2198
J. Am. Chem. SOC.1982, 104, 2198-2208
1085 cm-I; 'H NMR (acetone-&) 6 0.90 (3 H, t, CH3), 1.1-2.45 (20 H, m), 4.05 (3 H, m, CHOH), 5.10 (4 H, s, OH), 5.2-5.7 (4 H, m, olefinic H); mass spectrum, m / z 336 (M - 18), 318,264; [ ( Y ] ~ +23.8' ~ L J (THF; c 0.80) [lit." +23.5' in THF]. This material proved to be in all respects identical with an authentic sample24of PGF,,. Characterization of the second compound (the faster running band in the preparative tlc plate) presumably 15-epi-PGFk was not undertaken. (b) By Wittig Coupling of 41 with 43. To a solution of 31 (0.3 g; prepared as described above) in methylene chloride (5 mL) was added dihydropyran (1 .O mL) together with anhydrous p-toluenesulfonic acid (- 10 mg). The mixture was stirred at 20 O C until TLC analysis indicated that no starting material was present (1 h). The solution was then washed with saturated sodium bicarbonate solution and evaporated to dryness to give essentially pure 43 as a viscous oil (0.4 g). TLC analysis (SiOl; Et2O; Rf0.3) showed the presence of only one spot. This material was used as follows. A solution of the (S)-(+)-phosphonium salt 41 (0.8 g) in dry tetrahydrofuran (10 mL) was cooled to -78 OC under N, and treated with 2 equiv of butyllithium in ether (2.4 mL solution). The temperature was allowed to rise to -20 OC and then after 30 min was lowered again to -78 'C. To this solution there was added during 7 min a solution of 43 (0.4 g) in tetrahydrofuran (5 mL). The temperature was allowed to rise to 0 'C and, after a further 30 min at room temperature, the solvent was removed under reduced pressure at
