Isopropanol → (R)-2-Ethyl-4-nitrobutanoic acid

Beteiligte Stoffe

Reaktionsschritte

To 1.0 mmol alcohol 2b dissolved in 10 mL acetone at 0° C. was added 1.5 mmol H2Cr2O7 (3 mL Jones reagent). The mixture was stirred for 5 h, during which time the mixture warmed to room temperature. Excess isopropanol was added, and the mixture was stirred for 10 min. The mixture was filtered, and the solution was diluted with 2 mL 2 N HCl and extracted with Et2O. Complete extraction of the product into the Et2O phase was monitored by TLC. The organic layers was washed with saturated NaCl, dried over MgSO4, filtered and concentrated to give a viscous oil, of which the desired product 3 was purified via column chromatography eluting with EtOAc/hexane (1:10 to 1:3; v/v) to give pure product as a yellow oil in 92% yield. TLC Rf=0.45 (EtOAc/hexanes, v/v, 1:1) 1H NMR (300 MHz, CDCl3) 4.56-4.41 (m, 2H), 2.53-2.44 (m, 1H), 2.38-2.19 (m, 2H), 1.84-1.60 (m, 2H), 1.00 (t, J=7.4 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 180.66, 73.55, 43.57, 28.41, 25.24, 11.41. HRMS m/z (ESI): calc. for C6H11NO4Na [M+Na]+184.0586, found 184.0578. Optical rotation: [α]rtD+17.51 (c=3.82, CHCl3). The ee of this compound (>95%) was determined by coupling one portion to L-Phe-OMe and another portion to D-Phe-OMe and then analyzing the products by 1H NMR spectroscopy.

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