(1995; 53 pages)
9.1 The rings of a steroid are depicted as a projection on to the plane of the paper. The projection should normally be oriented so that position 3 is at the bottom left and the regular pentagonal ring D at the top right, with position 17 uppermost.
9.2 A bond that lies below the plane of the paper is given the designation a and shown by a broken line; a bond that lies above the plane of the paper is designated as β and shown by a wedge, while a bond whose configuration is not known is designated as ξ and denoted by a wavy line. All the hydrogen atoms attached to centres of asymmetry are shown.
9.3 The backbone of a side-chain at C-17 is best shown as in the plane of the paper (lines of ordinary thickness), the bond between C-17 and C-20 being similarly shown. Side-chains are usually represented by lines at an angle to one another, the terminal groups being set out in full, as shown below. Stereochemistry due to substituents in the chain is indicated by the customary wedges and broken lines:
Cardenolides (see also section 8.5), bufanolides and derivatives of calciferol are depicted as shown below: