Dibothrioclinin I and II, epimers from Gerbera piloselloides (L.) Cass

Dibothrioclinin I and II, namely (+)-(11R,12S,25R,27S)- and (+/-)-(11RS,12RS,25RS,27SR)-3,3,7,17,21-pentamethyl-4,12,18,26-tetraoxaheptacyclo[15.11.1.0(2,15).0(5,14).0(6,11).0(19,28).0(20,25)]nonacosa-5(14),6,8,10,19(28),20,22,24-octaene-13,27-dione, respectively, are C(30)H(28)O(6) epimers which are derived from two bothrioclinin moieties joined so as to create an additional six-membered ring. Structurally, the epimers differ only by inversion at one C atom of a central ring junction and the corresponding six-membered rings have similar conformations in each molecule, except for one ring adjacent to this inversion site.