The crystal structures of four dimethoxybenzaldehyde isomers

The crystal structures of four dimethoxybenzaldehyde (C9H10O3) isomers, namely the 2,3-, 2,4-, 2,5- and 3,5- isomers, are reported and compared to the previously reported crystal structures of 3,4-dimethoxybenzaldehyde and 2,6-dimethoxybenzaldehyde. All dimethoxybenzaldehyde molecules in the crystal structures are nearly planar. The largest deviation (1.2 Å) from the aromatic plane is found for one of the methoxy groups of 2,3-dimethoxybenzaldehyde. Upon rapid cooling of 3,4-dimethoxybenzaldehyde and 3,5-dimethoxybenzaldehyde, a metastable polymorph is formed. The crystal studied for the 3,5- isomer was refined as a two-component twin

Magnesium prevents vascular calcification in vitro by inhibition of hydroxyapatite crystal formation

Abstract Magnesium has been shown to effectively prevent vascular calcification associated with chronic kidney disease. Magnesium has been hypothesized to prevent the upregulation of osteoblastic genes that potentially drives calcification. However, extracellular effects of magnesium on hydroxyapatite formation are largely neglected. This study investigated the effects of magnesium on intracellular changes associated with transdifferentiation and extracellular crystal formation. Bovine vascular smooth muscle cells were calcified using β-glycerophosphate. Transcriptional analysis, alkaline phosphatase activity and detection of apoptosis were used to identify transdifferentiation. Using X-ray diffraction and energy dispersive spectroscopy extracellular crystal composition was investigated. Magnesium prevented calcification in vascular smooth muscle cells. β-glycerophosphate increased expression of osteopontin but no other genes related to calcification. Alkaline phosphatase activity was stable and apoptosis was only detected after calcification independent of magnesium. Blocking of the magnesium channel TRPM7 using 2-APB did not abrogate the protective effects of magnesium. Magnesium prevented the formation of hydroxyapatite, which formed extensively during β-glycerophosphate treatment. Magnesium reduced calcium and phosphate fractions of 68% and 41% extracellular crystals, respectively, without affecting the fraction of magnesium. This study demonstrates that magnesium inhibits hydroxyapatite formation in the extracellular space, thereby preventing calcification of vascular smooth muscle cells

The Crystalline Sponge Method in Water

The crystalline sponge method entails the elucidation of the (absolute) structure of molecules from a solution phase using single-crystal X-ray diffraction and eliminates the need for crystals of the target compound. An important limitation for the application of the crystalline sponge method is the instability of the available crystalline sponges that can act as host crystals. The host crystal that is most often used decomposes in protic or nucleophilic solvents or when guest molecules with Lewis basic substituents are introduced. Here we disclose a new class of (water) stable host crystals based on f-block metals. We show that these hosts not only increase the scope of the crystalline sponge method to a wider array of solvents and guests, but that they can even be applied to aqueous solutions containing hydrophilic guest molecules, thereby extending the crystalline sponge method to the important field of water-based chemistry

Photoracemization‐Based Viedma Ripening of a BINOL Derivative

BINOL=1,1’‐Bi‐2‐naphthol. Abstract Viedma ripening is a deracemization process that has been used to deracemize a range of chiral molecules. The method has two major requirements: the compound needs to crystallize as a conglomerate and it needs to be racemizable under the crystallization conditions. Although conglomerate formation can be induced in different ways, the number of racemization methods is still rather limited. To extend the scope of Viedma ripening, in the present research we applied UV‐light‐induced racemization in a Viedma ripening process, and report the successful deracemization of a BINOL derivative crystallizing as a conglomerate. Irradiation by UV light activates the target compound in combination with an organic base, required to promote the excited‐state proton transfer (ESPT), leading thereafter to racemization. This offers a new tool towards the development of Viedma ripening processes, by using a cheap and “green” catalytic source like UV light to racemize suitable chiral compounds

Enantiodivergent epoxidation of alkenes with a photoswitchable phosphate manganese-salen complex

The development of enantiodivergent catalysts capable of preparing both enantiomeric products from one substrate in a controlled fashion is challenging. Introducing a switching function into the catalyst can address this challenge, allowing the chiral reaction environment to reversibly change during catalysis. Here we report a photoswitchable phosphate ligand, derived from 2,2'-biphenol, which axially coordinates as the counter ion to an achiral manganese(III) salen catalyst, providing the latter with the ability to switch stereoselectivity in the epoxidation of alkenes. The enantiomers of the chiral ligand exist as a pair of pseudo-enantiomers, which can be interconverted by irradiation with light of different wavelengths. The opposite axial chirality of these pseudo-enantiomers is efficiently transferred to the manganese(III) salen catalyst. With this switchable supramolecular catalyst, the enantioselectivity of the epoxidation of a variety of alkenes can be controlled, resulting in opposite enantiomeric excesses of the epoxide products. This transfer of chirality from a photoswitchable anionic ligand to a metal complex broadens the scope of supramolecular catalysts