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

Abstract

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)