First Synthesis, Isolation and Characterization of Enantiomerically Pure and Inherently Chiral Resorc[4]arenes by Lewis Acid Cyclization of a Resorcinol Monoalkyl Ether

摘要

Cyclization of resorcinol monoalkyl ethers with aliphatic aldehydes leads to the corresponding racemic mixtures of C_4-symmetric rccc-resorc[4]arenes, Separation of these isomers was achieved by mono-O-functionalization of the rccc-2,8,14,20-tetramethylresorc[4]arene (2) with (S)-(+)-10-cam-phorsulfonyl chloride leading to a diastereomeric mixture of (+)-5a and (-)-5b. After removal of the chiral auxiliary the inherently chiral pure enantiomers (+)-2 and (-)-2 were obtained. Further enantiomerically pure rccc-resorc[4]arenes were obtained by cyclization of (+)-3-[(2S)-2-methylbutoxyll-phenol (6) followed by chromatograhic separation. The resulting diastereomeric resorc[4]arenes (+)-7a and (-)-7b were examined by CD spectroscopy, showing a poerfect mir-ror image in all solvents examined. This indicates that the resorcarene cavities of (+)-7a and (-)-7b are essentially enantiomers of each other.