The acid was obtained in 52% yield as the trimethyl ester by alkaline permanganate oxidation of the methyl ether 111, followed by methylation with diazomethane. The free acid and crystalline triethyl ester also were prepared. Oxidation d the methyl ether I11 with nitric acid also was investigated. While this reagent did not prove suitable for preparing IVa, the results were of hterest. When I11 was heated with concentrated nitric acid for fifteen ...
