Reactions of coordinated hydroxymethylphosphines with NH-functional amines: the phosphorus lone pair is crucial for the phosphorus Mannich reaction

Non-coordinated hydroxymethylphosphines react readily with primary and secondary amines by the phosphorus Mannich reaction. To determine if this reactivity can be used to synthesize phosphine macrocycles, trans-Fe(DHMPE)(2)Cl(2) (DHMPE = 1,2-bis(dihydroxymethylphosphino)ethane) was prepared and reacted with various amines. However, no phosphorus Mannich reactivity was observed. In order to understand why no reactions occurred, the Mannich reactivity of the borane-coordinated hydroxymethylphosphines DHMPE·2BH(3) and Ph(2)PCH(2)OH·BH(3) was investigated. These borane-coordinated phosphines also did not undergo the phosphorus Mannich reaction. These results suggest that the lone pair of electrons on the phosphorus atom is essential for the phosphorus Mannich reaction to occur, and therefore it is not possible to use this reaction in a templated synthesis of phosphine macrocycles. It is speculated that the mechanism of the phosphorus Mannich reaction may involve a methylenephosphonium intermediate, analogous to an iminium in the standard Mannich reaction. X-ray crystal structures of trans-Fe(DHMPE)(2)Cl(2) and DHMPE·2BH(3) are also presented. Both crystal structures display an extended hydrogen-bonding network in the solid state.     

Stereoselective total synthesis of aminoiminohexitols via carbamate annulation

New methodology for the preparation of a variety of aminoiminohextitols is described. Key in the synthesis is the application of a diastereoselective Strecker reaction and the extension of our carbamate annulation methodology to protected and functionalized alkenylamines. Insight into the effects that the substitution patterns of the alkenylamines have on the diastereoselectivity of the iodocyclization and carbamate annulation is discussed. An evaluation of the glycosidase inhibitory activity of the aminoiminohexitols and derivatives is also presented, with the previously undisclosed D-talo isomer showing good selective inhibition of β-D-glucosidase.     

Potential Benefits of Black Chokeberry (Aronia melanocarpa) Fruits and Their Constituents in Improving Human Health

Aronia berry (black chokeberry) is a shrub native to North America, of which the fresh fruits are used in the food industry to produce different types of dietary products. The fruits of Aronia melanocarpa (Aronia berries) have been found to show multiple bioactivities potentially beneficial to human health, including antidiabetic, anti-infective, antineoplastic, antiobesity, and antioxidant activities, as well as heart-, liver-, and neuroprotective effects. Thus far, phenolic compounds, such as anthocyanins, cyanidins, phenolic acids, proanthocyanidins, triterpenoids, and their analogues have been identified as the major active components of Aronia berries. These natural products possess potent antioxidant activity, which contributes to the majority of the other bioactivities observed for Aronia berries. The chemical components and the potential pharmaceutical or health-promoting effects of Aronia berries have been summarized previously. The present review article focuses on the molecular targets of extracts of Aronia berries and the examples of promising lead compounds isolated from these berries, including cyanidin-3-O-galactoside, chlorogenic acid, quercetin, and ursolic acid. In addition, presented herein are clinical trial investigations for Aronia berries and their major components, including cancer clinical trials for chlorogenic acid and COVID-19 trial studies for quercetin. Additionally, the possible development of Aronia berries and their secondary metabolites as potential therapeutic agents is discussed. It is hoped that this contribution will help stimulate future investigations on Aronia berries for the continual improvement of human health.     

Purposeful Control

At present both management and biological sciences are faced with a common problem in methodology—how to model systems of organized complexity. In their approach to this problem the management sciences have adopted several concepts from the biological sciences, such as adaptation, goal-seeking, purposefulness, and so on, but have as yet donated little in return.This paper offers a contribution towards redressing the balance. A simple mathematical model of purposeful control is presented, and quantitative examples are then given to illustrate the application of the model to both living and practical systems.     

Enclathration of morpholinium cations by Dianin's compound: salt formation by partial host-to-guest proton transfer

In spite of partial deprotonation upon inclusion of morpholine, Dianin's compound maintains its well-known clathrate structure in the solid state.     

Frequency resolution and discrimination of constant and dynamic tones in normal and hearing-impaired listeners

Frequency resolution and three tasks of frequency discrimination were measured at 500 and 4000 Hz in 12 normal and 12 hearing-impaired listeners. A three-interval, two-alternative forced-choice procedure was used. Frequency resolution was measured with an abbreviated psychoacoustical tuning curve. Frequency discrimination was measured for (1) a fixed-frequency standard and target, (2) a fixed-frequency standard and a frequency-transition target, and (3) frequency-transition standard and a frequency-transition target. The 50-ms frequency transitions had the same final frequency as the standards, but the initial frequency was lowered to obtain about 79% discrimination performance. There was a strong relationship between poor frequency resolution and elevated pure-tone thresholds, but only a very weak relationship between poor frequency discrimination and elevated pure-tone thresholds. Several hearing-impaired listeners had normal discrimination performance together with pure-tone thresholds of 80-90 dB HL. A slight correlation was found between word recognition and frequency discrimination, but a detailed comparison of the phonetic errors and either the frequency-discrimination or frequency-resolution tasks failed to suggest any consistent interdependencies. These results are consistent with previous work that has suggested that frequency resolution and frequency discrimination are independent processes.     

Isogenies of elliptic curves and the Morava stabilizer group

Let S₂ be the p-primary second Morava stabilizer group, C a supersingular elliptic curve over , O the ring of endomorphisms of C, and ? a topological generator of (or if p=2). We show that for p>2 the group Γ⊆O[1/?]^× of quasi-endomorphisms of degree a power of ? is dense in S₂. For p=2, we show that Γ is dense in an index 2 subgroup of S₂.     

Spectral asymptotics for Kac–Murdock–Szegő matrices

Szeg?’s First Limit Theorem provides the limiting statistical distribution of the eigenvalues of large Toeplitz matrices. Szeg?’s Second (or Strong) Limit Theorem for Toeplitz matrices gives a second order correction to the First Limit Theorem, and allows one to calculate asymptotics for the determinants of large Toeplitz matrices. In this paper we survey results extending the First and Second Limit Theorems to Kac–Murdock–Szeg? (KMS) matrices. These are matrices whose entries along the diagonals are not necessarily constants, but modeled by functions. We clarify and extend some existing results, and explain some apparently contradictory results in the literature.