Highly asymmetric Pummerer-type cyclization of chiral, non-racemic β-amido sulfoxides
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The first highly asymmetric Pummerer-type cyclization of chiral, non-racemic β-amido sulfoxides to enantiomerically enriched β-lactams (80-85% ee) is described. S- and R-Sulfoxides (S-2a-d and R-2a-c) were treated with O-methyl-O-tert-butyldimethylsilyl ketene acetal 1 in the presence of a catalytic amount of zinc chloride in methylene dichloride to give predominantly the corresponding 4R- and 4S-β-lactams (R-3a-d and S-3a-c) in more than 80% ee. These results show that the stereoinduction is governed by the absolute configuration of the sulfoxides. Optically pure R- and S-3c were readily obtained by simple recrystallization in about 60% yield. The usefulness of the chiral, non-racemic 4-tolylsulfanyl-β-lactams 3a-d has been shown by their conversion into the key intermediate 11 for the optically pure carbapenem antibiotic, (+)-PS-5.
- Royal Society of Chemistryの論文
- 1995-01-01
Royal Society of Chemistry | 論文
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