Asymmetric Hydrogenation of α-Amino Esters into Optically Active ß-Amino Alcohols through Dynamic Kinetic Resolution Catalyzed by Ruthenabicyclic Complexes.

Racemic α-substituted α-amino esters were hydrogenated into enantioenriched ß-amino alcohols through dynamic kinetic resolution with chiral ruthenabicyclic complexes. The reaction was carried out with a substrate/catalyst molar ratio of 200-1000 under 15 atm of H2 at 25 °C to afford a variety of ß-substituted ß-aminoethanols in up to 96% ee (24 examples). The mechanistic studies including deuteration experiments suggested that the reaction proceeds with 1,2-hydride migration of the α-amino acetalate intermediate into the α-hydroxy imine followed by the continuous reduction of the imino compound, affording the amino alcohol product.

Association between Physical Frailty Subdomains and Oral Frailty in Community-Dwelling Older Adults.

This cross-sectional study aimed to demonstrate the association between physical frailty subdomains and oral frailty. This study involved community-dwelling older adults (aged ≥65 years). Physical frailty was assessed with the Japanese version of the Cardiovascular Health Study criteria. Oral frailty was defined as limitations in at least three of six domains. Logistic regression analysis was used to analyze the association between physical frailty risk and oral frailty. In addition, we examined the association between physical frailty subdomains (gait speed, grip strength, exhaustion, low physical activity, and weight loss) and oral frailty. A total of 380 participants were recruited for this study. Overall, 18% and 14% of the participants were at risk of physical frailty and had oral frailty, respectively. Physical frailty risk (odds ratio (OR) = 2.40, 95% confidence interval (CI): 1.22-4.75, p = 0.012) was associated with oral frailty in multivariate analysis. In secondary analysis, among physical frailty subdomains, gait speed (OR = 0.85, 95% CI: 0.73-0.97, p = 0.019) was associated with oral frailty. The present findings suggest that physical frailty is closely related to oral frailty. Among physical frailty subdomains, decreased gait speed in particular is an important indicator related to the development of oral frailty.

Double Asymmetric Hydrogenation of Linear ß,ß-Disubstituted α,ß-Unsaturated Ketones into γ-Substituted Secondary Alcohols using a Dual Catalytic System.

Double asymmetric hydrogenation of linear ß,ß-disubstituted α,ß-unsaturated ketones catalyzed by the DM-SEGPHOS/DMAPEN/RuII complex with t-C4 H9 OK afforded the γ-substituted secondary alcohols in high diastereo- and enantioselectivities. Some mechanistic experiments suggested that two different reactive species, type (I) and (II), were reversibly formed in this catalytic system: Type (I) with the diamine ligand DMAPEN enantioselectively hydrogenated the enones into the chiral allylic alcohols, and type (II) without the diamine ligand diastereoselectively hydrogenated the allylic alcohols into the γ-substituted secondary alcohols. This dual catalysis protocol was successfully applied to the reaction of a variety of aliphatic- and aromatic-substituted enone substrates.

Acoustical power amplification and damping by temperature gradients.

Ceperley proposed a concept of a traveling wave heat engine ["A pistonless Stirling engine-The traveling wave heat engine," J. Acoust. Soc. Am. 66, 1508-1513 (1979).] that provided a starting point of thermoacoustics today. This paper verifies experimentally his idea through observation of amplification and strong damping of a plane acoustic traveling wave as it passes through axial temperature gradients. The acoustic power gain is shown to obey a universal curve specified by a dimensionless parameter ωτα; ω is the angular frequency and τα is the relaxation time for the gas to thermally equilibrate with channel walls. As an application of his idea, a three-stage acoustic power amplifier is developed, which attains the gain up to 10 with a moderate temperature ratio of 2.3.