Highly stereoselective oxy-Michael additions to alpha,beta-disubstituted nitro olefins: asymmetric synthesis of pseudo-norephedrine derivatives and THP* protected alpha-hydroxy ketones |
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Authors: | Buchanan David J Dixon Darren J Hernandez-Juan Felix A |
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Institution: | Department of Chemistry, University of Cambridge, UK. |
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Abstract: | The "naked" anion of (S)-6-methyl delta lactol undergoes efficient oxy-Michael addition to alpha,beta-disubstituted nitro olefins to give the THP* protected Henry products with excellent (95-->98% de) stereocontrol at the beta-position and moderate (up to 3 : 1) stereocontrol at the alpha-position in favour of the syn-diastereoisomer. Nitro group reduction with in situN-Boc protection and THP* removal provides alpha,beta-disubstituted ethanolamine derivatives, while treatment with tetrapropylammonium perruthenate gives THP* protected alpha-hydroxy ketone derivatives in high diasteromeric excess. |
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