A solution of 1.72 g. of 7-[8-nitromethyl-7-(3-oxo-1-octenyl)-1,4-dioxaspiro[4.4]non-6-yl]-5-heptenoic acid in 80 ml. of tetrahydrofuran was treated at -10° C. with 9.7 ml. of 3M methyl magnesium bromide in tetrahydrofuran and was stirred at 0° C. for one hour. The reaction mixture was added to aqueous ammonium chloride solution, acidified with acetic acid and extracted with ether. After washing with water and drying over magnesium sulfate, the extract was evaporated and the residue chromatographed on silica. Elution with 30% ethyl acetate in hexane gave 0.26 g. of the title product as an oil, λmaxfilm 3.00 (shoulder), 3.45, 5.80 (shoulder), 5.85, 6.45, 7.25, 10.30 μ. NMR: δ 1.32 (S, 15-methyl), 4.01 (S, 4, ketal), 4.40 (M, 2, CH2NO2), 5.22 (M, 2, 5 and 6--H), 5.63 (M, 2, 13 and 14--H) ppm. Mass spectrum: M+ at m/e 453), (theory 453), M+ --H2O at m/e 435.2571 (theory 435.2620).
