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121.
The association of a C3v-symmetrical calix[6]tris-amine with different concave tris-carboxylic acids of various degrees of flexibility has been explored by 1H NMR spectroscopy. In all cases, self-assembled structures directed by the selective inclusion of a neutral guest molecule were obtained, the more preorganized being stable in protic solvents. With a rigid C3-symmetrical cap, chiral guest recognition in the calixarene cavity resulted. A large tris-acidic partner gave a unique molecular ditopic receptor that is able to simultaneously accommodate two neutral molecules in two distinct hydrophobic cavities with different binding processes. 相似文献
122.
Perfluoromethyl Element Ligands. XXIX. Preparation and Spectroscopic Investigation of M(CO)4L2 Complexes (M ? Cr, Mo, W; L ? Me2PSMe, Me2PSeMe, (CF3)2PSMe, (CF3)2PSMe) The complexes M(CO)4L2 (see Inhaltsübersicht) have been prepared by the reaction of tetracarbonyl norbornadiene metal compounds M(CO)4NBD with L at room temperature or 35°C, respectively. The cis-complexes formed in the first step undergo rearrangement to trans-isomers at higher temperatures. New compounds have been characterized by analytical and spectroscopic (IR, NMR, MS) methods. 相似文献
123.
This review covers our extensive research activities in the area of fluorine containing phospha- and arsaalkenes as well as selenocarbonyls, which differ considerably in their properties and reactivities from their alkyl and aryl counterparts and thus contribute in a gratifying manner to the still growing field of unsaturated element-carbon compounds of 3rd and 4th row main group elements E. Of particular interest is the influence of the fluorine substituents and other small groups (OR, NR2) with either inductive and/or mesomeric effects on the polarity and reactivity of the EC bond. Addition reactions of proton acidic and hydridic polar HX reactants as well as [2+2], [3+2] and [4+2] cycloadditions have been thoroughly studied. The results obtained allow a classification of the EC systems within five different types, A to E, and prove a change from “normal” to “inverse” heteroalkenes in this sequence. The ligand properties of some derivatives have also been investigated in some detail. 相似文献
124.
125.
Dieter Seebach Laurent Schaeffer Franois Gessier Pascal Bindschdler Corinna Jger Delphine Josien Sascha Kopp Grald Lelais YogeshR. Mahajan Peter Micuch Radovan Sebesta BerndW. Schweizer 《Helvetica chimica acta》2003,86(6):1852-1861
Multigram amounts of suitably protected β2‐amino acids with 17 of the 20 proteinogenic side chains are prepared by diastereoselective reactions of Li, B, or Ti enolates of the corresponding 3‐acyl‐4‐isopropyl‐5,5‐diphenyloxazolidin‐2‐ones (acyl‐DIOZ; 1 ) with appropriate electrophiles (amidomethylation, hydroxyalkylation, (benzyloxycarbonyl)methylation) in yields of 55–90% and with diastereoselectivities of 80 to >97% (Scheme). The primary products 2 – 8 thus obtained are converted to protected β2‐amino acids by standard procedures (Table 1). Many of the DIOZ derivatives are highly crystalline compounds (31 X‐ray crystal structures in Table 2). The chiral auxiliary DIOZ, readily prepared in either enantiomeric form, is recovered with high yield. 相似文献
126.
Berger A Djukic JP Pfeffer M de Cian A Kyritsakas-Gruber N Lacour J Vial L 《Chemical communications (Cambridge, England)》2003,(5):658-659
In the presence of large amounts of [Me4N]Cl, the reaction of ortho-chloromercurated 2-[(eta6-phenyl)tricarbonylchromium]pyridine with mu-chloro cyclopalladated aromatic compounds yields a series of new heteroleptic heterodinuclear cis-(C--N)2Pd(II) complexes, which are valuable precursors of planar chiral cyclopalladated (eta6-arene)Cr(CO)3 complexes. 相似文献
127.
Laurent Chaloin Nicole Van Mau Frédéric Heitz Laurent Chiche Jean-Claude Talbot 《Colloids and surfaces. B, Biointerfaces》1998,10(6):389R-412
In order to elucidate the influence on the lipidic environment on the recognition process of its membrane associated receptor, the interactions of the vasoconstrictor peptide endothelin 1 with various phospholipids have been investigated using different lipidic model membranes: monolayers at constant surface pressure, vesicles and micelles. A monolayer study of ET1 adsorbed onto the water surface has shown that the C-terminus of the peptide points towards the aqueous phase. Penetration measurements into lipidic monolayers indicate that ET1 adsorbs to phospholipids with an orientation similar to that of the air–water interface and fluorescence measurements are in agreement with such an orientation of the peptide. This adsorption is selective for neutral phospholipids and indicates that the nature of the phospholipid headgroups is of major importance for the approach of the membrane associated receptor. 相似文献
128.
Alain Merschaert Laurent DelhayeJean-Paul Kestemont Willy BrionePieter Delbeke Vincent MancusoFreddy Napora Khalid DikerDaniel Giraud Michel Vanmarsenille 《Tetrahedron letters》2003,44(24):4531-4534
A stereoselective approach has been developed for the synthesis of cis- and trans-2-methyl-4-arylpiperidines from a common intermediate. The Ni-catalyzed hydrogenolysis of N-Boc-2-methyl-4-aryl-4-piperidinols, obtained by addition of organometallic reagents on N-Boc-2-methyl-4-piperidone, afforded the trans derivatives with up to 95% selectivity whereas the corresponding cis isomers were obtained in the presence of palladium catalysts. 相似文献
129.
Thierry Le Borgne Pierre Thury Michel Ephritikhine 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(1):m8-m9
The ligand 1,2,3,4‐tetramethyl‐5‐(2‐pyridyl)cyclopentadiene (cp*py) forms a dinuclear complex with UIV, i.e. di‐μ‐oxo‐bis{chloro(diethyl ether‐κO)[(η5,κN)‐1,2,3,4‐tetramethyl‐5‐(2‐pyridyl)cyclopentadienyl]uranium(IV)}, [U2Cl2O2(C14H16N)2(C4H10O)2], in which cp*py acts as a chelating ligand, being bound to the metal atom by the cyclopentadienyl unit and also by the N atom of the pyridyl ring. 相似文献
130.
Syntheses of new sulfinylcinnolines, quinoxalines, quinazolines and phtalazines have been investigated starting from the appropriate halogenobenzodiazine derivatives. The latter were converted in one step to the corresponding sulfanyl benzodiazines which upon oxidation with m-CPBA led to the corresponding sulfoxide derivatives of benzodiazines in moderate to good yields. In parallel to this study, an improved method for the synthesis of 2-methylsulfinylquinoxaline starting from 2-sulfanylquinoxaline is also described and in the quinazoline series a synthetic route has been developed to prepare 2-tert-butyl-5-phenylsulfinylquinazoline with satisfactory yield as well as 2-tert-butyl-5-tert-butylsulfinyl-4(3H)-quinazolinone and 2-tert-butyl-8-tert-butylsulfinyl-4(3H)-quinazolinone. 相似文献