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Total Synthesis of (+)‐Alexine by Utilizing a Highly Stereoselective [3+2] Annulation Reaction of an N ‐Tosyl‐α‐Amino Aldehyde and a 1,3‐Bis(silyl)propene
Author(s) -
Dressel Martina,
Restorp Per,
Somfai Peter
Publication year - 2008
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.200701776
Subject(s) - annulation , tosyl , pyrrolidine , stereoselectivity , aldehyde , chemistry , silylation , silyl ether , stereochemistry , pyrrolizidine , organic chemistry , catalysis
A novel route towards the polyhydroxylated pyrrolizidine alkaloid (+)‐alexine has been developed. A key step in this synthesis is a highly stereoselective [3+2] annulation reaction of N ‐Ts‐α‐amino aldehyde 7 a (Ts=tosyl) and 1,3‐bis(silyl)propene 8 a for the construction of the polyhydroxylated pyrrolidine subunit of the target molecule. Previous synthetic strategies rely on carbohydrates that require several protecting‐group manipulations, thereby making the total number of steps relatively high. The [3+2] annulation strategy compares favorably with carbohydrate‐based syntheses and constitutes a highly efficient entry to polyhydroxylated alkaloids.