Anionic inverse electron-demand 1,3-dipolar cycloaddition of nitrones with ynolates. Facile stereoselective synthesis of 5-isoxazolidinones leading to beta-amino acids

[reaction: see text] The inverse electron-demand 1,3-dipolar cycloaddition of nitrones with ynolates, followed by quenching with t-BuOH, produced substituted 5-isoxazolidinones with good trans-selectivity. These products were easily converted into beta-amino acids.     

Synthesis and chiral recognition of helical poly(phenylacetylene)s bearing l‐phenylglycinol and its phenylcarbamates as pendants

A series of novel stereoregular one‐handed helical poly(phenylacetylene) derivatives ( PPA‐1 and PPA‐1a～g ) bearing l ‐phenylglycinol and its phenylcarbamate residues as pendants was synthesized for use as chiral stationary phases (CSPs) for HPLC, and their chiral recognition abilities were evaluated using 13 racemates. The phenylcarbamate residues include an unsubstituted phenyl, three chloro‐substituted phenyls (3‐Cl, 4‐Cl, 3,5‐Cl₂), and three methyl‐substituted phenyls (3‐CH₃, 4‐CH₃, 3,5‐(CH₃)₂). The acidity of the phenylcarbamate N‐H proton and the hydrogen bonds formed between the N‐H groups of the phenylcarbamate residues were dependent on the type, position, and the number of substituents on the phenylcarbamate residues. The chiral recognition abilities of these polymers significantly depended on the dynamic helical conformation of the main chain with more or less regularly arranged pendants. The chiral recognition abilities seem to be improved by the introduction of substituents on the phenylcarbamate residues, and PPA‐1d bearing the more acidic N‐H groups due to the 3,5‐dichloro substituents, exhibited a higher chiral recognition than the others. PPA‐1d showed an efficient chiral recognition for some racemates, and baseline separation was possible for racemates 5 , 11 , 12 , and 15 . © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 809–821     

Concentrated Equilibrium and Intraday Patterns in Financial Markets

Abstract

We introduce endogenous participation of market makers into a Kyle-type model with long-lived asymmetric information. In our model with plausible parameter values, the trading volume and price volatility show a U-shaped intraday pattern, often observed in actual financial markets. It will be shown that the pattern is caused not only by the trading behaviour of liquidity traders but also by that of market makers. Our findings shed new light on the stylized fact of the trade concentration at the opening and closing periods.     

Entanglement properties of cellulose and amylose in an ionic liquid

Concentrated solutions of cellulose and amylose were prepared with an ionic liquid 1‐butyl‐3‐methylimidazolium chloride (BmimCl), which was chosen as a good solvent for these polysaccharides. Dynamic viscoelasticity of the concentrated solutions was examined to obtain the molecular weight between entanglements, M_e. The value of M_e in the molten state (M_e,melt), a material constant that reflecting the entanglement properties, was determined for cellulose and amylose by extrapolating M_e to the “melt.” A marked difference in M_e,melt was found: 3.2 × 10³ for cellulose and 2.5 × 10⁴ for amylose. The value of M_e,melt for cellulose, which is composed of β‐(1,4) bonding of D ‐glucose units, is very close to those for polysaccharides with a random‐coil conformation such as agarose and gellan in BmimCl. The much larger M_e,melt for amylose can be attributed to the helical nature of the amylose chain, α‐(1,4)‐linked D ‐glucose units. The effect of concentration on the zero‐shear viscosity for the solutions of cellulose and amylose was also examined. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Synthesis of (−)‐Morphine: Application of Sequential Claisen/Claisen Rearrangement of an Allylic Vicinal Diol

A detailed exploration of the synthesis of (?)‐morphine based on sequential [3,3]‐sigmatropic rearrangements is described. The sequential Claisen/Claisen rearrangements of an allylic vicinal diol resulted in the stereoselective formation of the two contiguous carbon centers, including a sterically encumbered quaternary carbon, in a single operation. The two ethyl esters generated in this reaction were successfully differentiated during a subsequent Friedel–Crafts‐type cyclization. The (?)‐morphine double bond was introduced at a late stage in our first‐generation synthesis, but was formed at an earlier stage in the second‐generation synthesis, resulting in a more efficient route to the end product.     

Antioxidant effects of photodegradation product of nifedipine

Recently, increasing evidence suggests that the antihypertensive drug nifedipine acts as a protective agent for endothelial cells, and that the activity is unrelated to its calcium channel blocking. Nifedipine is unstable under light and reportedly decomposes to a stable nitrosonifedipine (NO-NIF). NO-NIF has no antihypertensive effect, and it has been recognized as a contaminant of nifedipine. The present study for the first time demonstrated that NO-NIF changed to a NO-NIF radical in a time-dependent manner when it interacted with human umbilical vein endothelial cells (HUVECs). The electron paramagnetic resonance (EPR) signal of NO-NIF radicals in HUVECs showed an asymmetric pattern suggesting that the radicals were located in the membrane. The NO-NIF radicals had radical scavenging activity for 1,1-diphenyl-2-picrylhydrazyl, whereas neither NO-NIF nor nifedipine did. In addition, the NO-NIF radical more effectively quenched lipid peroxides than NO-NIF or nifedipine. Furthermore, NO-NIF attenuated the superoxide-derived free radicals in HUVECs stimulated with LY83583, and suppressed iron-nitrilotriacetic acid (Fe-NTA)-induced cytotoxicity in rat pheochromocytoma (PC12) cells. Our findings suggest that NO-NIF is a candidate for a new class of antioxidative drugs that protect cells against oxidative stress.