Highly Diastereoselective Chelation-Controlled 1,3-anti-Allylation of (S)-3-(Methoxymethyl)hexanal Enabled by Hydrate of Scandium Triflate

En route to the total synthesis of (+)-Neopeltolide, we explored Lewis acid-assisted diastereoselective allylation of MOM-protected 3-hydroxylhexanal with β-(2,2-diethoxyethyl)-substituted (allyl)tributylstannane. The hydrated form of scandium triflate was found to be essential for attaining high 1,3-anti-diastereoselectivity (d.r. 94:6), while the use of anhydrous catalyst resulted in a modest diastereocontrol (d.r. 76:24). The preferred 1,3-anti-selectivity in this transformation can be rationalized in the framework of the Reetz chelate model of asymmetric induction. The 1,3-anti-configuration of the product was confirmed by its conversion into the known C7-C16 building block of (+)-Neopeltolide. We also report an improved protocol for the synthesis of β-(2,2-diethoxyethyl)-substituted (allyl)tributylstannane, which can be utilized as a cost-efficient bipolar isoprenoid-type C5-building block in the synthesis of natural compounds.

Structural Systematics of Lanthanide(III) Picrate Solvates: Neutral, Mononuclear Ln(pic)3(dimethylsulfoxide)3 Arrays

Adducts of dimethylsulfoxide, dmso=Me2SO, with lanthanide(iii) picrates (picrate=2,4,6-trinitrophenoxide, pic) of stoichiometry Ln(pic)3·3dmso have been prepared and characterised by single-crystal X-ray structure determinations as discrete, neutral, mononuclear molecular species. Such complexes have been obtained across the gamut of Ln, specifically for Ln=La, Pr, Nd, Sm, Gd, Dy, Yb, Lu, and Y, presumably also accessible for other intermediate members, the series being isomorphous (monoclinic, C2/c, Z=8); a second triclinic P form has also been identified for Ln=La, Pr. In both forms, the metal atom coordination environments are nine-coordinate, tricapped trigonal prismatic, [Ln(dmso-O)3(pic-O,O′)3], two of the three unidentate ligands lying in one of the trigonal planes and one in the other (an isomer we have termed meridional, mer). A hydrated form of Ln(pic)3·2dmso·H2O stoichiometry has also been defined for Ln=Sm, Gd, Lu, the metal atom environment again nine-coordinate, [Ln(dmso-O)2(H2O)(pic-O,O′)3], but now fac, with the three unidentate ligands occupying one triangular face of the tricapped trigonal prism and involved in a centrosymmetric H-bonding array with the three similar ligands of an adjacent complex; the three capping atoms are nitro-oxygen atoms, the phenoxy-O triad occupying the other face.

A novel crystal form of metacetamol: the first example of a hydrated form

We report the crystal structure and crystallization conditions of a first hydrated form of metacetamol (a hemihydrate), C8H9NO2·0.5H2O. It crystallizes from metacetamol-saturated 1:1 (v/v) water–ethanol solutions in a monoclinic structure (space group P21/n) and contains eight metacetamol and four water molecules per unit cell. The conformations of the molecules are the same as in polymorph II of metacetamol, which ensures the formation of hydrogen-bonded dimers and R 2 2(16) ring motifs in its crystal structure similar to those in polymorph II. Unlike in form II, however, these dimers in the hemihydrate are connected through water molecules into infinite hydrogen-bonded molecular chains. Different chains are linked to each other by metacetamol–water and metacetamol–metacetamol hydrogen bonds, the latter type being also present in polymorph I. The overall noncovalent network of the hemihydrate is well developed and several types of hydrogen bonds are responsible for its formation.

Synthesis and Evaluation of Cyclic Sulfite Diesters as Sulfur Dioxide (SO2) Donors

<div>Although sulfur dioxide (SO₂) finds widespread use in the food industry as its hydrated form, sulfite, a number of aspects of SO₂biology remain to be completely understood. Among the tools available for intracellular enhancement of SO₂, most suffer from poor cell permeability and a lack of control over SO₂ release. We report 1,2-cyclic sulfite diesters as a new class of reliable SO₂donors that dissociate in buffer through a nucleophilic displacement to produce SO₂with tuneable release profiles. We provide data in support of the suitability of these SO₂donors to enhance intracellular levels of SO₂at an efficiency superior to sodium bisulfite, the most commonly used SO₂ donor for cellular studies.</div>

Synthesis and Evaluation of Cyclic Sulfite Diesters as Sulfur Dioxide (SO2) Donors

<div>Although sulfur dioxide (SO₂) finds widespread use in the food industry as its hydrated form, sulfite, a number of aspects of SO₂biology remain to be completely understood. Among the tools available for intracellular enhancement of SO₂, most suffer from poor cell permeability and a lack of control over SO₂ release. We report 1,2-cyclic sulfite diesters as a new class of reliable SO₂donors that dissociate in buffer through a nucleophilic displacement to produce SO₂with tuneable release profiles. We provide data in support of the suitability of these SO₂donors to enhance intracellular levels of SO₂at an efficiency superior to sodium bisulfite, the most commonly used SO₂ donor for cellular studies.</div>

Technological Solutions for the Realization of NGH-Technology for Gas Transportation and Storage in Gas Hydrate Form

The technology of transportation and storage of gas in a gas-hydrated form under atmospheric pressure and slight cooling – the maximum cooled gas-hydrated blocks of a large size covered with a layer of ice are offered. Large blocks form from pre-cooled mixture of crushed and the granulated mass of gas hydrate. The technology of forced preservation gas hydrates with ice layer under atmospheric pressure has developed to increase it stability. The dependence in dimensionless magnitudes, which describes the correlation-regressive relationship between the temperature of the surface and the center gas hydrate block under its forced preservation, had proposed to facilitate the use of research results. Technology preservation of gas hydrate blocks with the ice layer under atmospheric pressure (at the expense of the gas hydrates energy) has designed to improve their stability. Gas hydrated blocks, thus formed, can are stored and transported during a long time in converted vehicles without further cooling. The high stability of gas hydrate blocks allows to distributed in time (and geographically) the most energy expenditure operations – production and dissociation of gas hydrate. The proposed technical and technological solutions significantly reduce the level of energy and capital costs and, as a result, increase the competitiveness of the stages NGH technology (production, transportation, storage, regasification).