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Bioinspired Divergent Oxidative Cyclization from Strictosidine and Vincoside Derivatives: Second‐Generation Total Synthesis of (−)‐Cymoside and Access to an Original Hexacyclic‐Fused Furo[3,2‐ b ]indoline
Author(s) -
Dou Yingchao,
Kouklovsky Cyrille,
Vincent Guillaume
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003758
Subject(s) - chemistry , indoline , tryptamine , stereochemistry , intramolecular force , aldol condensation , stereocenter , oxaziridine , organic chemistry , enantioselective synthesis , catalysis , biochemistry
The second‐generation synthesis of (−)‐cymoside as well as the formation of a new hexacyclic‐fused furo[3,2‐ b ]indoline framework is reported. After a Pictet–Spengler condensation between secologanin tetraacetate and tryptamine, the course of the cyclization of the 7‐hydroxyindolenine intermediate, generated by oxidation with an oxaziridine, depended on the stereochemistry of the 3‐position. The 3 ‐ ( S )‐strictosidine stereochemistry delivered efficiently the scaffold of cymoside via intramolecular coupling with the C16–C17 enol ether, while the 3 ‐ ( R )‐vincoside stereochemistry directed towards the reaction with the C18–C19 terminal alkene and the formation of the unexpected caged compound.