Using a palladium(II)‐catalyzed oxidative cyclization as key‐step, we have developed short and efficient synthetic routes to clausenal (1) and its regioisomers 1,5‐dimethoxycarbazole‐3‐carbaldehyde (2) and 2,5‐dimethoxycarbazole‐3‐carbaldehyde (3). Our studies show that despite some discrepancies between the natural product and synthetic 1, the structural assignment for clausenal (1) most likely is
A new carbazole alkaloid designated as clausenal was isolated from the leaves of Clausena heptaphylla and its structure established as 1,8-dimethoxy-3-formylcarbazole from physical, chemical and synthetic evidence. The alkaloid was found to be active against both Gram-positive and Gram-negative bacteria, and fungi.
Synthesis of putative clausenal from carbazole using sequential C–H borylations
作者:Jessica Liyu、Jonathan Sperry
DOI:10.1016/j.tetlet.2017.03.051
日期:2017.4
A synthesis of the putative clausenal structure has been achieved from commercially available carbazole using a five-step sequence that features three iridium-catalyzed C-H borylation reactions. This conceptually disparate approach to carbazole synthesis further demonstrates the utility of the iridium-catalyzed borylation reaction in heteroaromatic C-H functionalization. The spectroscopic data of the synthetic sample casts doubt on the structure assigned to the natural product. (C) 2017 Elsevier Ltd. All rights reserved.