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Exploiting the Pd- and Ru-catalyzed cycloisomerizations: enantioselective total synthesis of (+)-allocyathin B2.

ABSTRACT: Pd- and Ru-catalyzed cycloisomerizations of 1,6-enynes are compared and contrasted. Such considerations led to the enantioselective synthesis of a cyathin terpenoid, (+)-allocyathin B(2) (1). The synthesis features a Pd-catalyzed asymmetric allylic alkylation (AAA) to install the initial quaternary center, a Ru-catalyzed diastereoselective cycloisomerization to construct the six-membered ring, and a diastereoselective hydroxylative Knoevenagel reaction to introduce the final hydroxyl group. We demonstrate for the first time a mechanism-based stereochemical divergence in Pd- and Ru-catalyzed cycloisomerization reactions as well as in creation of alkene geometry with alkynes bearing a carboalkoxy group. Mechanistic rationalization is proposed for these observations.

SUBMITTER: Trost BM

PROVIDER: S-EPMC2565572 | biostudies-literature | 2005 Jul

REPOSITORIES: biostudies-literature

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Exploiting the Pd- and Ru-catalyzed cycloisomerizations: enantioselective total synthesis of (+)-allocyathin B2.

Trost Barry M BM Dong Li L Schroeder Gretchen M GM

Journal of the American Chemical Society 20050701 29

Pd- and Ru-catalyzed cycloisomerizations of 1,6-enynes are compared and contrasted. Such considerations led to the enantioselective synthesis of a cyathin terpenoid, (+)-allocyathin B(2) (1). The synthesis features a Pd-catalyzed asymmetric allylic alkylation (AAA) to install the initial quaternary center, a Ru-catalyzed diastereoselective cycloisomerization to construct the six-membered ring, and a diastereoselective hydroxylative Knoevenagel reaction to introduce the final hydroxyl group. We d ...[more]

PMID: 16028937

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