Synthesis of erythrina and related alkaloids. XXII. Intramolecular cyclization approach. (1): New synthetic route to erythrinan and related heterocycles and synthesis of (±)-3-demethoxyerythratidinone
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Tsuda,Sakai,Nakai,Kaneko,Ishiguro,Isobe,Taga,Sano
p. 1462 - 1472
(2007/10/02)
A PRACTICAL ROUTE TO SPIRO-TYPE HETEROCYCLES RELATED TO ERYTHRINAN
A new method synthesizing spiro-type heterocycles by intramolecular cyclization of 3,3-disubstituted dioxopyrrolines was presented.The method is particularly useful in synthesizing erythrinans and has the following advantages: 1) it is of short steps with high yield ( one-pot reaction is possible ), 2) an activating group at ring A is not necessary, and 3) the procedure can be carried out without protection of phenolic hydroxyl groups.Wide applicability of this method was also shown by synthesizing C-nor and C-homoerythrinans, and other variants which carry heterocycles at ring A instead of benzenoids.