An asymmetric total synthesis of ent‐ancistrocladinium A was developed via chiral phosphoric acid‐catalyzed asymmetric reductive amination of 1‐aryl‐2‐propanone and naphthylamine followed by a Bischler–Napieralski reaction. Direct use of the naphthyl moiety in the amine as a key building block in the natural product allowed us to achieve the total synthesis of ancistrocladinium A in only three steps from the known starting materials.
A general strategy for the total asymmetric synthesis of valuable tropane alkaloids by catalytic stereoselective transformations is disclosed. The power of this approach is exemplified by the concise catalytic enantioselective total syntheses of (+)‐methylecgonine, (−)‐cocaine and (+)‐cocaine as well as the first catalytic asymmetric total syntheses of a cocaine C‐1 derivative and (+)‐ferruginine starting from 5‐oxo‐protected‐α,β‐unsaturated enals using only two and three column chromatographic purification steps, respectively. 相似文献
Kopsinine and related alkaloids are attractive synthetic targets because of their structural complexity and biological activities. An organocatalytic Michael addition/aza‐Michael addition/cyclization cascade sequence has been developed for the enantioselective preparation of tetracyclic spiroindolines from 2,3‐disubstituted indoles and propargyl aldehyde in moderate to good yields and good to excellent enantioselectivities. The synthetic value of these advanced structures has been demonstrated by the synthesis of kopsinine and related alkaloids. Key steps for the concise synthesis of these alkaloids included an efficient enantioselective construction of tetracyclic spiroindolines bearing a dienamino ester moiety and the organocatalyzed nucleophilic addition of a dienamino ester to acrolein.
HR4, a member of the nuclear receptor family, has been extensively studied in insect molting and development, but reports on crustaceans are still lacking. In the current study, the MnHR4 gene was identified in Macrobrachium nipponense. To further improve the molting molecular mechanism of M. nipponense, this study investigated whether MnHR4 functions during the molting process of M. nipponense. The domain, phylogenetic relationship and 3D structure of MnHR4 were analyzed by bioinformatics. Quantitative real-time PCR (qRT-PCR) analysis showed that MnHR4 was highly expressed in the ovary. In different embryo stages, the highest mRNA expression was observed in the cleavage stage (CS). At different individual stages, the mRNA expression of MnHR4 reached its peak on the fifteenth day after hatching (L15). The in vivo injection of 20-hydroxyecdysone (20E) can effectively promote the expression of the MnHR4 gene, and the silencing of the MnHR4 gene increased the content of 20E in M. nipponense. The regulatory role of MnHR4 in 20E synthesis and 20E signaling was further investigated by RNAi. Finally, the function of the MnHR4 gene in the molting process of M. nipponense was studied by counting the molting frequency. After knocking down MnHR4, the molting frequency of M. nipponense decreased significantly. It was proved that MnHR4 plays a pivotal role in the molting process of M. nipponense. 相似文献
