For compounds 1-5 and 8 (with the C ring in the boat or chair conformation), the A ring is very close to a chair conformation, since for all cases Q . ± q3 = 0.535-0.542 D and q2 . 0.018- 0.042 D. In addition, 2 = 175-178º and the displacements relative to the mean plane are given by Z1= -Z2 = +Z3 = -Z4 = +Z5 = -Z6. The f2 value for this ring is 230-280º, which indicates that the ring is slightly distorted from the pure chair in the direction of a twist boat conformation, and hence is flattened in the C-4/C-5/C-10 moiety.