Studies Directed toward the Synthesis of the Unusual Antileukemic Diterpene Jatrophatrione. 2. Functionalization of Advanced Polycyclic Precursors to the 9-Epi and 8,9-Dehydro Congeners.
The synthesis of highly functionalized [5.9.5]tricyclic systems closely related to jatrophatrione (1) and 9-epijatrophatrione (2) is described. The first set of experiments provides a route to the conjugated 7-methylene ketones 8 and 9, both of which resist migration of the exocyclic double bond to a position internal to the ring. Subsequent dihydroxylation studies define a convenient pathway from 3 to triketone 20, which has yet to exhibit a tendency to undergo appropriate dehydration at the tertiary carbinol center. The presence of a carbonyl group in ring C was shown not to be contributory to this low reactivity. Finally, a protocol involving formation of a bromo oxetane with subsequent introduction of a C8-C9 double bond and Grob fragmentation has shown promise for arrival at 1 and/or 2 by making available the diene 36.
Paquette
Leo A.
LA
Evans Chemical Laboratories, The Ohio State University, Columbus, Ohio 43210, and Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487.
Edmondson
Scott D.
SD
Monck
Nathaniel
N
Rogers
Robin D.
RD