Total Syntheses of Trichorabdal A and Maoecrystal Z

Abstract

This work reports the total syntheses of Isodon diterpenes trichorabdal A and maoecrystal Z via a common bicyclo[3.2.1]octane intermediate, which chemically bridges the two distinct structures through a retro-aldol/aldol reaction cascade. Other synthetic features include an efficient cross-ring radical cyclization for rapid construction of an all carbon quaternary center commonly seen in Isodon diterpenoids, a challenging Ueno-Stork cyclization on to a sensitive 1,6-enone system, as well as a serial of chemoselective functional group manipulations in complex chemical environments.

Total Synthesis of (−)‐Arborisidine

“…In the retrosynthetic analysis (Scheme 1 a), we hypothesized that radical addition might be a suitable method to forge the C14‐C15 linkage, which avoids the formation of a carbanion neighboring the C−N bond. According to this design, arborisidine is derived from intermediate 5 , which is the expected 5‐ exo‐trig radical cyclization product of allylic thioether 6 [11] . We anticipated that, an intramolecular dearomative allylic alkylation of substrate 8 , followed by a regioselective functionalization of the exocyclic alkene in intermediate 7 could afford intermediate 6 .…”

“…According to this design, arborisidine is derived from intermediate 5, which is the expected 5-exo-trig radical cyclization product of allylic thioether 6. [11] We anticipated that, an intramolecular dearomative allylic alkylation of substrate 8, followed by a regioselective functionalization of the exocyclic alkene in intermediate 7 could afford intermediate 6. The Barbier-type addition of bromide 10 [12] to harmalane (9) [13] is an ideal choice for the preparation of 8.…”

Pd‐Catalyzed Regio‐ and Diastereoselective Heck Cyclization to Access Bicyclo[3.2.1]octanone Ring Systems

“…These molecules share a tetracyclic framework, which feature a spiro‐lactone fused‐bridged ring junction. Sculponeatin N ( 1 ) and trichorabdal A ( 2 ) among others had caught attention from synthetic community and surged several elegant total syntheses from Reisman, Zhai, Thomas and Liang . We were intrigued by the poly‐fused bridged skeleton as well as their biological activities, thus embarking on their total synthesis.…”

Design, synthesis and antimycobacterial activity of novel nitrobenzamide derivatives

“…In our previous studies, many BTZs containing various cyclic ketoximes, spiro-heterocycles and piperidines moieties were found to have considerable antitubercular activity [27][28][29]. Recently, N-(4-(4trifluoromethyl)piperidin-1-yl)benzyl nitrobenzamides 1 and 2 ( Fig.…”