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A Concise Synthesis of (−)‐Indolizidines 209D and 209B
Author(s) -
WU Hao,
YU Menglong,
ZHANG Yazhu,
ZHAO Gang
Publication year - 2009
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.200990015
Subject(s) - chemistry , indolizidine , aldehyde , ketone , stereoselectivity , bicyclic molecule , substrate (aquarium) , methyl ketone , stereochemistry , combinatorial chemistry , organic chemistry , alkaloid , catalysis , oceanography , geology
Abstract A general stereoselective synthetic route to 5‐substituted and 5,8‐disubstituted indolizidine alkaloids has been developed starting from commercially available L ‐proline. (−)‐Indolizidines 209D and 209B were efficiently synthesized in 9.8% and 14.8% overall yields in seven and five‐step reactions from readily available aldehyde 3 and ketone 10 , respectively. The key steps of this synthesis involve a substrate‐induced asymmetric addition of ethyl lithiopropiolate to aldehyde 3 or methyl ketone 10 , and a two‐step one‐pot hydrogenation/cyclization sequence to construct the bicyclic skeleton.