| 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 Spirocoleons X-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. |
