Absolute Conformation and Chiroptical Properties. VI. 2,2′,3,3′-Tetramethoxy-9,9′-bitriptycyl: A Stereochemical Analog of 1,2-Disubstituted Ethane with Identical Substituents

The title compound was prepared by addition of 4,5-dimethoxybenzyne to 9,9′-bianthryl. The rotational isomers, ap and ±sc, were separated by HPLC. The ±sc isomers were treated with sodium ethanethiolate to produce 3,3′-dihydroxy-2,2′-dimethoxy-9,9′-bitriptycyl, which was converted to the ester of (1S,5R,7R)-4-[(2-carboxy)benzoyl]-3-thia-4-azatricyclo[5.2.1.01,5]decane 3,3-dioxide. The resulting diastereomers were separated by HPLC. The isomers were hydrolyzed and methylated with dimethyl sulfate to yield optically active 2,2′,3,3′-tetramethoxy-9,9′-bitriptycyl. The absolute conformation of the tetramethoxy compound was determined by X-ray structure analysis of 3′-ester of (1S,5R,7R)-4-(2-carboxybenzoyl)-3-thia-4-azatricyclo[5.2.1.01,5]decane 3,3-dioxide derived from 3-hydroxy-2,2′,3′-trimethoxy-9,9′-bitriptycyl, followed by hydrolysis and then methylation. The CD spectrum of Msc-2,2′,3,3′-tetramethoxy-9,9′-bitriptycyl is reported.