Highly diastereoselective functionalisation of calix[4]resorcinarene derivatives and acid catalysed epimerisation reactions

Mannich reactions of a number of calix[4]resorcinarene derivatives with (R)-(+)-α-methylbenzylamine under alkaline conditions lead to the formation of single diastereomeric tetrakis(1,3-dihydrobenzoxazine) derivatives in high yields; the reactions using the (S)-(-)-α-methylbenzylamine afford the enantiomers. The products react with protic acids to afford equilibrium mixtures of diastereomers.