摘要:

AbstractThe rigid bowl‐shaped molecule cyclotriveratrylene (CTV,1) was provided with short and long spacer arms terminating in triphenyl phosphite functions. These CTV ligands were used to immobilize a rhodium(I)‐carbonyl‐hydride complex. The ligand with short spacers gave a rigid, strained complex with a trigonal‐coordination sphere around the rhodium. The ligand with long flexible spacers allowed the formation of a large cavity after the complexation to the rhodium center. This cavity, however, is filled up by the spacer arms, as was indicated by NMR studies. Variable‐temperature NMR experiments suggested that the H‐Rh‐CO dipole in the rhodium‐ CTV complex can adopt two orientations: one with the hydride group pointing away from the CTV cavity (low‐temperature conformation) and one in which this orientation is inverted (high‐temper

ISSN:0165-0513    

DOI:10.1002/recl.19951140902

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractMolecular‐mechanics (MM) and molecular‐dynamics (MD) simulations (in MeOH) were performed on Eu3+complexes of two derivatized calix[4]arenes (2band2d) and a bislariat diazacrown ether (3). The Quanta/CHARMm Lennard‐Jones parameters of Ca2+proved suitable as a model for the Lennard‐Jones parameters of Eu3+. The radial distribution function (RDF) of Eu3+… MeOH (O) agrees well with experimental data. The MD of2b· Eu3+showed that the phenolic oxygens cannot compete with the solvent, although they are preorganized. Three molecules of MeOH are within the first coordination shell. The MD of2d· Eu3+showed two transitions. After the first the Eu3+was coordinated by one molecule of MeOH and after the second by three molecules of MeOH. The pyridine ring was not involved in coordination to Eu3+, which explained the measured lifetimes and derived coordination shells in methanol. The calculations on3· Eu3+revealed that the conformation with the pendant arms in ananticonfiguration is unlikely to exist in solution, whereas thesynform calculated by MM rearranged to a structure with two molecules of MeOH in the first coordination sphere. This is consistent with experimental data, which show that the two dominant species in methanol solution have two molecules of MeOH coordinated to the Eu3+. All calculations were performed with the Quanta/CH

ISSN:0165-0513    

DOI:10.1002/recl.19951140903

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractCrystals of azocyclopropaneN,N′‐dioxide, (C3H5NO)2, (1) are monoclinic, space group C2/c,a= 8.708(2),b= 8.321(1),c= 9.836(2) Å, β = 95.437(3)° (243K). Z = 4. The finalRfor 479 independent observed reflections is 0.035. The molecules are centrosymmetric and have the bisecting (s‐cis) conformation for the NO group.Crystals of 1,1′‐dimethylazocyclopropaneN,N′‐dioxide, (C4H7NO)2, (2) are monoclinic, space groupP21/n, a= 10.727(5),b= 7.181(3),c= 5.969(2) Å, β = 90.52 (2)° (223K),Z= 2. The finalRfor 773 independent observed reflections is 0.046. The molecules are also centrosymmetric but steric interference by the methyl group at C1 prevents them from assuming the bisecting conformation. The effect of the N(O)N(R) group on the geometry of the cyclopropane ring is s

ISSN:0165-0513    

DOI:10.1002/recl.19951140904

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIodonium‐ion‐assisted condensation of methyl 4,7,8,9‐tetra‐O‐acetyl‐N‐acetyl‐2‐O‐[3‐ (methylthiomethoxy)propyl]‐α‐D‐neuraminate (15) with hexyl 2‐acetamido‐6‐O‐benzyl‐3‐O‐(tri‐O‐ benzyl‐α‐L‐fucopyranosyl)‐2‐deoxy‐β‐D‐glucopyranoside (12) furnished, after deprotection, SLexmimic3. The non‐fucosylated derivative2was obtained in a similar fashion by the coupling of15with hexyl

ISSN:0165-0513    

DOI:10.1002/recl.19951140905

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe synthesis and spectroscopic characterization of two retinal analogues is described, the paramagnetic 3‐pyrrolin‐1‐yloxy analogue1and its diamagnetic equivalent, the 3‐pyrroline analogue2.Various aspects of the synthesis of the aminoxy group containing polyenes are discussed. Upon interaction with bacterioopsin, both1and2are incorporated in the protein and form a system with λmax459 nm. Neither of the two bacteriorhodopsin analogues is photoactive. ESR spectroscopy data of the system containing1show that the ring part of the chromophore in the protein is rigidly fixed in ori

ISSN:0165-0513    

DOI:10.1002/recl.19951140906

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractSulfonations of the 1‐(trimethylsilyl)alk‐2‐enes1a‐12a, the 1‐(trimethylsilyl)‐ω‐phenyl‐alk‐2‐enes13a–18a, the triisopropylsilylalk‐2‐enes19a–21a, 1‐(trimethylsilyl)penta‐2,4‐diene (22a), and the allylsilane23awith sulfur trioxide were studied in the temperature range ‐60 to 25°C using dichloromethane‐d2as solvent and 1.5 mol‐equiv. of dioxane‐d8relative to the amount of SO3as reactivity moderator. For comparison, the sulfonation of the all carbon analogues24a–27awere also studied. Reaction of the 1‐(trialkylsilyl)alk‐2‐enes1a–11aand13a–17awith SO3at −60°C all afford the corresponding trialkylsilyl‐alk‐1‐ene‐3‐sulfonate esters c within 20 min in yields of>95%. 1‐(Trimethylsilyl)‐2‐cycloheptylideneethane (12a) at −60°C gives a mixture of the trimethylsilyl sulfonate ester12cand the isomeric 1‐(trimethylsilyl)‐2‐(1‐cycloheptenyl)ethane‐2‐sulfonic acid (12f) in a molar ratio of 4:6. With 1‐(trimethylsilyl)‐2‐(1,2,3,4‐tetrahydro‐1‐naphthylidene)‐ ethane (18a) the exclusive product is 1‐(trimethylsilyl)‐2‐(3,4‐dihydro‐1‐naphthyl)ethane‐2‐sulfonic acid (18f). Direct NMR evidence for the formation of β‐sultones as initial intermediates was observed in the sulfonation of the 1‐(trimethylsilyl)‐2‐cycloalkylideneethanes11aand12a.Upon sulfonation of the 1‐(triisopropylsilyl)‐alk‐2‐enes19a–21aat — 60°C the initial products are the β‐sultone20b‐IIand the carbyl sulfates19h‐IIand21h–II, of which the relative yields depend on the amount of SO3employed. The SO3sulfonation of 1‐(trimethylsilyl)penta‐2,4‐diene (22a) gives trimethylsilyl penta‐1,3‐diene‐5‐sulfonate (22i). The three homologous non‐silicon containing 1‐ cycloalkylidenehexanes24a–26aat — 60°C afford the respective 1‐cycloalkylhexane‐1,1′‐sultones24b‐III–26b‐IIIwhich, at higher temperatures, isomerize to give the 1‐(cycloalk‐1′‐enyl)hexane‐1‐ sulfonic acids24m–26m.1‐Methylene‐1,2,3,4‐tetrahydronaphthalene (27a) reacts with SO3at −60°C to give (3,4‐dihydro‐1‐naphthyl)methanesulfonic acid (27o). Treatment of the various products containing a trialkylsilyl sulfo

ISSN:0165-0513    

DOI:10.1002/recl.19951140907

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper describes the first example of complex formation of an alkylglycoside with calcium ions. Qualitative evidence for complex formation is obtained by titration microcalorimetry.

ISSN:0165-0513    

DOI:10.1002/recl.19951140908

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19951140910

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19951140901

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY