Dérivés diglycosyliques. Communication préliminaire

Diglycosyl Derivatives. Preliminary communication Novel types of diglycosyl compounds, some of them bearing a resemblance to natural di- or tri-saccharides are described: a diglycosyldiyne ( 1 ), a diglycosylthiophene ( 2 ), a diglycosylaziridine ( 3 ), a diglycosyldioxolane ( 4 ), as well as six C,N-diglycosylnitrones, 9b–9f and 14 . These C,N-diglycosylnitrones, on treatment with an acetylenic Grignard reagent, led to the expected acetylenic diglycosyl-hydroxylamine 11 , whereas diglycosylisoxazolines (f. ex. 10 ) were obtained when these nitrones underwent 1,3-dipolar cycloaddition to acetylenic compounds.     

Synthesis of a chiral calixarene: 5,11,17,23-tetra (tert-butyl)-25,27-bis[((+)-camphor-10-sulfonyl)-oxy]-calix[4]arene-26,28-diol: crystal and molecular structure of its (1∶2) complex with toluene

The title compound was obtained by treatment ofp-tert-butylcalix[4]arene with (+) camphorsulfonyl chloride in triethylamine and toluene. A (12) complex with toluene has been found. Its structure has been determined by X-ray crystallography. Crystals are triclinic with space group P1,a=16.426(3),b=18.553(3),c=13.661(2) Å, =94.78(2), =110.76(2), =72.83(2)°,V=3720(2) ų,d _c =1.127 g/cm³ Z=2. Refinement based on 10495 observed reflections led to a finalR value of 0.100. The two independent molecules of calixarene in the asymmetric unit are in the cone conformation and the calixarene cavities are empty. The guest molecule occupies the interhost space. The norborane skelton of (+) camphorsulfonyl group is the same as ones found in literature. Only van der Waals interactions exist between the host and the guest molecules.     

Positivity certificates and polynomial optimization on non-compact semialgebraic sets

Mathematical Programming - In the classic maximum coverage problem, we are given subsets $$T_1, \ldots , T_m$$ of a universe [n] along with an integer k and the objective is to find a subset $$S...     

Conjugation properties of tensor product and fusion coefficients

We review some recent results on properties of tensor product and fusion coefficients under complex conjugation of one of the factors. Some of these results have been proven, some others are conjectures awaiting a proof, one of them involving hitherto unnoticed observations on ordinary representation theory of finite simple groups of Lie type.     

Preparation and Thermal Properties of N-Alkylidene-Ethenesulfenamides

A convenient preparation of N,N-bis(trimethylsilyl)-ethenesulfenamides is describe, together with its fluoride-catalysed reaction with aldehydes or ketones to provide several N-alkylidene-ethenesulfenamides. On mild heating, two of these S-vinylthiooximes can be converted into the corresponding substituted pyrroles.     

Langmuir monolayers of an inclusion complex formed by a new calixarene derivative and fullerene

The design of new molecules with directed interactions to functional molecules as complementary building blocks is one of the main goals of supramolecular chemistry. A new p-tert-butylcalix[6]arene monosubstituted derivative bearing only one alkyl chain with an acid group (C6A3C) has been synthesized. The C6A3C has been successfully used for building Langmuir monolayers at the air-water interface. The C6A3C molecule adopts a flatlike orientation with respect to the air-water interface. The molecular structure gives the molecule amphiphilic character, while allowing the control of both the dissociation degree and the molecular conformation at the air-water interface. The C63AC has been combined with pristine fullerene (C60) to form the supramolecular complex C6A3C:C60 in 2:1 molar ratio (CFC). The CFC complex retains the ability of C6A3C to form Langmuir monolayers at the air/water interface. The interfacial molecular arrangement of the CFC complex has been convincingly described by in situ UV-vis reflection spectroscopy and synchrotron X-ray reflectivity measurements. Computer simulations complement the experimental data, confirming a perpendicular orientation of the calixarene units of CFC with respect to the air-water interface. This orientation is stabilized by the formation of intermolecular H-bonds. The interfacial monolayer of the CFC supramolecular complex is proposed as a useful model for the well-defined self-assembly of recognition and functional building blocks.     

Cu(I) and Zn(II) chelations on polymer beads modified by attachment of a bipyridyl-calixarene-based chelate

A new chelating calix[4]arene derivative incorporating two bipyridyl groups and one primary amino attachment function at the lower rim has been synthesised and coupled to Wang benzaldehyde resin. The new material effectively displayed complexation abilities towards Cu(I) and Zn(II) transition metal cations. The grafting efficiency was evaluated and quantified by complexation experiments, using UV/visible spectrophotometry, and ionic chromatography.     

A concise synthesis of 2,5-dideoxy-2,5-imino-d-mannitol (DMDP) and HomoDMDP from l-xylose

A short and practical procedure for the preparation of C-2 substituted polyhydroxypyrrolidines is described. The C-2 substituent is introduced by a stereoselective addition of a Grignard reagent to a 2,3,5-protected aldofuranose and the cyclization to the pyrrolidine ring system is performed through a bis-mesylation/double nucleophilic displacement sequence. The efficiency of the methodology was demonstrated by its application to the synthesis of HomoDMDP and DMDP.