A crystalline substance fromArtemisia rutifolia

New synthesis of trans,trans-2-[6-(ethoxycarbonyl)hexyl]-3-(ethoxycarbonyl)-4-hydroxycyclopentanone, a useful intermediate for the synthesis of prostaglandins

“…The target molecule (1), which may be obtained from the cyclopentenone 7 by standard methods, constitutes an interesting intermediate for the synthesis of PGj derivatives and has been used, for instance, in the Ciba-Geigy PGEi total synthesis. 3 Ethyl acetoacetate when treated with 2 equiv of ethanethiol and 1 equiv of trimethylchlorsilane4 at room temperature gives the corresponding thioketal in quantitative yield. Pyrolysis of this compound in the presence of potassium hydrogen sulfate as an acidic catalyst followed by distillation led to the thioenol ether 3 quantitatively5 (Scheme II).…”

“…Careful distillation afforded the product, bp 62 °C (0.5 mm). The product was obtained as a light yellow oil: 15 g (86%); IR (neat) 1720, 1600; NMR 5.4 (s, 1 ), 4.06 (q, 2 H), 2.8 (q, 2 H), 2.33 (s, 3 ), 1.33 (t, 3 ), 5). n-Butyllithium (1.4 M, 24 mL, 33 mmol) was added at 0 °C with stirring under argon to a solution of diisopropylamine (4.6 mL, 33 mmol) in THF (20 mL).…”

“…1750-1700 (s, br), 1600 (s); NMR (CDC13) 7.61 (dd, 1 H, Jwl = 6.0 Hz, Ju,i2 ~2. 3 Hz, Cn H), 6.25 (dd, 1 H, J10,n = 6.0 Hz, j10,i2 2.3 Hz C10 ), 4.15 (dq, 4 H), 3.52 2,3-trans :3,4-irans :4,5-cis -2-[6-(Ethoxycarbonyl)hexyl]-3-(ethoxycarbonyl)-4,5-epoxycyclopentanone (8). To a solution of 7 (1.55 g, 5 mmol) dissolved in 100 mL of methanol at -45 °C were added 30 mL of 2 N NaOH and 10 mL (40 mmol) of 30% H202.…”

“…A portion of the mixture (0.100 g) was purified by using preparative TLC with 1:3 ethyl acetate-hexane as the solvent to give pure a isomer (0.05 g). The spectral data were as follows: IR (neat) 1740; NMR 4.15 (m, 5 H, 2 CH2, C10 H), 3.4 (m, 1 H, Cn ), 3.1 (d, 1 H, C12 , =/812 = 3 Hz), 2.5 (m, 1 H, C8 H), 2.2 (t, 2 ), 1.9-1 (m, 16 H); MS, 'm/e 326 (M), 281 (M -OCH2 CH3). Anal.…”