Abstract
Spirocoleons: Synthesis and Characterization of Four Diastereomeric Spiro (methylcyclopropane) Substructures; Revision of the Configuration at C(12) and C(15) of Coleon P and Derivatives and Coleon‐Z Derivatives; X‐Ray Analysis of Lanugon J and of Further SpirocoleonsX‐ray analyses show the correctness of the previously published structure of coleon Q (1), establish the structure of lanugon J (4a), and necessitate a revision of the configuration at C(12) and C(15) in coleon P (3a) and its derivatives 3b and 3c, and furthermore of the coleon Z derivatives 11a–11d. Two further diastereomeric spiro (methylcyclopropane) substructures have been generated by photoisomerization of lanugon J (4a) and 12‐O‐desacetylcoleon N (8); they represent the novel cis‐type B with (12R, 13R, 15S)‐ and the novel trans‐type D with (12R, 13R, 15R)‐configuration (Scheme 1). The structures of the photoproducts 5a ((12R, 13R, 15R)‐lanugon J) and 7a ((12R, 13R, 15S)‐lanugon J) were established by X‐ray analysis. So far, only two of the eight possible diastereomers of the spiro‐(methylcyclopropane) substructure I have been detected in nature, i.e. the trans‐type A with (12R, 13S, 15S)‐ and the cis‐type C with (12R, 13S, 15R)‐configuration. The four diastereomers A‐D, all possessing (12R)‐configuration, show very similar properties. However, careful comparison of spectral and chiroptical data allow a differentiation, even in the case of functionalization of H3C(17). The (12S)‐counter‐parts could not yet be prepared.
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