scholarly journals Enantiomeric Tartaric Acid Production Using cis-Epoxysuccinate Hydrolase: History and Perspectives

Molecules ◽  
2019 ◽  
Vol 24 (5) ◽  
pp. 903 ◽  
Author(s):  
Jinsong Xuan ◽  
Yingang Feng
Keyword(s):  
Tartaric Acid ◽  
Acid Production ◽  
Enantiomeric Excess ◽  
Enantiomeric Purity ◽  
Enantioselective Synthesis ◽  
Future Research ◽  
Tartaric Acids ◽  
Catalytic Mechanisms ◽  
Very High ◽  
Hydrophilic Molecule

Tartaric acid is an important chiral chemical building block with broad industrial and scientific applications. The enantioselective synthesis of l(+)- and d(−)-tartaric acids has been successfully achieved using bacteria presenting cis-epoxysuccinate hydrolase (CESH) activity, while the catalytic mechanisms of CESHs were not elucidated clearly until very recently. As biocatalysts, CESHs are unique epoxide hydrolases because their substrate is a small, mirror-symmetric, highly hydrophilic molecule, and their products show very high enantiomeric purity with nearly 100% enantiomeric excess. In this paper, we review over forty years of the history, process and mechanism studies of CESHs as well as our perspective on the future research and applications of CESH in enantiomeric tartaric acid production.

Enantioselective synthesis of isoquinoline alkaloids: phenylethylisoquinoline and aporphine alkaloids

1987 ◽  
Vol 65 (10) ◽  
pp. 2356-2361 ◽  
Author(s):  
Zbigniew Czarnocki ◽  
David B. MacLean ◽  
Walter A. Szarek
Keyword(s):  
Asymmetric Synthesis ◽  
Tartaric Acid ◽  
Enantiomeric Purity ◽  
Enantioselective Synthesis ◽  
Isoquinoline Alkaloids ◽  
Aporphine Alkaloid ◽  
Ring Systems

A new and improved procedure for the preparation of (R)-2-alkoxycarbonyl-1-formyl-1,2,3,4-tetrahydro-6,7-dimethoxyisoquinolines has been developed beginning from D-(−)-tartaric acid. The utility of these aldehydes in the asymmetric synthesis of isoquinoline alkaloids of high enantiomeric purity has been extended to the synthesis of phenylethylisoquinolines, which have been further transformed in straightforward steps into the homoprotoberberine and homoaporphine ring systems. In this manner, (S)-homolaudanosine, (S)-5′-methoxyhomolaudanosine, (S)-2,3,9,10,11-pentamethoxyhomoprotoberberine, and (S)-O-methylkreysigine have been synthesized. The conversion of (S)-laudanosine to (S)-glaucine, an aporphine alkaloid, has also been realized.

Enzymatic Iodination of Maleic and Fumaric Acids Diethyl Esters

2009 ◽  
Vol 59 (12) ◽  
pp. 1400-1404
Author(s):  
Marius Tudorascu ◽  
Spiridon Oprea ◽  
Afrodita Doina Marculescu ◽  
Stefania Tudorascu
Keyword(s):  
Hydrogen Peroxide ◽  
Tartaric Acid ◽  
Disperse System ◽  
Hydrogen Peroxide Solution ◽  
Ultrasonic Pretreatment ◽  
Tartaric Acids ◽  
Inactive Form ◽  
Generating System ◽  
Sole Product

The mechanism of the enzymatic iodination process of diethylmaleate and diethylfumarate (which present no miscibility with water) in the presence of lactoperoxidase, both in diluted hydrogen peroxide solution and in a generating system of hydrogen peroxide using ammonium and calcium iodides as halide sources in disperse system (after an ultrasonic pretreatment) was studied. The obtained sole product (diethyl-2, 3-diiodosuccinate) after the enzymatic iodination process was directly hydrolyzed to a tartaric acid present in an optically inactive form. The mechanism of obtaining the intermediate and final products and respectively, the existence of both D, L-tartaric acid and meso-tartaric acids (as lithium bitartrates) were also investigated.

A Short Enantioselective Synthesis of (S)-Levetiracetam Through Direct Pd-Catalyzed Asymmetric N-Allylation of Methyl 4-Aminobutyrate

Synlett ◽  
2021 ◽  
Author(s):  
Dominik Albat ◽  
Jörg-Martin Neudörfl ◽  
Hans-Günther Schmalz
Keyword(s):  
Antiepileptic Drug ◽  
Tartaric Acid ◽  
Enantioselective Synthesis

An exceedingly short and enantioselective synthesis of the antiepileptic drug (S)-levetiracetam was elaborated. As the chirogenic key step a Pd-catalyzed asymmetric N-allylation of methyl 4-aminobutyrate was achieved in the presence of only 1 mol% of a catalyst prepared in situ from [Pd(allyl)Cl]2 and the tartaric acid-derived C2-symmetric diphosphane ligand (S,S)-iPr-MediPhos).

The Differential Risk Factors of Physically Forced and Alcohol- or Other Drug-Enabled Sexual Assault Among University Women

2009 ◽  
Vol 24 (3) ◽  
pp. 302-321 ◽  
Author(s):  
Christopher P. Krebs ◽  
Christine H. Lindquist ◽  
Tara D. Warner ◽  
Bonnie S. Fisher ◽  
Sandra L. Martin
Keyword(s):  
High Risk ◽  
Sexual Assault ◽  
Future Research ◽  
Web Based ◽  
Campus Sexual Assault ◽  
University Women ◽  
Undergraduate Women ◽  
Reported Data ◽  
Lifestyle Activities ◽  
Very High

The Campus Sexual Assault Study examined whether undergraduate women’s victimization experiences prior to college and lifestyle activities during college were differentially associated with the type of sexual assault they experienced: physically forced sexual assault and incapacitated sexual assault. Self-reported data collected using a Web-based survey administered to more than 5,000 undergraduate women at two large public universities indicated that victimization experiences before college were differentially associated with the risk of experiencing these two types of sexual assault during college. Women who experienced forced sexual assault before college were at very high risk of experiencing forced sexual assault during college (odds ratio [OR] = 6.6). Women who experienced incapacitated sexual assault before college were also at very high risk of experiencing incapacitated sexual assault during college (OR = 3.7). Moreover, women’s substance use behaviors during college, including getting drunk and using marijuana, were strongly associated with experiencing incapacitated sexual assault but were not associated with experiencing forced sexual assault. Implications for education and prevention programs, as well as future research directions, are discussed.

scholarly journals Interrelationship of linear dimensions as growth corollary of pama croaker Otolithoides pama in the Bay of Bengal

2021 ◽  
Vol 32 (2) ◽  
pp. 287-292
Author(s):  
ZOARDER FARUQUE AHMED ◽  
MST. KANIZ FATEMA ◽  
UMME HABIBA AZ ZOHORA ◽  
MANSURA AKTER JOBA ◽  
FERDOUS AHAMED
Keyword(s):  
Bay Of Bengal ◽  
Correlation Coefficients ◽  
Future Research ◽  
Strongly Correlated ◽  
Regression Analyses ◽  
Allometric Growth ◽  
Linear Dimensions ◽  
Length Relationship ◽  
Gender Categories ◽  
Very High

Growth pattern of pama croaker Otolithoides pama population in the Bay of Bengal was determinedas the corollary of relationships between standard length (SL) and total length (TL), the two most prevalentlyused linear dimensions of fin fish species. Monthly pama croaker samples were collected from the industrialfisheries in the Bay of Bengal. The length-length relationship was constructed algebraically in the form ofy=a+bx. Relationships between SL and TL for male, female and unsexed populations were separatelyestablished. Sex ratio between male and female did not deviate from the parity (?2 test; p>0.05). The SL andTL ranges of male were 7.2-22 cm and 9.5-28 cm respectively, and the SL and TL ranges of female were6.8-20 cm and 8.4-25.7 cm respectively. Intercept and slope varied monthly in all length-length relationshipsregardless of gender categories. The generalized SL-TL relationships of male, female and unsexedpopulations were TL=1.214SL+0.761(R=0.989), TL=1.212SL-0.770(R=0.990) and TL=1.203SL+0.904(R=0.987) respectively. The correlation coefficients of both monthly and generalized regression analyses ofall sex types were very high (R?0.852) which explained that the relationships between the two lengthdimensions were strongly correlated. The growth corollary appeared both as isometric and allometric formonthly populations. Allometric growth was apparent in July, August and September in all gender types,while isometric growth was deduced in other months. This study would be useful for future research in orderto make comparisons with the relevant aspects of O. pama population between years and locations in the Bayof Bengal.

scholarly journals Composition, stability and stereo effects of zirconium(IV) dl-tartrate formation

2019 ◽  
Vol 57 (2) ◽  
pp. 28-34
Author(s):  
Lilia I. Mukhamedyarova ◽  
◽  
Sergey G. Bezryadin ◽  
Elena Yu. Klukvina ◽  
Vladimir V. Chevela ◽  
...  
Keyword(s):  
Tartaric Acid ◽  
Ph Value ◽  
Acid System ◽  
Alkaline Ph ◽  
Titration Method ◽  
Software Complex ◽  
Tartaric Acids ◽  
Potentiometric Titration Method ◽  
High Concentrations ◽  
Metal Ligand

The system of zirconium (IV) – dl-tartaric acid for metal: ligand 1: 1, 1: 2 and 1: 3 ratios in aqueous solution has been studied by means of using potentiometric titration method in combination with mathematical modeling. The comparison of Bjerrum functions from pH for zirconium(IV) systems: d-tartaric acid and zirconium (IV): dl-tartaric acid, has revealed the following features in the behavior of the curves: the degree of titration for the complexes at a fixed pH value for systems with dl-tartaric acid is more than for d-acid. The CPESSP software complex has calculated the composition, stability constants and molar fractions of zirconium(IV) tartrate accumulation. It has been also found that at a ratio of 1: 1 for Zr (IV) and ligand (H4Tart) ions in the system under study ZrHTart+ is formed, which is tetramerized into Zr4Tart40 and, further, tetranuclear particles of varying degrees of deprotonization are formed, as well as mononuclear forms. In a strongly alkaline pH environment > 10, Bjerrum curves for d- and dl-tartaric acids overlap each other and correspond to hydroxocomplexes of varying degrees of titration. For the 1: 2 ratio, the composition of the complexes for the zirconium(IV) – dl-H4T system is slightly different; compared to the zirconium(IV) – dH4T system, differences are clearly observed for both low and high concentrations. Based on these data, a complex formation scheme in the Zr(IV) – dl-tartaric acid system has been proposed for all the ratios studied. The characteristics of stereoselective diastereomer formation have been calculated. It has been revealed that in the medium of racemic tartrate, ddd- and lll-Zr(H2Tart)2(HTart)3-forms, as well as Zr(H2Tart)(НTart)24-Zr(HTart)35- are formed on a stereoselective basis.

Biology, Management, and Protection of North American Sturgeon

2002 ◽  
Keyword(s):  
Extinction Risk ◽  
High Rate ◽  
Future Research ◽  
Shortnose Sturgeon ◽  
Management Options ◽  
Connecticut River ◽  
Acipenser Brevirostrum ◽  
Survival And Reproduction ◽  
Very High ◽  
Existing Data

<em>Abstract.</em>—The shortnose sturgeon, <em>Acipenser brevirostrum</em>, is a long-lived species that grows slowly, matures at an advanced age, and spawns only intermittently. In the Connecticut River, there are two distinct subpopulations of shortnose sturgeon, which have been separated by the Holyoke Dam for 157 years. My research addressed the viability and persistence for these two separate populations and the effects of dispersal, variation in survival and reproduction, and catastrophes. My risk-based approach used a stage-based metapopulation model that I constructed in RAMAS<sup>®</sup> GIS incorporating the available data. Based on the existing data, this population model for the shortnose sturgeon metapopulation in the Connecticut River made several predictions. The observed stability of the two subpopulations was possible either: with reproduction in both upper and lower subpopulations and small to moderate rates of dispersal between them; or with no reproduction in the lower subpopulation, very high reproduction in the upper subpopulation and high rate of net downstream dispersal. My results provided estimates of extinction risk for the shortnose sturgeon metapopulation under various management options and highlighted three key areas for future research, demonstrating the value of a risk-based approach. This approach is particularly useful for management of long-lived aquatic species.

scholarly journals On the Robustness of Face Recognition Algorithms Against Attacks and Bias

2020 ◽  
Vol 34 (09) ◽  
pp. 13583-13589
Author(s):  
Richa Singh ◽  
Akshay Agarwal ◽  
Maneet Singh ◽  
Shruti Nagpal ◽  
Mayank Vatsa
Keyword(s):  
Face Recognition ◽  
Recognition Performance ◽  
Recognition Algorithm ◽  
Future Research ◽  
Research Directions ◽  
Recognition Algorithms ◽  
Future Research Directions ◽  
And Gender ◽  
Gender Variations ◽  
Very High

Face recognition algorithms have demonstrated very high recognition performance, suggesting suitability for real world applications. Despite the enhanced accuracies, robustness of these algorithms against attacks and bias has been challenged. This paper summarizes different ways in which the robustness of a face recognition algorithm is challenged, which can severely affect its intended working. Different types of attacks such as physical presentation attacks, disguise/makeup, digital adversarial attacks, and morphing/tampering using GANs have been discussed. We also present a discussion on the effect of bias on face recognition models and showcase that factors such as age and gender variations affect the performance of modern algorithms. The paper also presents the potential reasons for these challenges and some of the future research directions for increasing the robustness of face recognition models.

Sign in / Sign up

Export Citation Format

Share Document