| Popis: |
Cationic cyclization of 2-[7-(3-methoxyphenyl)-(E)-3-heptenyl]-3-methyl-2-cyclopentenol (7) gave mainly tetracyclic products via Ar1-6 and/or Ar2-7 participation. The major product, 3-methoxy-17-methyl-B-homo-1,3,5(10),13(17)-gonatetraene (9), was converted in two steps into B-homoestrone methyl ether 20. High-resolution 1H NMR spectra indicated that the seven-membered ring in 9 occurs mainly in a boat-like conformation whereas in its 1-methoxy isomer 8 it occurs in an unsymmetrical twist-boat conformation. In 20, the B-ring probably occurs both in chair and boat conformations. |
