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Functional chimeras: New bingel-hirsch-type steroid-fullerene hybrids

Abstract:

Cyclopropanations between C60 and readily available malonates bearing different steroid moieties (4-6) by the Bingel-Hirsch protocol, has allowed, the synthesis of a new series of hybrid functionalized chimeras (7-9). Whereas cycloadducts 7 and 8 showed the expected chemical structures, the presence of the diene moiety in the ergosterol unit of malonate 6 resulted in the production of the corresponding cycloadduct with an additional oxygen molecule. A thorough, spectroscopical study (1H and 13;C NMR, COSY, DEPT, HMQC, and HMBC) allowed the structure of monocycloadduct 9 to be unambiguously unraveled as that of an endoperoxide, as a result: of the sensitizing effect: of the C60 unit, which efficiently promotes the addition of excited singlet oxygen to the diene moiety of the steroid. Cyclic voltammetry of hybrids 7-9, as well as their electronic spectra, support the exclusive formation of the corresponding monoadducts. ©2009 Wiley-VCH Verlag GmbH & Co. KGaA.