Gelling Power Alteration on Kappa-Carrageenan Dispersion through Esterification Method with Different Fatty Acid Saturation

The physicochemical properties of κ-carrageenan gels and their ester forms derived from different fatty-acid saturations were characterized and compared with those of native κ-carrageenan. Furthermore, stearic and oleic acids were used as the saturated and unsaturated fatty acids, respectively. Fourier-transform infrared (FTIR) spectra confirmed the introduction of the ester into the κ-carrageenan backbone. The thermogravimetric analysis showed that thermal stability increased along with the level of unsaturation, but there was a decrease in viscosity, hardness, and syneresis, which caused the consistency of the product to become more elastic. The results also showed that the ester form still has a swelling ability that is almost the same as that of κ-carrageenan. After being formulated into a gel dosage form, the product was successfully produced from the ester with unsaturated fatty acids, and it was more elastic than native κ-carrageenan and had good physical properties with spreadability that meets the requirements for topical preparations.

Four-Selective Pyridine Alkylation via Wittig Olefination of Dearomatized Pyridylphosphonium Ylides

Methods to synthesize alkylated pyridines are valuable because these structures are prevalent in pharmaceuticals and agrochemicals. We have developed a distinct approach to construct 4-alkylpyridines using dearomatized pyridylphosphonium ylide intermediates in a Wittig olefination-rearomatization sequence. Pyridine N-activation is key to this strategy, and N-triazinylpyridinium salts enable coupling between a wide variety of substituted pyridines and aldehydes. The alkylation protocol is viable for late-stage functionalization, including methylation of pyridine-containing drugs. This approach represents an alternative to metal-catalyzed sp² -sp³ cross-coupling reactions and Minisci-type processes.

Development of a triazinedione-based dehydrative condensing reagent containing 4-(dimethylamino)pyridine as an acyl transfer catalyst

A new triazinedione-based reagent, (N,N'-dialkyl)triazinedione-4-(dimethylamino)pyridine (ATD-DMAP) was developed for the operationally simple dehydrative condensation of carboxylic acids. This reagent comprises an ATD core and DMAP as the leaving group, which is liberated into the reaction system to accelerate acyl transfer reactions. Upon adding ATD-DMAP to a mixture of carboxylic acids and alcohols in the presence of an amine base, the corresponding esters were formed rapidly at room temperature. Moreover, dehydrative condensation between carboxylic acids and amines using ATD-DMAP proceeded in high yield.

Selective Chemical Labeling and Sequencing of 5-Carboxylcytosine in DNA at Single-Base Resolution

5-Carboxylcytosine (5caC) plays a vital role in the dynamics of DNA demethylation, and sequencing of its sites will help us dig out more biological functions of 5caC. Herein, we present a novel chemical method to efficiently label 5caC distinguished from other bases in DNA. Combined with bisulfite sequencing, 5caC sites can be located at single-base resolution, and the efficiency of 5caC labeling is 92% based on the Sanger sequencing data. Furthermore, dot blot assays have confirmed that 5caC-containing DNA isolated from HeLa cells was successfully labeled using our method. We expect that our strategy can be further applied to selectively tagging other carboxyl-modified bases and mapping their sites in RNA.

Kinetic Analysis as an Optimization Tool for Catalytic Esterification with a Moisture-Tolerant Zirconium Complex

This work describes the use of kinetics as a tool for rational optimization of an esterification process with down to equimolar ratios of reagents using a recyclable commercially available zirconocene complex in catalytic amounts. In contrast to previously reported group IV metal-catalyzed esterification protocols, the work presented herein circumvents the use of water scavengers and perfluorooctane sulfonate (PFOS) ligands. Insights into the operating mechanism are presented.