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Synthesis of 12‐ epi ‐Protopanaxadiol and Formal Synthesis of Ginsenoside Chikusetsusaponin‐LT 8
Author(s) -
Evanno Laurent,
Belotti Damien,
Toromanoff Edmond,
Cossy Janine
Publication year - 2019
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201901031
Subject(s) - chemistry , stereochemistry , allylic rearrangement , ring (chemistry) , epoxide , context (archaeology) , radical cyclization , ketone , combinatorial chemistry , catalysis , organic chemistry , paleontology , biology
In the context of the total synthesis of protopanaxadiol, two strategies were explored. One strategy from an optically active trienic epoxide, possessing a 5‐membered ring, prepared from ( S )‐epoxy‐limonene and ( S )‐epoxyfarnesol, which was submitted to Ti‐(III)‐mediated radical cascade to afford an original tetracyclic structure resulting from a 6‐ endo ‐ trig 6‐ endo ‐ trig 8‐ endo ‐ trig process. A second strategy, starting from a Wieland‐Miescher‐type ketone, using a “ring‐by‐ring” synthesis allowed the synthesis of 12‐ epi ‐protopanaxadiol. In this latter strategy, an efficient sequence of reactions to install the two vicinal C8–C14 quaternary centers involves: i) a Barbier type reaction; ii) an oxidative allylic transposition and iii) a nickel‐catalyzed addition of trimethylaluminium. By using this second strategy, 20‐hydroxydammar‐24‐ene‐3,12‐dione was synthesized which represents a formal synthesis of chikusetsusaponin‐LT 8 , isolated from Panax japonicus .