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<A NAME="RD23204ST-13">13</A>
A hexane solution of n-BuLi (83 mL, 207.0 mmol, 2.5 M. 2.1 equiv) was added carefully to anhyd DMSO (150
mL) in a 500 mL round-bottomed flask. (R)-(-)-Mandelic acid (15 g, 98.7 mmol) was added and the resulting solution was stirred
under nitrogen for 2 h. MeI (32.2 g, 227.0 mmol, 2.3 equiv) was then added and the
reaction mixture was stirred overnight, poured into H2O and extracted with Et2O. The combined ethereal layers were washed with brine, dried over anhyd MgSO4 and concentrated to afford (R)-(-)-methyl
2-methoxy-2-phenylacetate (17.8 g, 98.7 mmol, 100%). IR: νmax = 1740 cm-1. 1H NMR (400 MHz, CDCl3): δ = 3.41 (s, 3 H), 3.72 (s, 3 H), 4.78 (s, 1 H), 7,34-7.45 (m, 5 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 52.7, 57.8, 82.9, 127.6, 129.1, 129.2, 136.6, 171.6 (C=O) ppm. [α]D -113 (c 1.0, CHCl3). HPLC on ‘Chiracel OD-H’, eluting with hexane-propan-2-ol 99:1.
<A NAME="RD23204ST-14A">14a</A>
IR: νmax = 1747 cm-1. 1H NMR (400 MHz, CDCl3): δ = 1.54 (3 H, d, J = 6.9 Hz), 4.19 (1 H, q, J = 6.9 Hz), 4.53 and 4.77 (2 H, AB, J = 11.6 Hz), 5.27 and 5.28 (2 H, AB, J = 12.3 Hz), 7.39-7.45 (10, m) ppm. 13C NMR (100 MHz, CDCl3): δ = 19.2 (Me), 66.5 (CH2), 72.0 (CH2), 74.1 (CH), 127.9 (CH), 128.1 (CH), 128.3 (CH), 128.4 (CH), 128.5 (CH), 128.7 (CH),
135.9 (C), 137.7 (C), 173.0 (C=O) ppm. HRMS (FAB): m/z calcd for C17H19O3: 271.13393. Found: 271.13350 [M + 1]. [α]D -63.3 (c 1.6, CHCl3).
<A NAME="RD23204ST-14B">14b</A> The formation of racemic benzyl 2-benzyloxypropanoate has been reported previously
by photolysis of a chromium carbene complex in the presence of carbon monoxide:
Bueno AB.
Moser WH.
Hegedus LS.
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<A NAME="RD23204ST-15">15</A>
n-BuLi (3.7 mL, 9.25 mmol, 2.2 equiv) was added slowly to dry DMSO (7 mL) under nitrogen
in a dry 25 mL round-bottomed flask. 2-Hydroxy-3-methylbutanoic acid (500 mg, 4.23
mmol, 1 equiv) in DMSO (7 mL) was then added. The solution was stirred during 2 h
before MeI (630 µL, 10.16 mmol, 2.40 equiv) was added slowly. The reaction mixture
was allowed to stir overnight and H2O (50 mL) and Et2O (20 mL) were then added to the mixture. The organic phase was separated, washed
with brine, dried over Na2SO4 and concentrated under reduced pressure to afford the methyl
2-methoxy-3-methylbutanoate as a pale yellow liquid (620 mg, 100%). IR: νmax = 1750 cm-1. 1H NMR (400 MHz, CDCl3): δ = 0.86 (d, 3 H, J = 5.0 Hz), 0.88 (d, 3 H, J = 5.0 Hz), 1.96 (m, 1 H), 3.30 (s, 3 H), 3.44 (d, 1 H, J = 5.4 Hz), and 3.68 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 17.5 (Me), 18.5 (Me), 31.5 (CH), 51.4 (Me), 58.4 (Me), 95.9 (CH), 172.7 (C=O)
ppm. HRMS (EI): m/z calcd for C7H14O3: 146.09430. Found: 146.09460.
<A NAME="RD23204ST-16">16</A>
IR: νmax = 1745 cm-1. 1H NMR (400 MHz, CDCl3): δ = 0.82 (3 H, d, J = 6.9 Hz), 0.84 (3 H, d, J = 6.8 Hz), 1.99 (1 H, m), 3.61 (1 H, d, J = 5.5 Hz), 4.23 and 4.55 (2 H, AB, J = 11.7 Hz), 5.04 and 5.06 (2 H, AB, J = 12.2 Hz),7.19-7.22 (10 H, m) ppm. 13C NMR (100 MHz, CDCl3): δ = 17.8 (Me), 18.9 (Me), 31.7 (CH), 66.4 (CH2), 72.5 (CH2), 83.3 (CH), 127.8 (CH), 128.1 (CH), 128.3 (8) (CH), 128.4 (2) (CH), 128.5 (CH),
128.6 (CH), 135.9 (C), 137.8 (C), and 172.3 (C=O) ppm. HRMS (FAB): m/z calcd for C17H19O3: 299.16443. Found: 299.16406 [M + 1].
<A NAME="RD23204ST-17">17</A>
IR: νmax = 1736 cm-1. 1H NMR (400 MHz, CDCl3): δ = 1.18 (3 H, d, J = 6.2 Hz), 2.40 and 2.61 (2 H, o, AB of ABX,
J
A-B = -15.09 Hz, J
A-X = 7.52 Hz, JB-X = 5.51 Hz), 3.95 (1 H, q × q, J = 6.2, 5.51, 7.52 Hz), 4.39 and 4.45 (2 H, AB, J = 11.6 Hz), 5.04 and 5.05 (2 H, AB, J = 12.3 Hz), and 7.23-7.26 (10 H, m) ppm. 13C NMR (100 MHz, CDCl3):
δ = 19.9 (Me), 42.2 (CH2), 66.4 (CH2), 70.9 (CH2), 72.2 (CH), 127.5 (CH), 127.7 (CH), 128.2 (CH), 128.2 (5) (CH), 128.3 (CH), 128.6
(CH), 136.0 (C), 138.5 (C), 171.3 (C=O) ppm. HRMS (FAB): m/z calcd for C18H21O3 285.14907. Found: 285.14941 [M + 1].