[reaction: see text] The first enantioselective total synthesis of convolutamydines B and E has been achieved using our vinylogous Mukaiyama aldol reaction. The synthesis features highly diastereoselective vinylogous Mukaiyama aldol reaction with isatin instead of aldehydes to construct a chiral center of convolutamydines. Additionally, the absolute configuration of natural convolutamydine B has been determined as R by its CD spectrum.
The vinylogous Mukaiyama aldol reaction (VMAR) of chiral nonracemic ketene silyl N,O-acetal with various aldehydes is demonstrated. VMAR with alpha-heteroatom-unsubstituted aldehydes proceeded with a high degree of anti-selectivity. In sharp contrast, moderate to high syn-selectivity was observed when alpha-heteroatom-substituted aldehydes were used.
[structure: see text] A convergent total synthesis of khafrefungin was accomplished on the basis of (1) the highly stereoselective TiCl4-mediated vinylogous Mukaiyama aldol reaction using vinylketene silyl N,O-acetal and (2) syn-selective aldol reaction of enal 5a and ethyl ketone 6 followed by anti-dehydration under Mitsunobu conditions.
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