Sodium Hydroxide → HCID 68016188, compound

Participants

Reaction Steps

Conjugated malonate 3a (0.5 g, 1.5 mmol, from a 5% stock solution in methanol) was incubated with 375 Units Pig Liver Esterase (Sigma-Aldrich) in 100 mM potassium phosphate buffer pH 7.5, at 25° C. and with constant stirring. After 20 h of incubation the pH of the reaction mixture was set to 9 with 30% NaOH followed by incubation at room temperature for 30 min with constant stirring. The reaction mixture was then extracted 3 times with 250 ml tert-butyl methyl ether. The organic phase was washed twice with 125 ml deionized water and once with saturated NaCl solution, dried over Na2SO4 and finally evaporated under reduced pressure at 45° C. 0.4 g of conjugated malonate 3a were recovered. The pH of the aqueous phase left from the basic (pH 9) extraction was set to 3 with conc. HCl. Extraction with tert-butyl methyl ether, washing with water and saturated NaCl, drying over Na2SO4, filtration and evaporation under reduced pressure at 45° C. gave 62 mg (13%) of deconjugated half malonate 1a as colorless oil and E/Z 72:28 according to NMR. The suppression of byproduct 1b depends on the quality of the PLE employed, with aged PLE (>1 year) giving exclusively isomer 1a. Analytical data of the E-isomer: 1H-NMR (400 MHz, CDCl3): δ 0.96 (s, 6 H), 1.56 (3 H), 1.67 (s, 3 H), 1.4 (2 H), 1.5 (2 H), 1.9 (2 H), 2.0 (4 H), 3.6 (s, 3 H, OMe), 4.2 (d, 1 H), 5.4 (d, 1 H) ppm. 13C-NMR (400 MHz, CDCl3): δ 16.4 (q), 19.1 (t), 19.6 (q), 27.2 (t), 28.4 (2 q), 32.3 (t), 34.6 (s), 39.3 (t), 39.7 (t), 50.9 (d), 52.2 (q), 116.3 (d), 126.8 (s), 136.3 (s), 141.0 (s), 169.1 (s), 169.6 (s). Configuration of the E/Z isomers determined by NMR-analysis on a freshly prepared solution of 1a in DMSO-D6: COSY, HSQC, HMBC and NOESY.

Provenance & Evidence