Resolution of (±)‐β‐methylphenylethylamine by a novel chiral stationary phase for Pirkle‐type column chromatography

In this study, a new Pirkle‐type chiral column stationary phase for resolution of β‐methylphenylethyl amine was described by using activated Sepharose 4B as a matrix, L ‐tyrosine as a spacer arm, and an aromatic amine derivative of L ‐glutamic acid as a ligand. The binding capacities of the stationary phase were determined at different pH values (pH = 6, 7, and 8) using buffer solutions as mobile phase, and enantiomeric excess (ee) was determined by HPLC equipped with chiral column. The ee was found to be 47%. Chirality, 2010. © 2009 Wiley‐Liss, Inc.     

Disposition kinetics of ML-1035 sulfoxide enantiomers and the prochiral sulfide in rats

ML-1035, 4-amino-5-chloro-2-[2-(methylsulfinyl)ethoxy]-N-[2-(diethylamino)ethyl]benzamide, is a sulfoxide compound and a racemic gastroprokinetic agent with a chiral center at the sulfur atom. We have investigated the disposition kinetics of (R)-ML-1035 sulfoxide (R) and (S)-ML-1035 sulfoxide (S) after the single enantiomers and the racemic mixture were administered to rats in separate experiments. There was no noticeable chiral inversion after either enantiomer dose. Both enantiomers were rapidly absorbed. After dosing with enantiomers or with the racemate, the resulting plasma concentration-time curve of R was closely parallel to that of S in both intravenous and oral experiments, suggesting that the two enantiomers have approximately the same disposition kinetics. After intravenous enantiomer doses, only S underwent conversion to sulfide, suggesting that sulfidation in the liver is enantioselective. However, the enantioselective sulfidation after intravenous dosing did not introduce a difference in the global plasma disposition profiles between R and S, since the reduction reaction is a minor metabolic process. Other metabolic reactions such as sulfonation and mono-N-desethylations were not enantioselective. After oral administration, conversion to sulfide was observed for both enantioners, implicating the existence of a nonhepatic pathway in sulfidation. Administration of a prochiral sulfide dose was associated with an enantioselective sulfoxidation, in which the R/S concentration ratios increased as a function of time. In addition, enantiomeric interaction causing changes in pharmacokinetic parameters was observed after the oral racemate dose, while the interaction is negligible after an intravenous racemate dose, indicating a route dependency in enantiomeric interaction. © 1993 Wiley-Liss, Inc.     

Chiral asymmetry in spiral galaxies?

Spiral galaxies are chiral entities when coupled with the direction of their recession velocity. As viewed from the Earth, the S‐shaped and Z‐shaped spiral galaxies are two chiral forms. What is the nature of chiral symmetry in spiral galaxies? In the Carnegie Atlas of Galaxies that lists photographs of a total of 1,168 galaxies, we found 540 galaxies, classified as normal or barred spirals, that are clearly identifiable as S‐ or Z‐ type. The recession velocities for 538 of these galaxies could be obtained from this atlas and other sources. A statistical analysis of this sample reveals no overall asymmetry but there is a significant asymmetry in certain subclasses: dominance of S‐type galaxies in the Sb class of normal spiral galaxies and a dominance of Z‐type in the SBb class of barred spiral galaxies. Both S‐ and Z‐type galaxies seem to have similar velocity distribution, indicating no spatial segregation of the two chiral forms. Chirality 13:351–356, 2001. © 2001 Wiley‐Liss, Inc.     

The Ultuna long-term soil organic matter experiment

In 1991, soil samples were taken from the long-term (40 years old) field trial at Ultuna in order to investigate soil P status and the distribution of its various forms. Among the treatments investigated, two were inorganic PK additions only – one to continuous fallow (PK-fallow) and the other to cropped fields (PK). There were also treatments amended with PK in combination with applications of straw, green manure composed of grass (GM), farmyard manure (FYM) or sewage sludge (SS). A total of 720, 720, 883, 1154, 1941 and 6617 kg P h^-1 had been supplied in the PK-fallow, PK, Straw, GM, FYM and SS treatments, respectively up to 1991. The soil P distribution was determined by step-wise fractionation using anion exchange resin (resin-P), sodium bicarbonate (bicarb-P), sodium hydroxide (hyd-P), and HCl (HCl-P). Finally, the soil was digested to obtain residual P (resid-P). The amendments resulted in a significant (p=0.05) enrichment of total P in soils relative to the initial value. A breakdown of the bicarb-P and hyd-P into inorganic P (P_i) and organic P (P_o) was manifested as considerable transformations within these P compartments compared with the initial values. Thus, total P_i (resin-P, bicarb-P_i, hyd-P_i, HC1-P, resid-P)/total P_o (bicarb-P_o, hyd-P_o) ratios markedly decreased in all treatments relative to control. The two P compartments were significantly and negatively (p =0.05) correlated. On average, the total P_o increase was about 380 mg kg^-1 (range 270–715). The results suggested that an equilibrium between P_i immobilization and P_o mineralization was difficult to attain under any of the experimental management regimes used, which exclude inorganic N application. The balance sheet calculations revealed P deficits ranging from about 10 to 60 kg ha^-1, indicating that some P had migrated to the subsoil.     

垦殖对新疆绿洲农田土壤有机碳组分及团聚体稳定性的影响

土壤有机碳是土壤质量变化的重要指标,土壤活性有机碳组分在土壤质量变化方面发挥重要作用。采用有机碳分组技术,研究了干旱荒漠区自然土壤开垦对绿洲农田土壤有机碳活性组分及团聚体稳定性的影响。结果表明:低有机碳含量的自然土壤垦殖后,有利于干旱荒漠区绿洲棉田土壤有机碳的积累,且垦殖(0-5a)增加显著,年均增加在0.65gkg-1以上,上升幅度为76%-286%,5a后维持在相对平衡的水平;土壤活性有机碳、轻组有机碳在垦殖0-5a显著增加,平均增加72%和99%,5a后下降;颗粒有机碳则表现出垦殖0-10a明显增加,增加在275%以上,10a后下降;土壤水稳性团聚体含量随垦殖年限的延长显著增加,0-20a内较自然土壤提高了75%。垦殖可能是干旱区绿洲农田潜在碳汇的重要影响因素;但随垦殖年限延长,土壤有机碳活性组分下降,土壤质量又存在一定的退化风险。     

Functionalities tuned enantioselectivity of phenylcarbamate cyclodextrin clicked chiral stationary phases in HPLC

The mixed chloro‐ and methyl‐ functionalities can greatly modulate the enantioselectivities of phenylcarbamate cyclodextrin (CD) clicked chiral stationary phases (CSPs). A comparison study is herein reported for per(4‐chloro‐3‐methyl)phenylcarbamate and per(2‐chloro‐5‐methyl)phenylcarbamate β‐CD clicked CSPs (i.e., CCC4M3‐CSP and CCC2M5‐CSP). The enantioselectivity dependence on column temperature was studied in both normal‐phase and reversed‐phase mode high performance liquid chromatography (HPLC). The thermodynamic study revealed that the stronger intermolecular interactions can be formed between CCC4M3‐CSP and chiral solutes to drive the chiral separation. The higher enantioselectivities of CCC4M3‐CSP were further demonstrated with the enantioseparation of 17 model racemates in HPLC.     

Investigation of the enantioselectivity and enantiomeric elution order of some piperidine-2,6-dione drugs on chiralcel OD column

The enantioselectivity and enantiomeric separation of five racemic piperidine-2,6-dione compounds, on the cellulose tris(3,5-dimethylphenyl carbamate) chiral stationary phase Chiralcel OD-CSP were investigated under the same chromatographic conditions. This class of drugs includes glutethimide, aminoglutethimide, cyclohexylaminoglutethimide, pyridoglutethimide, and phenglutarimide. The results revealed that chiral recognition and the binding sites of these drugs on the Chiralcel OD column are similar, regardless of the absolute configuration of the individual enantiomers. A possible chiral recognition mechanism(s) for this class of drugs and the CSP is presented. © 1994 Wiley-Liss, Inc.     

Alcohol Induced Reversal of Enantioselectivity in a Lipase Catalyzed Resolution of 2-Chloropropionic Acid

Alcohol induced reversal of enantioselectivity in the esterification of 2-chloropropionic acid using lipase from Candida cylindracea has been investigated. It was found that an alcohol having substituents both at the α- and the β-carbon preferentially esterified the S-acid, while a straight chain alcohol preferentially esterified the R-acid. Intermediate enantioselectivities were obtained with alcohols having substituents either at the α- or the β-carbon, but still in favor of the R-acid. An acyl binding domain composed of three subsites is proposed for this lipase; one for the hydrocarbon chain, a second for a methyl substituent and a third for an electronegative substituent.     

Diastereoselective hydrogenations of unsymmetrically substituted aromatics

Attempts to induce enantioselectivity in the catalytic hydrogenation of unsymmetrically substituted aromatics using covalently bound, well known chiral auxiliaries are described. Marked differences in stereoselectivity and rate of hydrogenolysis are noted as a function of the auxiliary used. Enantioselectivities obtained in the resulting cyclohexyl derivatives are rather poor. © 1995 Wiley-Liss, Inc.