Reactions of podocarpic acid derivatives with thallium(III) nitrate

Article abstract of DOI:10.1021/jo00300a016

The reaction of methyl O-methyl-7-ketopodocarpate (3) with thallium(III) nitrate in acetic acid was performed in attempt to synthesize compound 4, an intermediate in the total synthesis of the plant growth hormone gibberellic acid. The reaction unexpectedly resulted in new methodology for the one-step formation of methyl O-methyl-Δ^5,6-7-ketopodocarpate from the keto ester 3. Four model compounds, having similar skeletons to the keto ester 3, were reacted with TTN under the same conditions to establish a general method for the formation of α,β-unsaturated ketones. These models yielded either the α-nitrato ketone and/or the decomposition product benzoic acid. Reaction of the hindered tricyclic ketone 11 with TTN yielded the expected α,β-unsaturated ketone 12. Thus this methodology is selective for hindered tricyclic ketone systems.