Nematic ordering of model racemic mixture of stiff trimer chains

In Italy, at the end of the 1970s, methadone hydrochloride was introduced for the treatment of opioid use disorder, in the form of a racemic mixture consisting of levomethadone and dextromethadone.In 2015 Levometadone was introduced, a new formulation marketed in Italy for the treatment of opioid use disorder in 2015.The article aims to bring the experience of an Italian Addiction Centre back to the use of this new formulation in the "real life" analyzing the efficacy, the trend of adverse events and pharmacological iterations in a context in which the treated population often uses besides the opiates, cocaine and alcohol, are burdened by a relevant physical and psychic comorbidity and frequently have a prescribed polypharmacy.

Download Full-text

Conversion of fructose into methyl lactate over SnO2/Al2O3 catalystin flow regime

Catalysis and petrochemistry ◽

10.15407/kataliz2020.30.043 ◽

2020 ◽

pp. 43-47

Author(s):

S.V. Prudius ◽

◽

N.L. Hes ◽

A.M. Mylin ◽

V.V. Brei ◽

...

Keyword(s):

Flow Reactor ◽

Practical Interest ◽

Dimethyl Acetal ◽

Racemic Mixture ◽

Process Conditions ◽

Impregnation Method ◽

Aqueous Methanol ◽

Methyl Lactate ◽

Al2o3 Catalyst ◽

Target Reaction

In recent years, numerous researchers have focused on the development of catalytic methods for processing of biomass-derived sugars into alkyl lactates, which are widely used as non-toxic solvents and are the starting material for obtaining monomeric lactide. In this work, the transformation of fructose into methyl lactate on Sn-containing catalyst in the flow reactor that may be of practical interest was studied. The supported Sn-containing catalyst was ob-tained by a simple impregnation method of granular γ-Al2O3. The catalytic ex-periments were performed in a flow reactor at temperatures of 160-190 °C and pressure of 3.0 MPa. The 1.6-9.5 wt.% fructose solutions in 80% aqueous methanol were used as a reaction mixture. It was found that addition to a reac-tion mixture of 0.03 wt.% potassium carbonate leads to the increase in selec-tivity towards methyl lactate on 15% at 100% conversion of fructose. Prod-ucts of the target reaction С6Н12О6 + 2СН3ОН = 2С4Н8О3 + 2Н2О were ana-lyzed using 13C NMR method. The following process conditions for obtaining of 65 mol% methyl lactate yield at 100% fructose conversion were found: use of 4.8 wt.% fructose solution in 80% methanol, 180 °С, 3.0 МПа and a load on catalyst 1.5 mmol C6H12O6/mlcat/h at contact time of 11 minutes. The cata-lyst productivity is 2.0 mmol C4H8O3/mlcat/h and the by-productі are 1,3-dihydroxyacetone dimethyl acetal (20%) and 5-hydroxymethylfurfural (10%). It should be noted that a racemic mixture of L- and D-methyl lactates has been obtained by conversion of D-fructose on the SnO2/Al2O3 catalyst. The SnO2/Al2O3 catalyst was found to be stable for 6 h while maintaining full fruc-tose conversion at 55–70% methyl lactate selectivity. After regeneration the catalyst completely restores the initial activity.

Download Full-text

Structural similarity in chiral-achiral multi-component crystals

CrystEngComm ◽

10.1039/d0ce00301h ◽

2020 ◽

Vol 22 (43) ◽

pp. 7334-7340 ◽

Cited By ~ 1

Author(s):

Ian J. Scowen ◽

Taghrid S. Alomar ◽

Tasnim Munshi ◽

Colin C. Seaton

Keyword(s):

Structural Similarity ◽

Racemic Mixture

Understanding the structural similarities between co-crystals formed with racemic mixture and enantiopure chiral components with an achiral co-former.

Download Full-text

Nematic ordering and defects on the surface of a sphere: A Monte Carlo simulation study

The Journal of Chemical Physics ◽

10.1063/1.2890724 ◽

2008 ◽

Vol 128 (10) ◽

pp. 104707 ◽

Cited By ~ 45

Author(s):

Martin A. Bates

Keyword(s):

Monte Carlo Simulation ◽

Monte Carlo ◽

Simulation Study ◽

Monte Carlo Simulation Study ◽

Nematic Ordering

Download Full-text

Tetrahydroberberine, a pharmacologically active naturally occurring alkaloid

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229615004076 ◽

2015 ◽

Vol 71 (4) ◽

pp. 262-265 ◽

Cited By ~ 14

Author(s):

Subramanya Pingali ◽

James P. Donahue ◽

Florastina Payton-Stewart

Keyword(s):

Hydrogen Bonds ◽

Crystal Packing ◽

Racemic Mixture ◽

Inversion Center ◽

Intermolecular Hydrogen Bonds ◽

Naturally Occurring ◽

Pharmacologically Active

Tetrahydroberberine (systematic name: 9,10-dimethoxy-5,8,13,13a-tetrahydro-6H-benzo[g][1,3]benzodioxolo[5,6-a]quinolizine), C20H21NO4, a widely distributed naturally occurring alkaloid, has been crystallized as a racemic mixture about an inversion center. A bent conformation of the molecule is observed, with an angle of 24.72 (5)° between the arene rings at the two ends of the reduced quinolizinium core. The intermolecular hydrogen bonds that play an apparent role in crystal packing are 1,3-benzodioxole –CH2...OCH3and –OCH3...OCH3interactions between neighboring molecules.

Download Full-text

Resolution of racemic mixture of α-amino acid derivative through composite membrane

Journal of Membrane Science ◽

10.1016/j.memsci.2011.05.049 ◽

2011 ◽

Vol 378 (1-2) ◽

pp. 531-540 ◽

Cited By ~ 27

Author(s):

Kripal Singh ◽

Pravin G. Ingole ◽

Jayesh Chaudhari ◽

Harshad Bhrambhatt ◽

Amit Bhattacharya ◽

...

Keyword(s):

Amino Acid ◽

Acid Derivative ◽

Composite Membrane ◽

Amino Acid Derivative ◽

Racemic Mixture

Download Full-text

Unfolding of Helical Poly(L-Glutamic Acid) in N,N-Dimethylformamide Probed by Pyrene Excimer Fluorescence (PEF)

Polymers ◽

10.3390/polym13111690 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1690

Author(s):

Weize Yuan ◽

Remi Casier ◽

Jean Duhamel

Keyword(s):

Glutamic Acid ◽

Local Density ◽

Guanidine Hydrochloride ◽

Racemic Mixture ◽

Excimer Fluorescence ◽

Excimer Formation ◽

Blob Model ◽

Α Helix ◽

The Relationship ◽

Pyrene Excimer Formation

The denaturation undergone by α–helical poly(L-glutamic acid) (PLGA) in N,N-dimethylformamide upon addition of guanidine hydrochloride (GdHCl) was characterized by comparing the fluorescence of a series of PLGA constructs randomly labeled with the dye pyrene (Py-PLGA) to that of a series of Py-PDLGA samples prepared from a racemic mixture of D,L-glutamic acid. The process of pyrene excimer formation (PEF) was taken advantage of to probe changes in the conformation of α–helical Py-PLGA. Fluorescence Blob Model (FBM) analysis of the fluorescence decays of the Py-PLGA and Py-PDLGA constructs yielded the average number (<Nblob>) of glutamic acids located inside a blob, which represented the volume probed by an excited pyrenyl label. <Nblob> remained constant for randomly coiled Py-PDLGA but decreased from ~20 to ~10 glutamic acids for the Py-PLGA samples as GdHCl was added to the solution. The decrease in <Nblob> reflected the decrease in the local density of PLGA as the α–helix unraveled in solution. The changes in <Nblob> with GdHCl concentration was used to determine the change in Gibbs energy required to denature the PLGA α–helix in DMF. The relationship between <Nblob> and the local density of macromolecules can now be applied to characterize the conformation of macromolecules in solution.

Download Full-text

Chiral Molecular Cavities of Calix[4]Crown on Au(111)

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2008.231 ◽

2008 ◽

Vol 8 (11) ◽

pp. 5702-5707 ◽

Cited By ~ 1

Author(s):

Ge-Bo Pan ◽

Jun Luo ◽

Qi-Yu Zheng ◽

Li-Jun Wan

Keyword(s):

Self Assembly ◽

Chiral Recognition ◽

Scanning Tunneling ◽

Racemic Mixture ◽

Tunneling Microscopy ◽

Geometrical Structures ◽

Simple Method ◽

Ordered Structures ◽

Ordered Arrays ◽

Stm Images

Well-ordered arrays of chiral molecular cavities have been constructed by self-assembly of inherently chiral calix[4]crown on Au(111) in 0.1 M HClO4 solution and investigated by scanning tunneling microscopy (STM). The chiral features are clearly observed in high resolution STM images. It is found that the adsorption of the two enantiomers results in the same ordered structures with upright orientation on Au(111). Moreover, only phase separation has been observed for the racemic mixture of the two enantiomers in the experiment. This is mainly due to the weak molecule-substrate interaction as well as asymmetric geometrical structures of the two enantiomers. The present study provides a simple method for construction of ordered arrays of chiral molecular cavities, which are of potential in chemical sensors, chiral recognition, and nonlinear optics.

Download Full-text