Copper(II)-catalyzed [2,3]-sigmatropic rearrangement of N-methyltetrahydropyridinium ylids

A ring-contractive and highly diastereoselective [2,3]-sigmatropic rearrangement occurs when N-methyl-1,2,3,6-tetrahydropyridine is treated with sub-stoichiometric amounts of copper or rhodium salts, in the presence of ethyl diazoacetate, giving ethyl cis-N-methyl-3-ethenyl proline (4).     

Fabrication of Super-Sized Metal Inorganic-Organic Hybrid Glass with Supramolecular Network via Crystallization-Suppressing Approach

Metal coordination compound (MCC) glasses [e.g., metal-organic framework (MOF) glass, coordination polymer glass, and metal inorganic-organic complex (MIOC) glass] are emerging members of the hybrid glass family. So far, a limited number of crystalline MCCs can be converted into glasses by melt-quenching. Here, we report a universal wet-chemistry method, by which the super-sized supramolecular MIOC glasses can be synthesized from non-meltable MOFs. Alcohol and acid were used as agents to inhibit crystallization. The MIOC glasses demonstrate unique features including high transparency, shaping capability, and anisotropic network. Directional photoluminescence with a large polarization ratio (≈47 %) was observed from samples doped with organic dyes. This crystallization-suppressing approach enables fabrication of super-sized MCC glasses, which cannot be achieved by conventional vitrification methods, and thus allows for exploring new MCC glasses possessing photonic functionalities.     

Ultracold atoms in optical lattices with random on-site interactions

We consider the physics of lattice bosons affected by disordered on-site interparticle interactions. Characteristic qualitative changes in the zero-temperature phase diagram are observed when compared to the case of randomness in the chemical potential. The Mott-insulating regions shrink and eventually vanish for any finite disorder strength beyond a sufficiently large filling factor. Furthermore, at low values of the chemical potential both the superfluid and Mott insulator are stable towards formation of a Bose glass leading to a possibly nontrivial tricritical point. We discuss feasible experimental realizations of our scenario in the context of ultracold atoms on optical lattices.     

Sulfated 1, 6-AnhydrO-4-O-(β-D-Glucopyranosyluronate)-β-D-Glucopyranosyl Derivatives: Syntheses And Conformations

Abstract

A series of sulfated 1,6-anhydro-4-O-(β-D-glucopyranosyluronate)-β-D-glucopyranose derivatives 7 and 9-13 with different degrees of charge was synthesized from a common disaccharide precursor 1,6-anhydro-2-azido-2-deoxy-4-O-(methyl2,3-di-O-benzyl-β-D-glucopyransyl-uronate-β-D-glucopyranose (5). For the 1,6-anhydro-β-D-glucopyranose moiety of this compound a boat-chair equilibrium is found, the boat conformation being stabilized by an intramolecular hydrogen bridge. The fully sulfated β-D-glucopyranosyl-uronates 10 and 13 occur in unusual nonchair conformations.     

Synthesis of 3-Fluoro-Oxetane δ-Amino Acids

Starting from d-xylose, 2,4-anhydro-5-N-(tert-butoxycarbonyl)amino-5-deoxy-3-fluoro-d-arabinonic acid 11 was synthesized over 10 steps including ring contraction, fluorination, and ester hydrolysis. Bromine oxidation of d-xylose followed by benzylidenation in a one-pot procedure led to a ca. 1:1 mixture of lactone 3 and 2,4;3,5-dibenzylidene xylonic acid (4) as by-product. For the synthesis of the d-xylo derivative 24, the chosen starting material was 1,2-O-isopropylidene-α-d-xylofuranose. A total of 14 steps including epimerization, ring contraction, fluorination, and saponification led to the desired fluoro-oxetane δ-amino acid 24. Hydrolysis of the 3-fluoro-oxetane δ-amino esters 10 and 23 by means of LiOH was successful in agreement with the results previously reported for similar 3-methoxy oxetanes, whereas chemical hydrolysis was not possible for 3-hydroxy derivatives.