- Decorated single-enantiomer phosphoramide-based silica/magnetic nanocomposites for direct enantioseparation
-
The nano-composites Fe3O4SiO2(-O3Si[(CH2)3NH])P(O)(NH-R(+)CH(CH3)(C6H5))2 (Fe3O4SiO2PTA(+)) and Fe3O4SiO2(-O3Si[(CH2)3NH])P(O)(NH-S(-)CH(CH3)(C6H5))2 (Fe3O4SiO2PTA(-)) were prepared and used for the chiral separation of five racemic mixtures (PTA = phosphoric triamide). The separation results show chiral recognition ability of these materials with respect to racemates belonging to different families of compounds (amine, acid, and amino-acid), which show their feasibility to be potential adsorbents in chiral separation. The nano-composites were characterized by FTIR, TEM, SEM, EDX, XRD, and VSM. The VSM curves of nano-composites indicate their superparamagnetic property, which is stable after their use in the separation process. Fe3O4, Fe3O4SiO2, Fe3O4SiO2PTA(+) and Fe3O4SiO2PTA(-) are regularly spherical with uniform shape and the average sizes of 17-20, 18-23, 36-47 and 43-52 nm, respectively.
- Karimi Ahmadabad, Fatemeh,Pourayoubi, Mehrdad,Bakhshi, Hadi
-
p. 27147 - 27156
(2019/09/12)
-
- Supramolecular metathesis: Co-former exchange in co-crystals of pyrazine with (R,R)-, (S,S)-, (R,S)- and (S,S/R,R)-tartaric acid
-
Co-crystals of dextro-(R,R), levo-(S,S), meso-(R,S) and racemic (R,R-S,S)-tartaric acid with pyrazine were obtained by manual kneading and slurry experiments; subsequent reactions in the solid state between these co-crystals and the various forms of tartaric acid in the solid state and via slurry show that co-former exchange takes place according to the sequence of stability [(R,S)-ta]2·py > (S,S/R,R)-ta·py > (R,R)-ta·py or (S,S)-ta·py.
- Braga, Dario,Grepioni, Fabrizia,Lampronti, Giulio I.
-
body text
p. 3122 - 3124
(2012/02/15)
-
- Plaster retarding composition
-
The present invention is related to a calcium tartrate plaster retarding composition, characterised in that it has a mean particle size lower than 30 μm,The present invention is also related to the plaster comprising said composition and to the preparation process of said composition.
- -
-
-
- The reaction of hyaluronic acid and its monomers, glucuronic acid and N- acetylglucosamine, with reactive oxygen species
-
Synovial fluid is a ~0.15% (w/v) aqueous solution of hyaluronic acid (HA), a polysaccharide consisting of alternating units of GlcA and GlcNAc. In synovial fluid of patients suffering from rheumatoid arthritis, HA is thought to be degraded either by radicals generated by Fenton chemistry (Fe2+/H2O2) or by NaOCl generated by myeloperoxidase. We investigated the course of model reactions of these two reactants in physiological buffer with HA, and with the corresponding monomers GlcA and GlcNAc. meso-Tartaric acid, arabinuronic acid, arabinaric acid and glucaric acid were identified by GC-MS as oxidation products of glucuronic acid. When GlcNAc was oxidised, erythronic acid, arabinonic acid, 2-acetamido-2-deoxy-gluconic acid, glyceric acid, erythrose and arabinose were formed. NaOCl oxidation of HA yielded meso-tartaric acid; in addition, arabinaric acid and glucaric acid were obtained by oxidation with Fe2+/H2O2. These results indicate that oxidative degradation of HA proceeds primarily at glucuronic acid residues. meso-Tartaric acid may be a useful biomarker of hyaluronate oxidation since it is produced by both NaOCl and Fenton chemistry.
- Jahn, Michael,Baynes, John W.,Spiteller, Gerhard
-
p. 228 - 234
(2007/10/03)
-
- Oxidation of methyl and n-octyl α-D-glucopyranoside over graphite-supported platinum catalysts: Effect of the alkyl substituent on activity and selectivity
-
The oxidation of methyl and n-octyl α-D-glucopyranoside to methyl and n-octyl α-D-glucopyranosiduronate with molecular oxygen over a graphite-supported platinum catalyst was investigated. An increase of the length of the n-alkyl substituent from methyl to n-octyl resulted in a ten-fold decrease of the catalyst activity and an increase of the selectivity at pH 8.0 and 323 K. The selectivity decreased with increasing pH. The lower activity for a longer n-alkyl substituent is attributed to steric effects upon adsorption on the platinum surface and not to internal diffusion limitations. A tentative reaction scheme is presented, which describes the formation of side products through oxidation of secondary hydroxyl groups, ring cleavage and hydrolysis. Major side products are mono- and di-carboxylates with 2, 4, and 6 carbon atoms and mono-carboxylates, resulting from the oxidation of the alkyl substituent. C-C-Bond cleavage mainly occurs between C-2 and C-3 or C-4 and C-5, the former being less important for a longer alkyl substituent. The higher selectivity for a longer alkyl substituent is attributed to its protecting ability against hydrolysis and the exposition of neighboring hydroxyl groups to the platinum surface.
- Vleeming, Johannes H.,Kuster, Ben F.M.,Marin, Guy B.
-
p. 175 - 183
(2007/10/03)
-
- 2H-naphth[2,3-b]-1,4-oxazine derivatives, their preparation and their use as serotonin 1D (5-HT1D) receptor agonists
-
Compounds of formula I wherein R?is (C1-4)alkyl, (C3-6)alkenyl, whereby the double bond is not in α-position to the nitrogen atom, or (C3-7)cycloalkyl(C1-2)alkyl,R?is (C1-4)alkoxy, (C2-6)alkenyloxy or (C3-7) cycloalkyl(C1-2)alkoxy, andR?is (C1-4)alkylcarbonyl, (C1-4) alkyl, α-hydroxy(C1-4)alkyl, (C2-5)alkenyl, (C1-4)alkoxy(C1-4) alkyl or (C3-7)cycloalkyl,in free base or acid addition salt form, exhibit serotonin 1D (5-HT?D)-receptor agonistic activity and are thus useful interalia in the treatment of migraine, depression, anxiety and pain.
- -
-
-
- Racemization of optically active tartaric acid
-
An optically active enantiomer of tartaric acid or a salt thereof is racemized by mixing meso-tartaric acid or a salt thereof with a solution of an optically active enantiomer of tartaric acid or a salt thereof in a molar ratio of 0.2 - 0.5 and thereafter heating the mixture.
- -
-
-
