An efficient synthesis of the C1−C17 western unit of narasin was achieved from (S)-Roche ester. Highlights in our synthesis include the successful exploitation of three stereoselective sequences of Lewis acid mediated reaction followed by free-radical-based hydrogen transfer.
Synthesis of Propionate Motifs: Diastereoselective Tandem Reactions Involving Anionic and Free Radical Based Processes
作者:Yvan Guindon、Karine Houde、Michel Prévost、Benoit Cardinal-David、Serge R. Landry、Benoit Daoust、Mohammed Bencheqroun、Brigitte Guérin
DOI:10.1021/ja010805m
日期:2001.9.1
employing a Mukaiyama reaction in tandem with a hydrogen transfer reaction for the elaboration of propionate motifs. The nature of the protecting groups on the chiral β-alkoxy aldehyde and the type of Lewis acid used are varied to modulate the stereochemical outcome of the tandemreactions. The mode of complexation is thus controlled (monodentate or chelate) for the Mukaiyama reaction to give access to
Diastereoselective Radical Hydrogen Transfer Reactions using N-Heterocyclic Carbene Boranes
作者:Guillaume Tambutet、Yvan Guindon
DOI:10.1021/acs.joc.6b02066
日期:2016.11.18
Reported herein are the first diastereoselective and Lewis acid-mediated radical reactions of N-heterocyclic carbene (NHC) boranes. We applied these reactions to the synthesis of four propionate diastereoisomers combining an aldol reaction, followed by a stereoselective radical-based reduction in which the NHC borane serves as the hydrogen donor, thus obviating the use of tin-based reagents. The 2