R. Arnecke et al., REGIOSELECTIVE AND DIASTEREOSELECTIVE CONDENSATION OF RESORCARENES WITH PRIMARY AMINES AND FORMALDEHYDE, Tetrahedron letters, 36(35), 1995, pp. 6221-6224
Mannich reactions of resorcarenes 1 with chiral amines yield single di
astereomeric tetrakis-(benzodihydro-1,3-oxazine) derivatives 2 in high
yields (80-90%). Epimerisation of these products occurs in the presen
ce of acid.