version date: 1 December 2006 3D conversion active isomer r 3D conversion Propranolol(5) active isomer s Fig 4 Conformations of R-epinephrine(4)and S-propranolol (5)with distinct configuration descriptors Cahn-Ingold-Prelog priority rules), but with the stereogenic center in the same spatial disposition The importance of the shape and size of the molecule is illustrated by trans diethylstilbestrol (6)used to mimic estradiol, the natural hormone(7), Fig. 5. Comparing the interatomic distances in the natural and synthetic products, it can be seen that only the trans-isomer(6)has the desired distances between carbons containing hydroxyl groups around 9.0 A. The corresponding cis-isomer(8)shows distances of 5.9 A, quite different from the estradiol molecule(8.6A) <www.iupac.org/publications/cd/medicinalchemistry/>5 O N H OH 3D conversion Propranolol (5) active isomer S HO HO H N CH3 OH 3D conversion Epinephrine (4) active isomer R Fig. 4 Conformations of R-epinephrine (4) and S-propranolol (5) with distinct configuration descriptors (Cahn–Ingold–Prelog priority rules), but with the stereogenic center in the same spatial disposition. The importance of the shape and size of the molecule is illustrated by trans￾diethylstilbestrol (6) used to mimic estradiol, the natural hormone (7), Fig. 5. Comparing the interatomic distances in the natural and synthetic products, it can be seen that only the trans-isomer (6) has the desired distances between carbons containing hydroxyl groups, around 9.0 Å. The corresponding cis-isomer (8) shows distances of 5.9 Å, quite different from the estradiol molecule (8.6 Å).11 <www.iupac.org/publications/cd/medicinal_chemistry/> version date: 1 December 2006