Isolation and structural analysis of novel conformational isomers of the m-xylylene-bridged calix[6]arenes: the ‘partial cone’ and ‘inverted cone’ isomers

In the benzylation of a m-xylylene-bridged calix6]arene tetrol, the first example of the ‘partial cone’ isomer of a calix6]arene was obtained in addition to the corresponding cone and 1,2,3-alternate isomers, and its structure was established by X-ray crystallographic analysis. The synthesis and crystal structure of the ‘inverted cone’ isomer as well as its thermal conversion to the ‘normal cone’ isomer are also described.