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Total Synthesis of the Alkaloid (±)‐Aspidophytine Based on Carbonyl Ylide Cycloaddition Chemistry
Author(s) -
MejíaOneto José M.,
Padwa Albert
Publication year - 2008
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200890034
Subject(s) - chemistry , iminium , cycloaddition , total synthesis , ylide , imide , ring (chemistry) , cascade reaction , stereochemistry , alkaloid , lactone , domino , azomethine ylide , medicinal chemistry , cleavage (geology) , fragmentation (computing) , organic chemistry , 1,3 dipolar cycloaddition , ion , catalysis , operating system , geotechnical engineering , fracture (geology) , computer science , engineering
The Rh II ‐catalyzed cycloaddition cascade of an indolyl‐substituted α ‐diazo imide was used for the total synthesis of the complex pentacyclic alkaloid (±)‐aspidophytine. Treatment of the resulting dipolar cycloadduct with BF 3 ⋅OEt 2 induces a domino fragmentation cascade. The reaction proceeds by an initial cleavage of the oxabicyclic ring and formation of a transient N ‐acyl iminium ion which reacts further with the adjacent tert ‐butyl ester and sets the required lactone ring present in aspidophytine. A three‐step sequence was then used to remove both the ester and OH groups. Subsequent functional group manipulations allowed for the high‐yielding conversion to (±)‐aspidophytine.