Chiroptical properties of binuclear rhodium complexes of lanostane alcohols

The circular dichroism (CD) of the in situ-formed Rh-2 (OCOCF3)(4) complexe s of sterically hindered, secondary lanostane alcohols was investigated. Th e main object of the present studies are derivatives of 3 beta-, 7 alpha-, 7 beta-, and 11 beta -hydroxylanostanes with or without an additional funct ional group, e.g., double bond, oxo-, hydroxy-, or acetoxy groups. Up to fi ve Cotton effects (CEs) can be found in the CD spectra of Rh-complexes of t hese alcohols in the spectral range between 650-300 nm. Correlation of the CEs signs with the absolute stereochemistry at the carbon atom bearing the hydroxy group was investigated. The Rh-complex with the 3 beta -acetoxylano stan-11 beta -ol ligand was isolated in the crystalline form. Its polymeric structure, determined by the X-ray method, shows the di-Rh-units linked by the axially ligating oxygen atoms of the hydroxy and acetoxy groups. In th e latter case, the coordination takes place through the carbonyl oxygen. Ch irality 13:313-321, 2001. (C) 2001 Wiley-Liss, Inc.