In both exo and endo transition states, the dominant conformation of A-ring takes the chair form because its boat conformation has the severe strain repulsion between the vinyl methyl and C 3 -methylene (steroidal numbering) groups. On the other hand, the C-ring has two possible chair and boat conformations within 1.26 Kcal/mol. ... The macrocyclic enone 6 was prepared in the following way. ... Satisfactory 1 H NMR and IR properties were obtained.
