Structure Of Dimethyl Sulfoxide Research Articles

Synthesis of ursodeoxycholic acid by electrochemical stereoselective reduction of 7-ketolithocholic acid in aprotic solvents

A novel method of producing ursodeoxycholic acid was developed through electrochemical stereoselective reduction of 7-ketolithocholic acid (7K-LCA) in a undivided electrolytic cell and aprotic solvents as electrolyte. Five aprotic solvents were investigated as electrolytes, the simple structure of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) were easily attacked by chloride ions and undergo nucleophilic reactions, resulting in no target reactions. The structure of hexamethylphosphoric triamide (HMPA) and 1,3-methyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone (DMPU) is relatively complex, but chloride ions can still attack them, and it was easier for 7K-LCA to directly undergo a reduction reaction under the action of electric current, because of the small steric hindrance of chenodeoxycholic acid (CDCA), 7K-LCA was stereoselectively reduced to CDCA. Due to the stable structure of the five-membered imidazole ring of 1,3-dimethyl-2-imidazolidinone (DMI), 7K-LCA undergoes two nucleophilic and a "Walden inversion", thereby stereoselective reduction of 7K-LCA to UDCA. In DMI, the highest conversion rate of 7K-LCA was 58.3%, the yield of UDCA was 34.9%, ee value was 100%. Linear sweep voltammetry was used to explore the electrochemical behavior of the reaction, and the electrolysis results were consistent with the linear sweep voltammetry. The product was characterized by using IR, 1H NMR and 13C NMR, it confirm the product was UDCA. The method developed in this paper provides a relatively environmentally friendly and low-consumption method for large-scale production of ursodeoxycholic acid, and provides a valuable reference for the asymmetric electrochemical reduction of ketone groups.

Local structure of dilute aqueous DMSO solutions, as seen from molecular dynamics simulations.

The information about the structure of dimethyl sulfoxide (DMSO)-water mixtures at relatively low DMSO mole fractions is an important step in order to understand their cryoprotective properties as well as the solvation process of proteins and amino acids. Classical MD simulations, using the potential model combination that best reproduces the free energy of mixing of these compounds, are used to analyze the local structure of DMSO-water mixtures at DMSO mole fractions below 0.2. Significant changes in the local structure of DMSO are observed around the DMSO mole fraction of 0.1. The array of evidence, based on the cluster and the metric and topological parameters of the Voronoi polyhedra distributions, indicates that these changes are associated with the simultaneous increase of the number of DMSO-water and decrease of water-water hydrogen bonds with increasing DMSO concentration. The inversion between the dominance of these two types of H-bonds occurs around XDMSO = 0.1, above which the DMSO-DMSO interactions also start playing an important role. In other words, below the DMSO mole fraction of 0.1, DMSO molecules are mainly solvated by water molecules, while above it, their solvation shell consists of a mixture of water and DMSO. The trigonal, tetrahedral, and trigonal bipyramidal distributions of water shift to lower corresponding order parameter values indicating the loosening of these orientations. Adding DMSO does not affect the hydrogen bonding between a reference water molecule and its first neighbor hydrogen bonded water molecules, while it increases the bent hydrogen bond geometry involving the second ones. The close-packed local structure of the third, fourth, and fifth water neighbors also is reinforced. In accordance with previous theoretical and experimental data, the hydrogen bonding between water and the first, the second, and the third DMSO neighbors is stronger than that with its corresponding water neighbors. At a given DMSO mole fraction, the behavior of the intensity of the high orientational order parameter values indicates that water molecules are more ordered in the vicinity of the hydrophilic group while their structure is close-packed near the hydrophobic group of DMSO.

Strategic Construction of Chiral Helices: Expanded Poly(l-leucine) Containing p-Phenylene Moieties

A series of expanded oligo- and poly(l-leucine)s, with an alternating arrangement of p-phenylene moieties and l-leucine residues, were synthesized by stepwise elongation or polycondensation and characterized by 1H NMR, SEC, ESI-MS, UV, and CD spectra. The degree of polymerization was found to be about 19 by SEC. Each monomer unit, i.e., expanded l-leucine, behaved like a chiral unit with a rigid bend body. Elongation of the peptide chain significantly increased the CD intensity per phenylene chromophore; however, the CD intensity decreased at high temperatures. This cooperative behavior strongly suggested the formation of a secondary structure. 1H NMR analysis revealed a right-handed helical structure in dimethyl sulfoxide. The theoretical calculations were consistent with these results.

Synthesis of monolithic columns based on poly(styrene-co-divinylbenzene) with the capillary-like flow-through pore diameter by template method

Poly(styrene-co-divinylbenzene) (PSt-DVB) is one of the most important kinds of organic polymeric monolithic columns. In order to improve its efficiency, it is necessary that the column has regular microstructure. In this research, hollow and ordered PSt-DVB columns were successfully prepared through radical polymerization using crystal structure of dimethyl sulfoxide as template. Different initiation types, times and storing temperatures were mainly investigated. The results showed PSt-DVB prepared at a temperature lower than the melting point of DMSO had regular and oriented structure. And longer initiating time and higher storing temperature helped polymer forming.

Investigations on the structure of dimethyl sulfoxide and acetone in aqueous solution

Aqueous solutions of dimethyl sulfoxide (DMSO) and acetone have been investigated using neutron diffraction augmented with isotopic substitution and empirical potential structure refinement computer simulations. Each solute has been measured at two concentrations-1:20 and 1:2 solute:water mole ratios. At both concentrations for each solute, the tetrahedral hydrogen bonding network of water is largely unperturbed, though the total water molecule coordination number is reduced in the higher 1:2 concentrations. With higher concentrations of acetone, water tends to segregate into clusters, while in higher concentrations of DMSO the present study reconfirms that the structure of the liquid is dominated by DMSO-water interactions. This result may have implications for the highly nonideal behavior observed in the thermodynamic functions for 1:2 DMSO-water solutions.

A Study on the β-Elimination Reaction from N-[2-(p-nitrophenyl)ethyl]quinuclidinium and 2-(p-nitrophenyl)ethyl bromide induced by amines in dimethylsulfoxide with formation ofp-nitrostyrene

Second order rate constants kEM−1s−1for the β-elimination reaction from N-[2-( p-nitrophenyl)ethyl]quinuclidinium and 2-( p-nitrophenyl)ethyl bromide induced by amines of different structure in dimethylsulfoxide at 50 °C have been measured. Application of the Brønsted equation shows a similar behaviour of the two substrates, with values of β = 0.649 and 0.584 respectively.

Structural chemistry and solvent properties of dimethylsulfoxide

An examination of the chemical environment and structure of dimethylsulfoxide (DMSO) in the solid state leads to a description of its bonding properties that is useful in proposing structures for solvation complexes in DMSO solutions. The O atom acts as a type A (hard) Lewis base of strength similar to or somewhat greater than that of water and is capable of bonding to metal cations with oxidation states between+1 and+3. The methylprotons are weakly acid and are found to form bonds to weak bases such as ClO 4 − , NO 3 − , and halogen ions. DMSO is an ideal solvent for compounds of strongly acid cations and weakly basic anions. Bonding alos occurs through S to type-B (soft) Lewis acids (groups 8–10) particularly when the soft Lewis acid is already coordinated to electron donor groups. In these cases the oxygen basicity is dependent on the electron donating or withdrawing power of the type-B acid.

Preferential conformation of substance P in solution

The three-dimensional structure of substance P has been studied by 1H-NMR, (500 MHz), and by circular dichroism (CD) in different solvents. The analysis of the different NMR parameters suggest that substance P adopts a rather extended structure in dimethylsulfoxide and pyridine. In water, besides the aggregation phenomenon, the monomeric substance P presents a complex conformational equilibrium. The addition of sodium dodecylsulfate to the aqueous solution induces, as shown by CD spectroscopy, a preferential alpha-helical conformation. And in methanol three structural conclusions may be drawn: the flexibility of the N-terminal Arg-Pro-Lys, the alpha-helical structure of Pro4-Gln5-Gln6-Phe7-Phe8 and the interaction of the C-terminal carboxamide with the primary amides from both glutamines.

Nuclear magnetic resonance study of fibrinogen-like peptides and their structure in dimethyl sulfoxide and water

The 1H nuclear magnetic resonance (NMR) spectra of four fibrinogen-like oligopeptides (H-Gly-Pro-Ala-NH2, H-Arg-Gly-Pro-Ala-NH2, H-Val-Arg-Gly-Pro-Ala-NH2, and H-Gly-Val-Arg-Gly-Pro-Ala-NH2) in dimethyl-d6 sulfoxide (Me2SO-d6), and of the hexapeptide in water, and the 13C NMR spectrum of H-Gly-Pro-Ala-NH2 in Me2SO-d6, were recorded and interpreted in terms of preferred conformations in solution. Each peptide exists in Me2SO-d6 as in a 30:70 mixture of cis and trans isomers about the Gly-Pro bond, and the hexapeptide in water is solely the trans isomer. For the trans isomers in Me2SO-d6, there is a hydrogen bond between the Gly CO group and one of the C-terminal primary amide hydrogens, and a beta turn involving the Gly-Pro-Ala-NH, section of the molecules. A strong NOE between Pro CalphaH and Ala NH for the trans isomer of the tripeptide in Me2SO-d6 completes the identification of this structural feature as a type II beta turn.

The solvent dimethyl sulfoxide.

AbstractThe dipolar aprotic solvent dimethyl sulfoxide is liquid over a wide range of temperatures, is a strong electron donor, and has a high polarity. It is therefore an excellent and selective solvent for many organic and even polymeric compounds, and can enter into H‐bonding and dipole‐dipole association. The structure of dimethyl sulfoxide, with a “hard” oxygen atom and a “soft” sulfur atom, leads to good solvation of cations and poor solvation of anions. Mixtures of alkoxides with dimethyl sulfoxide are therefore among the most strongly basic systems in organic chemistry, and are excellently suited for the deprotonation of weakly acidic OH, NH, and CH bonds, for eliminations, and for the initiation of polymerizations.