
%0 Journal Article
%A Cambie, RC 
%A Hayward, RC 
%T Chemistry of the Podocarpaceae. XLVIII. Photo-sensitized oxidations of unsaturated ring-c aromatic diterpenoids
%J Australian Journal of Chemistry
%D 1974/09/01
%V 27
%N 9
%P 2001-2016
%K 
%R https://doi.org/10.1071/CH9742001
%U https://www.publish.csiro.au/paper/CH9742001 
%X Photo-sensitized oxidation of the 6,7-dehydro ring-c aromatic diterpenoids (5), (8) and (38) affords high yields of the corresponding 5-ene-7-ones (62), (63) and (69). Similar oxygenation of 13-methoxy- totara-6,8,11,13-triene (21) gives a hydroperoxide (74) which undergoes a facile rearrangement to a naphthyl derivative (80) in the presence of acid. Photo-sensitized oxidation of the enol acetates derived from the 7-oxo diterpenoids, however, provides a general method for preparation of the corresponding 5-ene-7-one. Reduction of the enone (62) with lithium aluminium hydridealuminium chloride gives a mixture of the 5,8,11,13-tetraene (66) and the 6,8,11,13-tetraene (9) while reduction with sodium borohydride and treatment of the resulting alcohols (61) and (67) with acid gives a mixture of the tetraenes (5) and (68). Photo-oxygenation of the latter mixture provides a convenient method for isolating the tetraene (68). Similar reductions of 13-methoxytotara-5,8,11,13-tetraen-7-one (76) have been examined and products from the action of m-chloroperbenzoic acid on the enol acetates (19), (20) and (7) are reported. 
