Total synthesis of (+)-brasilenyne. Application of an intramolecular silicon-assisted cross-coupling reaction |
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Authors: | Denmark Scott E Yang Shyh-Ming |
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Institution: | Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA. denmark@scs.uiuc.edu |
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Abstract: | The first enantioselective total synthesis of (+)-brasilenyne (1) has been achieved in 19 linear steps, with 5.1% overall yield from l-(S)-malic acid. The construction of the oxonin core containing a 1,3-cis,cis diene unit was accomplished with a tandem ring-closing metathesis/silicon-assisted intramolecular cross-coupling reaction. In addition, a key propargylic stereogenic center was created through a novel, highly diastereoselective ring opening of a 1,3-dioxolanone promoted by TiCl(4). This reaction proceeded through an oxocarbenium ion intermediate and the asymmetric induction was fully controlled by l-malic acid residue. The C(8) stereogenic center was set by a reagent-controlled asymmetric allylboration. |
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