An asymmetric ortholithiation approach to inherently chiral calix[4]arenes.
A general asymmetric synthesis of inherently chiral calix[4]arenes is described: using a chiral oxazoline derived from L-valine, an ortholithiation strategy is employed to give inherently chiral calix[4]arenes with high (93%) enantiomeric excesses. A crystal structure of a phosphine oxide intermediate has been obtained, unambiguously assigning the major diastereomer in the reaction; a mechanism explaining this result is proposed.
Herbert
Simon A
SA
Department of Chemistry and Polymer Science, University of Stellenbosch, Matieland 7602, South Africa.
Arnott
Gareth E
GE