First C3v-symmetrical calix[6](aza)crown.

The first C(3v)-symmetrical calix[6](aza)crown 8 has been obtained in five steps from X(6)H(3)Me(3) 3. The key-step introduction of the triple bridge at the small rim has been achieved through reaction of a tris-arylsulfonamide derivative of tren 1 and tris-tosylcalix[6]arene 6. A (1)H NMR study has shown that the tripodal cap rigidifies the whole edifice, preventing ring inversion and constraining the calixarene core in a straight cone conformation.