Chiroptical properties of binuclear rhodium complexes of lanostane alcohols

The circular dichroism (CD) of the in situ‐formed Rh2(OCOCF3)4complexes of sterically hindered, secondary lanostane alcohols was investigated. The main object of the present studies are derivatives of 3β‐, 7α‐, 7β‐, and 11β‐hydroxylanostanes with or without an additional functional group, e.g., double bond, oxo‐, hydroxy‐, or acetoxy groups. Up to five Cotton effects (CEs) can be found in the CD spectra of Rh‐complexes of these 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 3β‐acetoxylanostan‐11β‐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 the latter case, the coordination takes place through the carbonyl oxygen. Chirality 13:313–321, 2001. © 2001 Wiley‐Liss, Inc.