3936
C. Barbieri et al. / Tetrahedron: Asymmetry 10 (1999) 3931–3937
under nitrogen. The ethanol was distilled off in a stream of nitrogen and the solid residue was re-dissolved
in dry dioxane (15 ml). The mixture was heated at reflux and the epoxide 4 (1.5 g, 7.9 mmol), dissolved
in dry dioxane (5 ml), was added in 10 min. The reaction was refluxed for 3 h. NaOH (0.15 g, 3.9
mmol) in water (10 ml) was then added and dioxane was distilled off. The residue aqueous solution
was acidified with conc. HCl (1.1 ml) and extracted with CH2Cl2 (2×20 ml). No heating was required
to induce decarboxylation. The crude extract was purified by SiO2 chromatography using as eluent a
mixture of n-hexane and ethyl acetate so as to obtain pure 5 (1.2 g, 5.2 mmol, 65% yield), mp 67°C,
[α]D=+11.5 (c 1, MeOH) and +18.6 (c 1, CHCl3), ee 95% (GC, Chirasil-dex CB); 1H NMR: δ 2.06–2.27
(1H, CH2, m), 2.60–2.70 (3H, 2CH2, m), 5.45 (1H, CH, m), 7.17 (1H, Ph, m) and 7.41–7.50 (2H, Ph, m).
Anal calcd for C10H8Cl2O2: C, 51.98; H, 3.49; Cl, 30.68. Found: C, 51.95; H, 3.42; Cl, 30.62.
3.8. (5S)-(3,4-Dichlorophenyl)dihydrofuran-2-one 10
In a 5 l beaker containing tap water (2 l) at 37°C D-glucose (100 g) was dissolved and fresh baker’s
yeast (500 g) (Distillerie Italiane, Eridania group) was added portionwise. The mixture was stirred for
30 min. The hydroxy acid 923 (5 g, 20.3 mmol) dissolved in EtOH (50 ml) was added in 15 min to the
fermenting yeast and the mixture was stirred at 25°C for 48 h. The reaction medium was filtered over a
pad of Celite® and the aqueous phase was extracted with ethyl acetate (3×250 ml). The collected organic
phases, once dried and evaporated, gave a thick oil which was purified on SiO2 chromatography using
as eluent a mixture of n-hexane and ethyl acetate so as to obtain pure 9 (1.4 g, 6.1 mmol, 30% yield),
white solid, mp 65°C, [α]D=−12.1 (c 1, MeOH), ee 98% (GC, Chirasil-dex CB); 1H NMR: δ 2.08–2.27
(1H, CH2, m), 2.61–2.73 (3H, 2CH2, m), 5.45 (1H, CH, m), 7.16 (1H, Ph, m) and 7.41–7.52 (2H, Ph, m).
Anal calcd for C10H8Cl2O2: C, 51.98; H, 3.49; Cl, 30.68. Found: C, 51.98; H, 3.47; Cl, 3.70.
Acknowledgements
We thank Mrs. Rosanna Bernardi for the GC chiral analysis. This work is partially financed by CNR
(Target Project on Biotechnology) and M.U.R.S.T., COFIN (Rome).
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