We wish to report an efficient synthesis of 11-deoxy PGElg, 11-deoxy PGFlc, and ll-deoxy PGFl5 and its 158 epimers via the key intermediate 2-(6'-carbomethoxyhexyl)-cyclopenten-1-one-3-carboxaldehyde (6). Michael addition of nitromethane to the ketone 1 7a , catalyzed with tetra-2 methylguanidine , at room temperature afforded the nitroketone 2 in 84% yield3 [oil; ir 1750, 1551 cm -1 ; nmr 3.62 (s, 3H, Og3), 4.5 ppm (m, 2H, -CH2N02); m/e 254 (285-0CH3).1 Transformation of this compound into the cycloethylene ketal 2 was effected with ethylene glycol in benzene solution in the usual manner, to afford 2 in 95% yield [oil; ir 1745 (s), 1550 (s), 1360 cm-'; nmr 2.18 (broad t, J=7, CIi2 COOCH3), 3.65 (s, 3H, 0CH3), 3.89 (s, 4H, OCH,CH20), 4.25-4.58 ppm (m, 2H, -CH,N02) ; m/e (329).1 Treatment of a tetrahydrofuran solution of 3 with 0.1 N aqueous potassium hydroxide, generated the potassium nitronium salt 4 -. After removal of the organic solvent under reduced pressure, the resulting aqueous solution of 4 was buffered to pH 7 with magnesium sulfate and oxidized at 0-5OC with a dilute solution of potassium permanganatel to give 2. Esterification with diasomethane afforded the unstable aldehyde 5 [nmr 2.24 (broad t, J=7, CH2 COOCH3), 3.61 (s, 3H, OCH3), 3.90 (s, 4H, OCH2CH20), 9.6 ppm (d, J=2, lH, CH=O) 1, which, on reaction with the anion of dimethyl 2-oxoheptylphosphonate followed by zinc borohydride reduction5 , yielded a mixture of C-15 epimeric alcohols 7. -Hydrolysis of this mixture in 65% aqueous acetic acid at room temperature, yielded a 1:l mixture of carbinols 8 which was separated by chromatography on silica gel to yield the more polar 15a alcohol [ir 3470, 2960 (sh),