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RESEARCH PRODUCT

Novel lithocholaphanes: Syntheses, NMR, MS, and molecular modeling studies

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Abstract Novel head-to-head lithocholaphanes 6 and 11 have been synthesized via precursors 1 – 5 and 7 – 10 with overall good yields, and characterized by 1 H, 13 C, and 15 N NMR spectroscopy, ESI-TOF mass spectrometry, thermal analysis, and molecular modeling. In addition, the binding abilities of 6 and 11 towards alkali metal cations have been investigated via competitive complexation studies using equimolar mixtures of Li + , Na + , K + , and Rb + -cations, and cholaphanes 6 and 11 . The formation of cation–cholaphane adducts was detected by ESI-TOF mass spectrometry. The trends in these comparative binding studies are nicely reproduced theoretically with PM3 energetically optimized structures of 6 and 11 and their interaction energies with alkali metal cations calculated by molecular mechanics. Cholaphane 11 possessing a peptoid type structural fragment, –(CH 2 CONHCH 2 CH 2 ) 2 O–, as a coordination sphere, shows binding tendency towards lithium and sodium cations, whereas 6 possessing an ester type, –(CH 2 OCOCH 2 ) 2 O–, moiety and a bigger cavity size than 11 , shows merely a tendency towards bigger alkali metal cations, potassium and rubidium.