binding Energies
Authors: Sobczyk Monika , Sawicka Agnieszka , Skurski Piotr 
Published: October 2003

AbstractThe vertical electron detachment energies (VDE) of several anions were calculated at the OVGF level with 6‐311++G(d) basis sets. The negatively charged species studied were chosen based on the observation that the largest electron binding energies for such systems are expected to be found for the anions whose neutral parents are polynuclear superhalogens. The largest vertical electron binding energy of 12.63 eV was found for Ta3F16−, and this is the largest excess electron binding energy of a molecular system reported in the literature thus far. Moreover, the VDEs of 12.63 and 12.20 eV calculated for Ta3F16− and As3F16−, respectively, exceed the upper limit for the excess electron binding energy (thought to be 12 eV). Several other anions were also found [at the OVGF/6‐311++G(d) level] to possess very large VDEs (i.e. Al2Br7−: 7.08 eV, Al2Cl7−: 7.75 eV, Al2F7−: 11.16 eV, P2F11−: 10.95 eV, V2F11−: 10.98 eV, As2F11−: 11.43 eV, and Ta2F11−: 11.84 eV). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Structures of the Octahedral Persulfuranes H4SF2, H2SF4, Me2SH4 and Me2SF4, and Activation Enthalpies for Their cis/trans Isomerization
Authors: Steudel Yana , Steudel Ralf 
Published: October 2003

AbstractEight hypothetical persulfurane molecules of the type X2SY4 (X, Y = H, F, Me) have been studied by ab initio MO calculations at the G3(MP2) level of theory. Depending on the substituents either the cis or the trans isomers of these octahedral molecules are most stable. While H4SF2 is most stable as the cis isomer, the global minimum structures of H2SF4, Me2SH4, and Me2SF4 are the trans isomers. The enthalpy differences between the corresponding isomers are in the range 7−53 kJ·mol−1. The transition states for the intramolecular cis ⇋ trans isomerization have been located in all cases. Starting from the global minimum geometries the activation enthalpies (ΔH#298) for this isomerization are in the range 199−263 kJ·mol−1, indicating rather rigid structures. Therefore, it should be possible to isolate both isomers at low to moderate temperatures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Chain‐Like Tetra‐, Penta‐ and Heptanuclear Cyanide‐Bridged Complexes by Attachment of Organometallic Cyanides to M2, M3 and M5 Units
Authors: Sheng Tianlu , Appelt Ralf , Comte Virginie , Vahrenkamp Heinrich 
Published: October 2003

AbstractAttachment of the “ligands” [Cp(dppe)Fe‐CN], [Cp(PPh3)2Ru‐CN], [Cp(CO)2Fe‐CN] and [(CO)5M‐CN]−, (where M = Cr, Mo, W) to the polymetallic centres [Ru2(OAc)4]+, [Co3(dpa)4]2+ and [Ni5(tdpa)4]2+ yielded two tetra‐, three penta‐ and five heptanuclear complexes with chain‐like linear arrangements of the metal ions and the bridging cyanide ligands, as proved by the structure determination of [Ni5(tdpa)4{Cp(dppe)2Fe‐CN}2](PF6)2. IR and CV data show that the Ru2, Co3 and Ni5 centres of these complexes withdraw electron density from the external organometallic units. This prevents electronic interactions between the two terminal metal ions, yet allows multistep one‐ and two‐electron redox processes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis and Characterization of Oxorhenium and Oxotechnetium Complexes with a Novel Tetradentate N3O Bifunctional Agent
Authors: Papachristou Maria , Pirmettis Ioannis , Siatra‐Papastaikoudi Theodora , Pelecanou Maria , Tsoukalas Charalambos , Raptopoulou Catherine P. , Terzis Aris , Chiotellis Efstratios , Papadopoulos Minas 
Published: October 2003

AbstractThe novel tetradentate N3O bifunctional agent 3‐hydroxy‐4‐[2‐(2′‐pyridinecarboxamido)acetylamino]benzoic acid (1), reacts with [Bu4N][ReOCl4] or [Bu4N][99gTcOCl4] in EtOH resulting in neutral and stable oxorhenium 2 or oxotechnetium‐99 g 3 complexes. Both complexes were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy. X‐ray analysis of 2 showed that the rhenium atom is pentacoordinate presenting a distorted square‐pyramidal coordination geometry. The analogous oxotechnetium‐99m complex 4 was also prepared quantitatively by the reaction of ligand 1 with Na99mTcO4 in isotonic saline using tin chloride as reducing agent. Its identity was established by chromatographic comparison to the oxorhenium 2 and oxotechnetium 3 complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Binuclear Copper(II) Acetate Complex Showing a 3D Supramolecular Network with Hydrophilic Pockets: Its Unusual Magnetic Behaviour
Authors: Fondo Matilde , García‐Deibe Ana M. , Sanmartín Jesús , Bermejo Manuel R. , Lezama Luis , Rojo Teófilo 
Published: October 2003

AbstractThe binuclear complex [Cu2L(OAc)]·6H2O (1) {H3L = 2‐(2‐hydroxyphenyl)‐1,3‐bis[4‐(2‐hydroxyphenyl)‐3‐azabut‐3‐enyl]‐1,3‐imidazolidine} which shows an unusual magnetic superexchange behaviour, acts as a building block for a novel three‐dimensional metal‐organic framework, with hydrophilic pockets. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Selective Aromatic N‐Substitution with N‐(4‐Tolyl)hydroxylamine by Addition of Polar Aprotic or Diethereal Solvent
Authors: Takeuchi Hiroshi , Tateiwa Jun‐ichi , Hata Suguru , Tsutsumi Keisuke , Osaki Yoshinori 
Published: October 2003

AbstractAmination of anisole and toluene with N‐(4‐tolyl)hydroxylamine in trifluoroacetic acid was tuned to regioselectively provide the corresponding diarylamine by partial replacement of trifluoroacetic acid with a polar aprotic or a diethereal solvent. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Radical Version of the Bromo‐ and the Iodocyclization of Bis(homoallylic) Alcohols — The Synthesis of Halogenated Tetrahydrofurans by Stereoselective Alkoxyl Radical Ring Closures
Authors: Hartung Jens , Kneuer Rainer , Laug Stefanie , Schmidt Philipp , Špehar Kristina , Svoboda Ingrid , Fuess Hartmut 
Published: October 2003

AbstractA new synthesis of bromo‐ and iodomethyl‐substituted tetrahydrofurans has been devised. The sequence starts with the conversion of aryl‐functionalized bis(homoallylic) alcohols1intoN‐alkenoxythiazole‐2(3H)‐thiones6or pyridine‐2(1H)‐thiones7. When photolyzed in the presence of appropriate trapping reagents, thiones6and7efficiently liberated substituted 4‐penten‐1‐oxyl radicals2, which underwent synthetically useful 5‐exo‐trig cyclizations. Cyclized radicals3were trapped with BrCCl3or an adequate iodine atom donor (eithern‐C4F9I or diethyl 2‐iodo‐2‐methyl malonate) to provide halocyclization products4or5. This strategy has been applied for the synthesis of 3‐, 4‐, or 5‐phenyl‐substituted 2‐(1‐bromo‐1‐methylethyl)tetrahydrofurans4a−c(75−90%, 36−96%de), which were not attainable as major products from polar, for example NBS‐mediated, bromocyclizations. Aryl‐substituted 2‐iodomethyl tetrahydrofurans5(46−80%) were prepared in a similar way starting fromN‐alkenoxypyridine‐2(1H)‐thiones7and a suitable iodine atom donor. Diastereomerically pure iodidescis‐5andtrans‐5served as starting materials for a stereochemical analysis of disubstituted tetrahydrofurans by NMR spectroscopy and X‐ray diffraction analysis. The results of this investigation clarified that all new alkoxyl radical cyclizations followed in terms of regio‐ and diastereoselectivity the general guidelines which had been established for this type of ring‐closure reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
3‐Nitrocoumarin Amidines: A New Synthetic Strategy for Substituted [1]Benzopyrano[3,4‐d]imidazol‐4(3H)‐ones
Authors: Beccalli Egle M. , Contini Alessandro , Trimarco Pasqualina 
Published: October 2003

AbstractA new synthesis of substituted [1]benzopyrano[3,4‐d]imidazol‐4(3H)‐ones, starting from 3‐nitrocoumarin N‐functionalized amidines 3, has been developed. When the 3‐nitro‐amidines 3 were treated with NaBH4 in the presence of 10% palladium on charcoal, 2‐substituted [1]benzopyrano[3,4‐d]imidazol‐4(3H)‐ones 4 were produced. Structure elucidation of compounds 4 revealed that they exist as one of the three possible tautomeric structures (i.e., 4dα). Alkylation of 4d to give 6, as well as NOE experiments on 6 and energy calculations allowed the most favoured structure of the 4 derivatives to be identified. Alternatively, the reduction of the 3‐nitro‐amidines 3 by triethyl phosphite, through a nitrene intermediate, cyclization and a [1.5] sigmatropic shift, yielded 2‐morpholino‐3‐alkyl‐[1]benzopyrano[3,4‐d]imidazol‐4(3H)‐ones 7. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Episulfidation of trans‐Cyclooctene with an 1,2,4‐Oxadithiolane
Authors: Adam Waldemar , Bargon Rainer M. , Mloston Grzegorz 
Published: October 2003

AbstractThe dipolar cycloaddition of thiobenzophenone S‐oxide (1) and 2,2,4,4‐tetramethyl‐3‐thioxocyclobutanone (2) generates the labile 1,2,4‐oxadithiolane I, which in the presence of trans‐cyclooctene (3) affords trans‐episulfide (9). In this direct sulfur transfer, the oxathiirane II and/or the dithiirane IV, both derived from the 1,2,4‐oxadithiolane I, are proposed as elusive episulfidating agents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Tunable One‐Step N,N′‐Disubstitution of 1,4,8,11‐Tetraazacyclotetradecane with Acrylamide
Authors: Fensterbank Hélène , Berthault Patrick , Larpent Chantal 
Published: October 2003

AbstractN,N′‐disubstitution of cyclam without the use of protecting groups was investigated. This macrocycle reacted with two equivalents of a Michael acceptor in chloroform to yield as a major isolated compound the 1,8 di‐N,N′‐substituted macrocycle. Running the same reaction in the presence of one equivalent of para‐toluenesulfonic acid led to the 1,11‐di‐N,N′‐substituted macrocycle as the major product. Each regioisomer has been isolated and fully characterized. The observed regioselectivity is discussed with respect to the reactivity of the unprotonated or protonated monoalkylated intermediate. A site of protonation for the latter intermediate is deduced from an NMR study. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Recent Advances in the Synthesis of Spermine and Spermidine Analogs of the Shark Aminosterol Squalamine
Authors: Brunel Jean Michel , Letourneux Yves 
Published: October 2003

AbstractGreat attention has recently been focused on the shark aminosterol squalamine (1) because of its important antimicrobial and antiangiogenic activities. Herein, we present the different series of spermine and spermidine analogs that have been synthesized. Many of the squalamine mimics demonstrate a broad spectrum activity against microorganisms. Squalamine is currently undergoing Phase II clinical trials in cancer patients. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of Differently Disubstituted 2,2′‐Bipyridines by a Modified Negishi Cross‐Coupling Reaction
Authors: Lützen Arne , Hapke Marko , Staats Holger , Bunzen Jens 
Published: October 2003

AbstractA general practical approach to a number of differently disubstituted 2,2′‐bipyridines from substituted 2‐bromo‐ and 2‐chloropyridines by application of modified Negishi cross‐coupling conditions has been developed. These 2,2′‐bipyridines carry versatile functional groups that can be elaborated further, as demonstrated for some examples. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
New One‐Pot Synthesis of 3‐Alkyl‐ and 3‐(ψ‐Hydroxyalkyl)oxindoles from Isatins
Authors: Volk Balázs , Simig Gyula 
Published: October 2003

AbstractA new and efficient one‐pot procedure has been developed for the synthesis of 3‐alkyl‐ and 3‐(ψ‐hydroxyalkyl)oxindoles from isatins by treatment with alcohols and diols in the presence of Raney nickel, under hydrogen atmosphere. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Chagosensine, a New Chlorinated Macrolide from the Red Sea Sponge Leucetta chagosensis
Authors: Řezanka Tomáš , Hanuš Lumír , Dembitsky Valery M. 
Published: October 2003

AbstractChagosensine, a sixteen‐membered chlorinated macrolide, was isolated from the Red Sea calcareous sponge Leucetta chagosensis. Its structure was elucidated mainly on the basis of NMR spectroscopic data. The relative and absolute configurations were determined by analysis of 1H and 13C NMR, NOESY, and CD data, by the modified Mosher’s method, and by using degradation products. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Flexible Asymmetric Synthesis of anti‐1,2‐Sulfanyl Amines
Authors: Enders Dieter , Moll Alexander , Schaadt Annette , Raabe Gerhard , Runsink Jan 
Published: October 2003

AbstractAn efficient and flexible asymmetric synthesis of various protected anti‐1,2‐sulfanyl amines bearing two adjacent stereogenic centres is described. Key steps are the diastereoselective α‐alkylation of α‐sulfanylated acetaldehyde‐SAMP‐hydrazones with various electrophiles and subsequent nucleophilic 1,2‐addition of organocerium reagents to the hydrazone CN double bond. The resulting hydrazines were converted into the title compounds with excellent diastereomeric and enantiomeric excesses (de and ee values ⩾ 96%) by reductive N,N bond cleavage to remove the chiral auxiliaries and protection of the amino functions. The relative and absolute configurations were determined by NOE experiments and X‐ray structure analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Organic Chemistry of Vitamin D Analogues (Deltanoids)
Authors: Posner Gary H. , Kahraman Mehmet 
Published: October 2003

AbstractAn increasing number of synthetic vitamin D analogues (deltanoids) are now being used as sensitive molecular biology probes and also as new drug candidates and new drugs for treatment of various human diseases. The design and stereocontrolled synthesis of such new deltanoids are guided by considering catabolism inhibition and by using large steroidal chirons and small steroid‐derived chirons. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Azido/Tetrazole Tautomerism in 2‐Azidoadenine β‐D‐Pentofuranonucleoside Derivatives
Authors: Lioux Thierry , Gosselin Gilles , Mathé Christophe 
Published: October 2003

AbstractThe β‐D‐ribofuranoside derivative of 2‐azidoadenine and its 2′‐deoxy‐, 2′,3′‐dideoxy‐ and 2′,3′‐dideoxy‐2′,3′‐didehydro counterparts have been synthesized. All these compounds were obtained through the preparation of their 2‐chloro precursors. These were converted into their 2‐hydrazino derivatives, which upon treatment with sodium nitrate in acid medium gave the target nucleosides. The azido/tetrazole tautomerism observed in such nucleoside analogues was studied in detail. The compounds were also tested for their activity against HIV and HBV, but did not show significant antiviral effects. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Electrophilic Cyclization of 1,6‐Dienes Containing an Allylsilane Moiety − Enantioselective Synthesis of cis‐ and trans‐γ‐Irone
Authors: Beszant Stephen , Giannini Elios , Zanoni Giuseppe , Vidari Giovanni 
Published: October 2003

AbstractIn this paper, we report the first examples of Lewis acid and mercuric trifluoroacetate promoted cyclizations of 1,6‐dienes containing an allylsilane moiety. Mercuric trifluoroacetate has been proved to be the reagent of choice leading to methylenecyclohexane derivatives in good yields and with complete regioselectivity albeit with poor diastereoselectivity. Using this methodology a stereodivergent synthesis of enantiomerically pure (−)‐(2S,6R)‐cis‐γ‐irone and (−)‐(2S,6S)‐trans‐γ‐irone, two precious aroma constituents, has been accomplished. This represents an innovative approach with respect to previous syntheses of γ‐irones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of Dihydrodiosgenin Glycosides as Mimetics of Bidesmosidic Steroidal Saponins
Authors: Suhr René , Lahmann Martina , Oscarson Stefan , Thiem Joachim 
Published: October 2003

AbstractThe focus of this work is the synthesis of bidesmosidic saponin mimetics. Therefore, dihydrodiosgenin derivatives, which differ from the natural compounds by reduction of the 22‐(hemi) acetal were used as glycosyl acceptors. In preliminary studies, the dihydrodiosgenin glycosides 16, 17 and 19, as well as trisaccharide 22, were synthesized. The acceptors 10 and 14 were subjected to DMTST‐mediated glucosylation for the synthesis of the chacotriose‐substituted compound 3. For a selective 2,4‐di‐rhamnosylation of the dihydrodiosgenin glucopyranoside, differentiation of the glucose OH groups was achieved by selective benzoylation with 1‐(benzoyloxy)benzotriazole. Reaction of the 3,6‐di‐O‐benzoate 32 with the perbenzoylated ethyl thiorhamnopyranoside donor 15 gave the 2,4‐di‐rhamnosylated compound 33, together with the mono‐rhamnosylated derivative. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)