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We have developed a method for synthesizing novel helical amide derivatives. Nucleophilic primary amines were inserted into benzo-fused 2,2′-biphenoquinones to form helical amides containing seven-membered rings. When optically pure primary amines were used in this reaction, a mixture of two amide diastereoisomers was obtained and separated into diastereomerically pure products by high-performance liquid chromatography. In contrast, the reaction of enantiomerically pure benzo-fused 2,2′-biphenoquinones with achiral aliphatic primary amines afforded enantiomerically pure helical amides with stereospecificity and retention of configuration. [ABSTRACT FROM AUTHOR]

Enantiomerically pure 9-substituted 11-oxa[9]helicene derivatives have been synthesized through furan-ring formation by a nucleophilic cyclodehydration reaction of enantiomerically pure helical polycondensed 2,2′-diphenoquinone derivatives (1,1′-bibenzo[ c ]phenanthrenylidene-2,2′-diones). (P)-2,2′-diphenoquinone derivatives afforded (P)-oxa[9]helicenes, whereas (M)-2,2′-diphenoquinone derivatives afforded the corresponding (M)-oxa[9]helicenes. Therefore, the ring-closing reaction afforded the corresponding enantiomerically pure products without decreasing the enantiomeric excess, and it proceeded stereospecifically with retention of the configuration. The thermal stability of an oxa[9]helicene was studied by determining the decrease in its enantiomeric excess at various temperatures, and its racemization barrier was found to be 165.6 kJ/mol. [ABSTRACT FROM AUTHOR]