Macrolides, which comprise a family of lactones with different ring sizes, belong to the polyketide class of natural products. Resorcinolic macrolides, an important subgroup, possess interesting structures and exhibit a wide variety of bioactivities, such as anti-tumor, anti-bacteria, and anti-malaria activities, etc. This review summarizes progress in isolation, bioactivity studies, biosynthesis, and representative chemical syntheses of this group of macrolides in recent decades, encompassing 63 naturally occurring macrolides published in 120 articles.
As a kind of excellent diesel-blending component, polyoxymethylene dimethyl ethers (PODEn) have received widespread attention. Herein, Al-SBA-15 molecular sieves with different Si/Al ratios and pore sizes were synthesized and used to investigate the catalytic performance for the synthesis of polyoxymethylene dimethyl ethers from methylal and trioxane. X-ray diffraction, N 2 adsorption−desorption, scanning electron microscopy, transmission electron microscopy, X-ray fluorescence, and 27 Al NMR were used to characterize the structures of obtained catalysts. Ammonia temperature-programmed desorption and pyridine adsorption were carried out to investigate the acid properties of the catalysts. Through comparison of the catalysts with different Al contents, it was found that the relatively weak acid was more suitable for the synthesis of PODEn than the relatively strong acid in the catalytic system of Al-SBA-15. On the Al-SBA-15(2)-150 catalyst, which has only a weak acid of 0.163 mmol/g, the highest TOX conversion rate and highest PODEn yield and selectivity were achieved, showing the best catalytic performance. It appears that the PODEn synthesis can be catalyzed by not only a Bronsted acid but also a Lewis acid. The catalysts with strong acid and/or with a large number of acids will cause the generation of significant amount of methyl formate byproduct. Through comparison of the catalysts with different pore sizes, it was found that a relative larger pore size of the catalyst was beneficial for the PODEn synthesis to a certain extent under the catalysts with strong acid and/or large acid amount, but on the catalyst that had only weak acid and a relatively lesser amount, the change of pore size had almost no effect on the yield and selectivity of PODEn products.
Sulfonic acid-functionalized mesoporous SBA-15 with different sulfur loading was synthesized and used to investigate the catalytic performance for PODEn synthesis.
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