Search results for "Chiral"

Enantiospecific Brook Rearrangement of Tertiary Benzylic α-Hydroxysilanes

2018

The Brook rearrangement of simple, chiral tertiary benzylic -hydroxysilanes is presented. The rearrangement followed by proton trapping is enantiospecific and proceeds with inversion of the configuration at the carbon center. Importantly, the [1,2]-Brook rearrangement can be followed by trapping of methyl or allyl electrophiles even in the protic environment, although with minimal retention of chirality.

Adsorption Structures of Amino Acids on Calcite(104)

2015

Elucidating the interaction details of proteins with the most stable cleavage plane of calcite , namely calcite(104), is of great importance for understanding the physicochemical mechanisms behind biomineralisation. In this context, amino acids are generally believed to serve as suitable model molecules, as they constitute the basic building blocks of proteins. In this work, we present a non-contact atomic force microscopy (NC-AFM) investigation of the adsorption of five proteinogenic amino acids on calcite(104) under ultra-high vacuum (UHV) conditions. For studying the structures formed from comparatively large amino acids, enantiopure tryptophan, tyrosine and aspartic acid molecules are d…

Phase selection of calcium carbonate through the chirality of adsorbed amino acids.

2007

Catalytic Enantioselective Aza-Reformatsky Reaction with Cyclic Imines

2016

A catalytic highly enantioselective aza-Reformatsky reaction with cyclic aldimines and ketimines for the synthesis of chiral b-amino esters with good yields and excellent enantioselectivities is reported.Areadily available diaryl prolinol is used as a chiral ligand, ZnMe2 as a zinc source and ethyl iodoacetate as reagent in the presence of air atmosphere. The reaction with cyclic ketimines generates a quaternary stereocenter with excellent levels of enantioselectivity. Furthermore, five-membered N-sulfonyl ketimines were used as electrophiles with good enantiomeric excesses, under the optimized reaction conditions. Moreover, several chemical transformations were performed with the chiral b-…

Input of P, N-(phosphanyl, amino)-ferrocene hybrid derivatives in late transition metals catalysis

2018

International audience; Unequally functionalized ferrocenes give access to valuable hemilabile reactivity in catalytic reaction. We address the synthesis of hybrid (P, N)-ferrocenyl compounds for which recent catalytic breakthrough applications have been reported, transversely in late transition metals chemistry. Palladium, nickel, rhodium, iridium, and emerging iron and gold catalysis are illustrated from selected examples, which include CC bond formation from cross-coupling and polymerization, allylic substitution, cyanation, hydroformylation, CH arylation and silylation and hydrogenation reactions.

Selective Extraction and Efficient Binding in a Protic Solvent of Contact Ion Triplets by Using a Thiourea-Based Bis-Calix[6]arene Receptor

2013

We report a D3h-symmetric tail-to-tail bis-calix[6]thiourea 5 that displays two divergent cavities triply connected by thiourea linkages. This calix[6]tube was efficiently synthesized through a [1+1] macrocyclization reaction and characterized by X-ray diffraction analysis. The binding properties of this heterotritopic receptor were evaluated in a protic environment (i.e., CD3OD/CDCl3) through NMR studies. Thus, bis-calix[6]thiourea 5 exhibits a remarkable ability in the cooperative complexation of an anion sandwiched between two ammonium ions, a high selectivity for ammonium sulfate salts being observed. The anion is bound through multiple hydrogen-bonding interactions at the thiourea bind…

Multivariate optimization approach for chiral resolution of drugs using human serum albumin in affinity electrokinetic chromatography-partial filling…

2005

The enantiomeric resolution of chiral compounds using HSA by means of affinity EKC (AEKC)-partial filling technique is the result of a delicate balance between different experimental variables such as protein concentration, running pH (background electrophoretic buffer, protein and compound solutions) and protein solution plug length. In this paper multivariate optimization approaches for chiral separation of four basic drugs (alprenolol, oxprenolol, promethazine and propranolol) using HSA as chiral selector in AEKC-partial filling technique are studied. The experimental conditions to achieve maximum resolution are optimized using the Box-Behnken experimental design. Partial least squares a…

Rational enantioselective design of chiral heterobimetallic single-chain magnets: synthesis, crystal structures and magnetic properties of oxamato-br…

2011

A new series of neutral oxamato-bridged M(II)Cu(II) chiral chains of general formula [MCuL(x)(S)(m)(H(2)O)(n)]·aS·bH(2)O [L(1)=(M)-1,1'-binaphthalene-2,2'-bis(oxamate) with M=Mn (1a) and Co (1b); L(2)=(P)-1,1'-binaphthalene-2,2'-bis(oxamate) with M=Mn (2a) and Co (2b)] and the analogous racemic chains of formula [MCuL(3)(S)(m)(H(2)O)(n)]·aS·bH(2)O [L(3)=1,1'-binaphthalene-2,2'-bis(oxamate) with M=Mn (3a) and Co (3b)] have been prepared by reaction of the corresponding dianionic oxamatocopper(II) complex [Cu(L(x))](2-) with Mn(2+) or Co(2+) cations in either dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). Solid circular dichroism (CD) spectra of the bimetallic chain compounds were reco…

Ultra-sensitive chiral sensing and analysis from the nanoscale to the earth’s atmosphere

2020

Chirality plays an essential role in life and, therefore, in modem science. I’ll present novel technologies for ultra-sensitive, absolute, chiral sensing and analysis, in all phases, from the nanoscale to the earth’s atmosphere.

Chiral Polyisocyanates from an Azomonomer with a Very High Chiral Induction

2001

The synthesis of new chiral polyisocyanates is described. For this purpose a new chiral azobenzene containing monomer with the chiral center in α-position to the isocyanate group was synthesized. The anionic copolymerization was carried out in THF as solvent with potassium cyanide that was complexed by 18-crown-6 as initiator. This allowed a better control of the reaction and thereby the synthesis of polyisocyanates with a fairly low polydispersity. The copolymers show an extremely high transfer of chirality from the chiral side groups to the helical backbone in dilute solution. Copolymers with only 1.6 mol % of chiral side groups show nearly the full optical rotation and exist predominantl…