31 research outputs found
Book Recommendation Based on Library Loan Records and Bibliographic Information
AbstractIn order to show the effectiveness of using (a) library loan records and (b) information about book contents as a basis for book recommendations, we entered various data into a support vector machine (SVM), used it to recommend books to subjects, and asked them for evaluations of the recommendations that were given. The data that we used were (1) confidence and support with an association rule that was based on the loan records, (2) similarities between book titles, (3) matches/mismatches between the Nippon Decimal Classification (NDC) categories of the books, and (4) similarities between the outlines of the books in the BOOK Database. The subjects were 32 students who belonged to T University. The books that we recommended and the loan records that we used were obtained from the T University Library. The results showed that the combinations of (1), (2), (3) and (1), (2) were rated more favorably by the subjects than the other combinations. However, the books that were recommended by Amazon were rated even more favorably by the subjects. This is a topic for further research
Electrophilic iodine(I) compounds induced semipinacol rearrangement via C-X bond cleavage.
Neutral electrophilic iodine(I) species proved to be efficient reagents for C-X bond cleavage of various cyclic and acyclic α-silyloxyhalides, and the induced desilylative semipinacol rearrangement provided the corresponding ketones in good yields. The reaction is operationally simple, and proceeds under mild conditions with good functional group compatibility. Mechanistic investigations, including computational studies, were also performed
Catalytic asymmetric synthesis of the pentacyclic core of (-)-nakadomarin A via oxazolidine as an iminium cation equivalent.
A facile and catalytic asymmetric synthesis of the pentacyclic core of (-)-nakadomarin A, containing all the stereogenic centers of the natural product was achieved. The key intermediate involves the oxazolidine moiety as an iminium cation equivalent. An efficient method for the removal of the N-hydroxyethyl group is also described
Effects of Fatty Liver Induced by Excess Orotic Acid on B-Group Vitamin Concentrations of Liver, Blood, and Urine in Rats
Carbohydrate intake is associated with time spent in the euglycemic range in patients with type 1 diabetes.
[Aims/Introduction]Greater glycemic variability and lack of predictability are important issues for patients with type 1 diabetes. Dietary factors are one of the contributors to this variability, but how closely diet is linked to glycemic fluctuation on a daily basis has not been investigated. We examined the association between carbohydrate intake and glycemic excursion in outpatients. [Materials and Methods]A total of 33 patients with type 1 diabetes were included in the analyses (age 44.5 ± 14.7 years, diabetes duration 15.1 ± 8.3 years, 64% female, 30% using insulin pump, glycated hemoglobin 8.1 ± 1.3%). Time spent in euglycemia (70–180 mg/dL), hyperglycemia (>180 mg/dL) and hypoglycemia (<70 mg/dL) of consecutive 48-h periods of continuous glucose monitoring data were collected together with simultaneous records of dietary intake, insulin dose and physical activity. Correlation analyses and multiple regression analyses were used to evaluate the contribution of carbohydrate intake to time spent in the target glycemic range. [Results]In multiple regression analyses, carbohydrate intake (β = 0.53, P = 0.001), basal insulin dose per kg per day (β = −0.31, P = 0.034) and diabetes duration (β = 0.30, P = 0.042) were independent predictors of time spent in euglycemia. Carbohydrate intake (β = −0.51, P = 0.001) and insulin pump use (β = −0.34, P = 0.024) were independent predictors of time spent in hyperglycemia. Insulin pump use (β = 0.52, P < 0.001) and bolus insulin dose per kg per day (β = 0.46, P = 0.001) were independent predictors of time spent in hypoglycemia. [Conclusions]Carbohydrate intake is associated with time spent in euglycemia in patients with type 1 diabetes
Direct Dehydroxylative Coupling Reaction of Alcohols with Organosilanes through Si–X Bond Activation by Halogen Bonding
The combined use
of a halogen bond (XB) donor with trimethylsilyl halide was found
to be an efficient cocatalytic system for the direct dehydroxylative
coupling reaction of alcohol with various nucleophiles, such as allyltrimethylsilane
and trimethylcyanide, to give the corresponding adduct in moderate
to excellent yields. Detailed control experiments and mechanistic
studies revealed that the XB interaction was crucial for the reaction.
The application of this coupling reaction is also described
Confinement-Controlled, Either syn- or anti-Selective Catalytic Asymmetric Mukaiyama Aldolizations of Propionaldehyde Enolsilanes
Protected aldols (i.e., true aldols derived from aldehydes) with either syn- or anti- stereochemistry are versatile intermediates in many oligopropionate syntheses. Traditional stereoselective approaches to such aldols typically require several nonstrategic operations. Here we report two highly enantioselective and diastereoselective catalytic Mukaiyama aldol reactions of the TBS- or TES- enolsilanes of propionaldehyde with aromatic aldehydes. Our reactions directly deliver valuable silyl protected propionaldehyde aldols in a catalyst controlled manner, either as syn- or anti- isomer. We have identified a privileged IDPi catalyst motif that is tailored for controlling these aldolizations with exceptional selectivities. We demonstrate how a single atom modification in the inner core of the IDPi catalyst, replacing a CF3-group with a CF2H-group, leads to a dramatic switch in enantiofacial differentiation of the aldehyde. The origin of this remarkable effect was attributed to tightening of the catalytic cavity via unconventional C-H hydrogen bonding of the CF2H group
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Catalytic asymmetric cationic shifts of aliphatic hydrocarbons.
Asymmetric catalysis is an advanced area of chemical synthesis, but the handling of abundantly available, purely aliphatic hydrocarbons has proven to be challenging. Typically, heteroatoms or aromatic substructures are required in the substrates and reagents to facilitate an efficient interaction with the chiral catalyst. Confined acids have recently been introduced as tools for homogenous asymmetric catalysis, specifically to enable the processing of small unbiased substrates1. However, asymmetric reactions in which both substrate and product are purely aliphatic hydrocarbons have not previously been catalysed by such super strong and confined acids. We describe here an imidodiphosphorimidate-catalysed asymmetric Wagner-Meerwein shift of aliphatic alkenyl cycloalkanes to cycloalkenes with excellent regio- and enantioselectivity. Despite their long history and high relevance for chemical synthesis and biosynthesis, Wagner-Meerwein reactions utilizing purely aliphatic hydrocarbons, such as those originally reported by Wagner and Meerwein, had previously eluded asymmetric catalysis
Predicting Highly Enantioselective Catalysts Using Tunable Fragment Descriptors
Catalyst optimization process is typically relying on an inductive and qualitative assumption of chemists based on screening data. While machine learning models using molecular properties or calculated 3D structures enable quantitative data evaluation, costly quantum chemical calculations are often required. In contrast, readily available binary fingerprint descriptors are time- and cost-efficient, but their predictive performance remains insufficient. Here, we describe a machine learning model based on fragment descriptors, which are fine-tuned for asymmetric catalysis and represent cyclic or polyaromatic hydrocarbons, enabling robust and efficient virtual screening. Using training data with only moderate selectivities, we designed theoretically and validated experimentally new catalysts showing higher selectivities in a previously unaddressed transformation