Conformational Analysis of Hydroxymethyl Group of D-Mannose Derivatives Using (6S)- and (6R)-(6-2H1)-D-Mannose

ABSTRACT

D-Mannose derivatives stereospecifically deuterated at C-6 were synthesized and the unequivocal ¹H NMR assignments of H-6proS and H-6pro R were made. The preferred conformation of the hydroxymethyl groups of these compounds are discussed.     

1H NMR Analyses of Rotameric Distribution of C5-C6 bonds of D-Glucopyranoses in Solution

Abstract

¹H NMR signals of H-6proR and H-6proS protons of D-glucoses and their per-O-acylated (acetyl and benzoyl) derivatives were unambiguously assigned by chiral deuteration at the C-6 position. The J_H5,H-6proR and J_H5,H-6proR values thus obtained enabled us to calculate the rotameric distributions of gg, gt and tg conformers. For the calculations, conventional equations (A and B) and novel equations accounting for possible departure of the three conformers from perfect staggering, were employed. The results showed that D-glucoses irrespective of solvents and protecting groups were predominant in two conformers gg and gt in an approximate ratio of 60 and 40, respectively, with a negligibly low population of the tg conformer. These results were in complete accordance with the statistical study of X-ray data of D-glucoses.     

Chiral Deuteration at C-6 of 1,6-Anhydrohexose Derivatives

Photobromination and the succeeding deuteration with tri-n-butyltindeuteride were performed on eight l,6-anhydro-2,3,4-tri-O-benzoylhexopyranoses to give C-6 chirally deuterated hexopyranoses. The stereochemistry of these two reactions are discussed in terms of steric effects of substituents at C-2, C-3 and C-4 of 1,6-anhydrohexopyranoses.     

Unexpected Formation of A 4,6-O-Propylidene Derivative from Galactose and Allyl Alcohol in the Presence of AmberlystR15

Abstract

Allyl ethers are convenient and widely used protecting groups in synthetic carbohydrate chemistry.² One of the attractive reactions of the allyl ether group is its ready isomerization into a prop-1-enyl ether function under basic or metal-mediated conditions.^2-4 In our research projects to extend galactosyltransferase reactions to the enzymic syntheses of βGal 1,1-linked sugars,⁵ 1-O-allyl galactopyranoside was needed as a key synthetic intermediate. Anhydrous cation exchange resin (Amberlyst^R15:Rohm & Haas Co.) was chosen as the acidic catalyst owing to its ease of handling and removal. In this paper we report an unexpected result of this reaction which gave allyl 4,6-O-propylidene galactopyranoside from galactose and Amberlyst in refluxing allyl alcohol.

On treatment of galactose (200 mg) and Amberlyst (100 mg) in allyl alcohol (5 mL) at 100–110 °C, TLC analysis (silica gel, acetonitrile:water, 10:1) indicated that the allyl glycosylation was completed within 15 min, affording allyl D-galactopyranoside.     

Highly enhanced enantioselectivity in the memory of chirality via acyliminium ions

[reaction: see text] Electrochemical oxidation of N-acylated serine derivative 1b in methanol gave optically active methoxylated compound 2b with an enantiomeric excess of up to 80%. The bulky o-phenyl benzoyl N-protecting group was found to be the main contributing factor for the enhanced enantioselectivity. The mechanistic aspect of this methoxylation reaction was investigated and found to proceed via a retention mechanism.     

Metabolites of Icariin in Urine Following Oral Administration

YinyanghuohasbeenusedinfolkmedicineforthousandsofyearsinChina.ItbelongstoplansofgenusEpimedinm(Berberidaceae).ChinaPharmcopoeia(l995Ed.)c0llectedfivespeciesofEpAnedium,inwhichflavanoidsareregardedastheprinciPalcomPonentsresponsibleforthePharmacologicalactivitiesofYinyanghuo,suchastonic,anti-hyPertensiveandami-inflarnmatoryactions.Icariinisoneofthemainflav0n0idconstituentsinYinyanghuo"'andextensivelyusedtocontrolthequalityofthecmdedrug."'TherearemanyrePortsonthepharmac0l0gical,chendcaland…     

Numerical simulation of soil–water interaction using smoothed particle hydrodynamics (SPH) method

An application of smoothed particle hydrodynamics (SPH) to simulation of soil–water interaction is presented. In this calculation, water is modeled as a viscous fluid with week compressibility and soil is modeled as an elastic–perfectly plastic material. The Mohr–Coulomb failure criterion is applied to describe the stress states of soil in the plastic flow regime. Dry soil is modeled by one-phase flow while saturated soil is modeled by separate water and soil phases. Interaction between soil and water is taken into account by means of pore water pressure and seepage force. Simulation tests of soil excavation by a water jet are calculated as a challenging example to verify the broad applicability of the SPH method. The excavations are carried out in two different soil models, one is dry soil and the other is fully saturated soil. Numerical results obtained in this paper have shown that the gross discontinuities of soil failure can be simulated without any difficulties. This supports the feasibility and attractiveness of this a new approach in geomechanics applications. Advantages of the method are robustness, conceptual simplicity and relative ease of incorporating new physics.     

α,α′‐Diarylacenaphtho[1,2‐c]phosphole P‐Oxides: Divergent Synthesis and Application to Cathode Buffer Layers in Organic Photovoltaics

A divergent method for the synthesis of α,α′‐diarylacenaphtho[1,2‐c]phosphole P‐oxides has been established; α,α′‐dibromoacenaphtho[c]phosphole P‐oxide, which was prepared through a Ti^II‐mediated cyclization of 1,8‐bis(trimethylsilylethynyl)naphthalene, underwent a Stille coupling with three different kinds of aryltributylstannanes to afford the α,α′‐diarylacenaphtho[c]phosphole P‐oxides in moderate to good yields. X‐ray crystallographic analyses and UV/Vis absorption/fluorescence measurements have revealed that the degree of π‐conjugation, the packing motif, the electron‐accepting ability, and the thermal stability of the acenaphtho[c]phosphole π‐systems are finely tunable with the α‐aryl substituents. All the P?O and P?S derivatives exhibited high stability in their electrochemically reduced state. To use this class of arene‐fused phosphole π‐systems as n‐type semiconducting materials, we evaluated device performances of the bulk heterojunction organic photovoltaics (OPV) that consist of poly(3‐hexylthiophene), an indene‐C₇₀ bisadduct, and a cathode buffer layer. The insertion of the diarylacenaphtho[c]phosphole P‐oxides as the buffer layer was found to improve the power conversion efficiency of the polymer‐based OPV devices.     

Reduced stress‐optical coefficient of polycarbonate by antiplasticization

We have investigated the effect of antiplasticization on the stress‐optical behavior of polycarbonate (PC) containing terphenyls (tPh) and di(2‐ethylhexyl)adipate (DEHA). Addition of the three tPhs (p‐, o‐, and m‐tPh) and DEHA at contents of 5–10 wt % increases the tensile storage modulus (E' ) of PC owing to the antiplasticization effect. In particular, p‐tPh increases E' more than the other additives, suggesting that the rod‐like shape matches the free volume of PC in the glassy state. The three tPh isomers improve the glassy birefringence of PC while DEHA does not change the glassy birefringence, which corresponds to the polarizability anisotropy. The stress‐optical coefficient, a ratio of stress and birefringence, of PC decreases with increasing additive content in order of p‐tPh ? o‐tPh > m‐tPh = DEHA. This result is agreement with a restricted rotational motion of additive molecule in PC, which is observed in dynamic mechanical and birefringence data. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1837–1842