Determination of the Absolute Configuration of Inherently Chiral Resorc[4]arenes

Abstract The absolute configuration of twelve inherently chiral resorc‐arenes was determined using a combination of the X‐ray structure of (–)‐3a and optical rotation as well as NMR techniques. Starting from a racemic mixture of 1 both diastereomers (–)‐3a and (+)‐3b can be obtained in high yields in two steps and the absolute configuration of these diastereomers could be determined by X‐ray analysis. Using enantiomerically pure (–)‐1 for the same reactions, however, (+)‐3b is formed. The alkylation of (–)‐1 with (S)‐2‐methylbutyl tosylate and the methylation of (–)‐5a lead to the same resorcarene (–)‐4a, while the alkylation of (+)‐1 and the methylation of (+)‐5b yield in resorcarene (+)‐4b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)