Toward the development of a general chiral auxiliary. A total synthesis of (+)-tetronolide via a tandem ketene-trapping [4+2] cycloaddition strategy

摘要

A highly convergent, enantioselective total synthesis of the aglycone of the tetrocarcins, (+)-tetronolide, is described. The synthesis highlights the use of several new methods, including camphor auxiliary-directed asymmetric alkylation and the enantioselective preparation of acyclic mixed acetals bearing chirality at the acetal center, and the highly efficient connection of the two major precursors via a ketene-trapping/ intramolecular [ 4 + 2] cycloaddition strategy.