Absolute configuration of C20H30O6Si, a species with a (1R,5R)-8-oxabicyclo[3,2.1]octa-2,6-diene core produced selectivity by the rhodium(II) octanoate catalyzed decomposition of a chiral vinyldiazomethane in the presence offuran

The compound under investigation crystallizes in the noncentrosymmetric mon oclinic space group P2(1) with a = 9.1798(23), b = 6.6606(18), c = 17.6591( 41) Angstrom, beta = 94.342(20)degrees and Z = 2. The C20H30O6Si molecule c ontains three chiral centers tone of which is of known configuration, based upon an (R)-pantolactone auxiliary group). We have determined the absolute configuration of this species (via the anomalous dispersion of Si relative to C and O) and show that it is consistent with the known configuration of the (R)-pantolactone moiety.