Chloroform → (-)-Acetic acid cis-4-tert-butyloxy-cyclopent-2-enyl ester

Cis-4-tert-butyloxy-cyclopent-2-enol (485 mg, 3.1 mmol, prepared in example 9) is dissolved in tert-butyl methyl ether (8.6 mL, anhydrous). To the solution is added triethylamine (0.7 eq), pancreatin (3 wt eq, available from Sigma Chemical Company), and vinyl acetate (5 eq). The reaction is allowed to stir for 17 hours at room temperature. The reaction is then filtered through diatomaceous earth and the filtrate is concentrated under vacuum. The products are separated by chromatography on silica gel (10% to 20% ethyl acetate/hexane) to provide (-)-acetic acid cis-4-tert-butyloxy-cyclopent-2-enyl ester (B, 50% yield, 76% ee), [α]D =-10.90, (c=0.98, chloroform), 1H NMR (CDCl3) δ 5.94 (d, 1 H, J=5.5 Hz), 5.89 (d, 1 H, J=5.5 Hz), 5.46 (appt, 1 H, J=5.5 Hz), 4.52 (appt, 1 H, J=5.5 Hz), 2.8 (m, 1 H), 2.0 (s, 3 H), 1.6 (d appt, 1 H, J=4.8, 14 Hz), 1.22 (s, 9 H); 13C NMR (CDCl3) δ 171.2, 138.6, 131.6, 77.4, 77.2, 41, 28.7, 28.6, 21.4; IR (neat) νmax 2976, 1738, 1364, 1242, 1196, 1067, 1020 cm-1 ; CIMS m/e (% relative intensity) 199 (M+H+, 4), 139 (M+H+ --AcOH, 70), 83 (100), and (-)-cis-4-tert-butyloxy-cyclopent-2-enol (A, 194 mg, 40% yield, >98% ee), [α]D =-17.2°, (c=1.09, chloroform) as a yellow oil.

1. filtrationThe reaction is then filtered through diatomaceous earth
2. concentrationthe filtrate is concentrated under vacuum
3. customThe products are separated by chromatography on silica gel (10% to 20% ethyl acetate/hexane)

ORD-Eintrag

ord-76f1bdeec8094cc9968de3287c4e1192

Quelldatensatz

uspto-grants-1998_09

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US05808112