Lower rim through the annulus

The means by which the cone conformer (u,u,u,u) of a calix[4]arene is transformed to its inverted cone conformer (d,d,d,d) remains somewhat uncertain, although it clearly involves a lower rim through the annulus pathway (see Section 4.5.1), One possibility is that the process is concerted (a continuous chain pathway ) without intermediates and only one transition state. Another possibility is that the process is stepwise (a broken chain pathway ) with intermediates and two or more transition states, e.g. cone partial cone - 1,2- or... 

Two pathways are available to a calixarene for conformational inversion. One involves the upper rim through the annulus and the other involves the lower... 

Calix[4]arenes with unprotected OH groups in the lower rim undergo through-annulus inversion and therefore cannot be inherently chiral. The substitution of OH groups with alkyl chains (of at least n-Pr size) blocks the inversion and the resulting... 

---