Zirconocene-catalyzed epoxy ester - ortho ester rearrangement: A new method for the protection of polyfunctionalized carboxylic acids and the asymmetric synthesis of ortho esters

Article abstract of DOI:10.1016/S0040-4020(97)01038-7

In situ prepared Cp₂(CI)Zr⁺ catalyzes the formation of ortho esters from epoxy esters. Acid-sensitive α-amino and α-hydroxy acid derivatives are converted in high yield to 2,7,8- trioxabicyclo[3.2.1]octanes (ABO-esters) using this protocol. This strategy is complementary to the OBO-ester technology, and orthogonal methods for the deprotection of ABO- and OBO-esters have been developed. The syntheses of the mushroom components (S)-γ- hydroxyleucine lactone and (S)-α-vinylglycine underline the value of ABO-ester protective group strategy. Using chiral epoxy alcohol derivatives, the first convenient and general asymmetric synthesis of bicyclic ortho esters has been achieved.