In this study, lithocholic acid (LCA) was prepared using commercially available plant-sourced bisnoralcohol (BA), and the overall yield of the product was 70.6% for five steps. To prevent process-related impurities, the isomerizations of catalytic hydrogenation in the C4−C5 double bond and reduction of the 3keto group were optimized. The double bond reduction isomerization was improved (5β-H:5α-H = 97:3) using palladium− copper nanowires (Pd−Cu NWs) instead of Pd/C. The reduction of the 3-keto group was 100% converted to a 3α-OH product by 3α-hydroxysteroid dehydrogenase/carbonyl reductase catalysis. Moreover, the impurities during the optimization process were comprehensively studied. Compared with the reported synthesis methods, our developed method significantly improved the isomer ratio and overall yield, affording ICH-grade quality of LCA, and it is more cost-effective and suitable for large-scale production of LCA.
Various indole-containing compounds have shown impressive pharmaceutical activities against a variety of diseases. However, the functionalization of indoles usually relies on systems that use organic solvents, which do not meet the criteria for green and sustainable chemical development. To address this issue, regiospecific sulfenylation, selenylation, and telluration of indoles were developed using H2O as solvent. The highly efficient chalcogenylation of indoles was achieved utilizing CsOH as a promoter, thus avoiding the use of expensive transition-metal catalysts. This newly developed protocol is characterized by its outstanding features including simple operation, mild conditions, wide substrate scope, excellent functional group tolerance, and recyclability, leading to the convenient synthesis of 3-chalcogenyl-indoles.
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