Synthesis of a new 2‐amino‐glycan,poly‐(1→6)‐α‐D‐mannosamine,by ring‐opening polymerization of 1,6‐anhydro‐mannosamine derivatives

A stereoregular 2‐amino‐glycan composed of a mannosamine residue was prepared by ring‐opening polymerization of anhydro sugars. Two different monomers, 1,6‐anhydro‐2‐azido‐mannose derivative ( 3 ) and 1,6‐anhydro‐2‐(N, N‐dibenzylamino)‐mannose derivative ( 6 ), were synthesized and polymerized. Although 3 gave merely oligomers, 6 was promptly polymerized into high polymers of the number‐average molecular weight (M_n) of 2.3 × 10⁴ to 2.9 × 10⁴ with 1,6‐α stereoregularity. The differences of polymerizability of 3 and 6 from those of the corresponding glucose homologs were discussed. It was found that an N‐benzyl group is exceedingly suitable for protecting an amino group in the polymerization of anhydro sugars of a mannosamine type. The simultaneous removal of O‐ and N‐benzyl groups of the resulting polymers was achieved by using sodium in liquid ammonia to produce the first 2‐amino‐glycan, poly‐(1→6)‐α‐D ‐mannosamine, having high molecular weight through ring‐opening polymerization of anhydro sugars.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Flow microreactor synthesis of tricyclic sulfonamides via N-tosylaziridinyllithiums

Tricyclic sulfonamides were synthesized by the generation of aziridinyllithiums from N-tosylaziridines followed by an intramolecular nucleophilic reaction and the subsequent reaction with electrophiles using a flow microreactor system. The reactions could be carried out at 0 °C, although much lower temperatures such as ?78 °C are needed for batch macro reactors.     

Interference phenomenon on the complex degree of coherence

Optical Review - A two-beam interferometer (TBI) with a two-mode fiber (TMF) as a dispersive medium in one arm and air in the other provides evidence of interference related to the complex degree...     

Rigid diol bearing 6‐6‐6 fused ring system derived from naturally occurring myo‐inositol and its polyaddition with diisocyanates

Naturally occurring myo‐inositol was developed into a highly rigid diol by converting its 3,4‐ and 1,6‐vicinal diols in trans configuration into the corresponding butane‐2,3‐diacetals. The resulting diol bearing 6‐6‐6 fused ring system, in which conformational change is strictly suppressed, was combined with diisocyanates to perform polyadditions. The resulting polyurethanes were analyzed by differential scanning calorimetry, and it was found that their glass transition temperatures were much higher than those of the previously reported myo‐inositol‐derived polyurethanes, which were synthesized from a myo‐inositol‐derived diol bearing 5‐6‐5 fused ring system. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3798–3803     

Crystallization of Anodic Alumina Membranes Studied by Simultaneous TG-DTA/FTIR

The thermal change of anodic alumina (AA), particularly the exothermic peak followed by the endothermic peak at ca 950°C was studied in detail by mainly using simultaneous TG-DTA/FTIR. The gradual loss of mass up to ca 910°C is attributed to dehydration. When heated at a constant rate by using TG-DTA, an exothermic peak with subsequent endothermic peak is observed at ca 950°C, but the exothermic peak becomes less distinct with decreasing heating rate. It has been found that gaseous SO₂ accompanying a small amount of CO₂ is mainly discharged at this stage. The reaction in this stage can be considered roughly in two schemes. The first scheme can be said collectively as crystallization, in which the migration of S or C trapped inside the crystal lattice of the polycrystalline phase (γ-, δ-, and θ-Al₂O₃, which presumably accompanies a large amount of amorphous or disordered phase) occurs. In the second scheme, the initial polycrystalline (+amorphous) phase crystallizes into a quasi-crystallineγ-Al₂O₃-like metastable phase after amorphization. Conclusively,after the distinct exo- and endothermic reactions, the amorphous phase crystallizes intoγ-Al₂O₃, presumably accompanying small amount of δ-Al₂O₃. It is also found that, when maintained isothermally, the metastable phases undergo transformation into the stable α-Al₂O₃ at 912°C. This revised version was published online in July 2006 with corrections to the Cover Date.