Short and practical synthesis of O-(p-biphenoyl)-N-tosyl-allo-threonine-derived oxazaborolidinone catalyst.
O-(p-Biphenoyl)-N-tosyl-(L)-allo-threonine methyl ester is synthesized in three steps (65% overall yield) starting from commercially available (L)-allo-threonine methyl ester hydrochloride by N-acylation followed by N,O-acyl migration with inversion of the beta carbinol carbon and N-tosylation. Treatment of the methyl ester with dibromophenylborane gives oxazaborolidinone 1, which can be used as a Lewis acid catalyst for the asymmetric Michael and Diels-Alder reactions.
Harada
Toshiro
T
Department of Chemistry and Materials Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan. harada@chem.kit.ac.jp
Inui
Chieko
C