Described is a tetrabutylammonium fluoride-mediated hydroxyalkylation reaction of phenols with cyclic carbonates. This operationally simple method enables the synthesis of a variety of aryl β-hydroxyethyl ethers in good to excellent yields with a very small amount of catalyst loading (0.1-1 mol%). Of particular note is the efficient conversion of aromatic diols and phloroglucinol to the corresponding bis-and tris-hydroxyethylated products. To further showcase the versatility of this protocol, guaifenesin was prepared with a single step by the condensation of guaiacol and glycerol carbonate. We also developed a flow ethoxylation process permitting the continuous synthesis of multiflorol.
Described is a method for the transformation of a cyclic vinylogous ester to the corresponding polyarylated product. We found a catalytic system comprising palladium diacetate and tris(1-adamantyl)phosphine is quite effective in promoting a set of controlled cascade arylations. As a result, a range of novel (hetero)aryl-containing scaffolds was synthesized with a high level of efficiency.
Crinine and vittatine (the antipode of crinine) have long been, and remain, an inspiration for the development of reaction methods since their isolation in the 1950s. In particular, the all-carbon quaternary stereocenter embedded in these targets has fuelled creativity in innovating strategies and tactics of synthesis. This review provides an overview of research endeavors toward assembling the unique carboskeleton of the title alkaloids.
Using green, brown, and white cotton as materials, the contents of cellulose, carbohydrates, and flavonoid compounds as well as enzyme activities related to cellulose synthesis were investigated at various stages of fibre development to elucidate the characteristics of cellulose synthesis. The results showed that cellulose contents in all three cotton fibres showed 'S-shaped curve' changing patterns. According to a logistic growth model, the lower maximum accumulative rate of cellulose in the coloured cotton indicated less cellulose accumulation during fibre development. No significant differences in the carbohydrate content and carbohydrate transformation rates were observed between coloured and white cotton fibre. However, the flavonoid content in coloured cotton fibres was significantly higher than white cotton, and the flavonoid biosynthesis in coloured cotton fibres consumed a large amount of carbohydrates which should normally be used for cellulose synthesis. Low indoleacetic acid oxidase and peroxidase activities lowered cellulose accumulation in coloured cotton fibres. High activities of sucrose synthetase and β-1,3-glucanase in coloured cotton fibres may promote efficient utilization of carbohydrates. However, carbohydrate metabolism in the coloured cotton fibre should not only be responsible for cellulose biosynthesis but also for flavonoid biosynthesis.
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