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L. FABIAN ET AL.
with dichloromethane (41 mL), filtered under gravity, and washed with dichloro-
methane; then the filtrate was washed with Na2CO3 (ss) and water. The organic layer
was dried over Na2SO4, filtered, and concentrated under reduced pressure to give the
ester.
1
Propyl cyclohexylacetate (5c). Yellow oil; H NMR (500 MHz, CDCl3): d
0.94 (m, 5H), 1.15 (m, 1H), 1.28 (m, 2H), 1.64 (m, 3H), 1.71 (m, 4H), 1.78 (m,
1H), 2.18 (d, J ¼ 7.1 Hz, 2 H), 4.02 (t, J ¼ 6.8 Hz, 3 H); 13C NMR (125 MHz, CDCl3):
d 10.4, 22.0, 26.0, 26.1, 33.0, 34.9, 42.2, 65.7, 173.2. Anal. calcd. for C11H20O2: C,
71.70; H, 10.94. Found: C, 71.69; H, 10.99.
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Propyl 3,4-dimethoxyphenylacetate (7c). Yellow oil; H NMR (300 MHz,
CDCl3): d 0.75 (t, J ¼ 7.4 Hz, 3 H), 1.46 (m, 2 H), 3.39 (s, 2 H), 3,66 (s, 3H), 3,69 (s,
3H), 3,88 (t, J ¼ 7.0 Hz, 2 H), 6.66 (d, J ¼ 10.5 Hz, 3H); 13C NMR (75 MHz, CDCl3):
d 10.4, 22.0, 40.9, 55.7, 55.8, 66.3, 111.3, 112.5, 121.4, 126.8, 148.2, 149.0, 171.8.
Anal. calcd. for C13H18O4: C, 65.53; H, 7.61. Found: C, 65.40; H, 7.80.
Representative Procedure for Preparation of a-Amino Acids Esters
(Table 2)
In a typical reaction, AMA 2:3 (498 g, 1 mol), the corresponding aminoacid
(1 mol) and alcohol (1.5–2 mol) were mixed in the provided reaction glass tube
equipped with a screw cap and magnetic agitation until a wet mixture was achieved.
The reaction mixture was irradiated with microwaves (Anton Parr Monowave 300
reactor) at 120 ꢀC for 20 min. On cooling, the mixture was diluted with chloroform
(41 mL), filtered with glass frit over celite under vacuum, and washed with chloro-
form; then the filtrate was washed with Na2CO3 (ss) and water. The organic layer
was dried over Na2SO4, filtered, and concentrated under reduced pressure to give
the ester.
L-valine propylester methanesulfonate (12c). Yellow oil; 1H NMR
(500 MHz, CDCl3): d 0.97 (t, 3H), 1.08 (d, 3H), 1.11 (d, 3H), 1.71 (m, 2H), 2.37
(m, 1H), 2.77 (s, 3H, CH3SOꢁ3 ), 4.01 (ca, 1H), 4.16 (m, 2H), 7.75–7.91 (brs, 3H);
13C NMR (125 MHz, CDCl3): d 10.3, 17.5, 18.3, 21.7, 29.3, 58.4, 67.7, 169.0. Anal.
calcd. for C9H21NO5S: C, 42.34; H, 8.29; N, 5.49. Found: C, 42.10; H, 8.40; N, 5.30.
L-valine isopropyl ester (12d). Yellow oil;1H NMR (500 MHz, CDCl3): d
0.88 (d, J ¼ 6.9 Hz, 3H), 0.96 (d, J ¼ 6.9 Hz, 3H), 1.24 (dd, J ¼ 6.4 Hz, J0 ¼ 6.2 Hz,
6H), 2.00 (dd, J ¼ 6.9 Hz, J0 ¼ 5.0 Hz, 1H), 3.22 (d, J ¼ 5.0 Hz, 1H), 5.00 (m, 1H);
13C NMR (125 MHz, CDCl3): d 17.3, 22.1, 32.4, 60.2, 68.3, 175.3. Anal. calcd. for
C8H17NO2: C, 60.35; H, 10.76; N, 8.80. Found: C, 60.20; H, 10.90.; N, 8.71.
L-glutamic acid dipropyl ester (13c). Yellow oil; 1H NMR (300 MHz,
CDCl3):d 0.82 (m, 6H), 1.54 (m, 4H), 1.72 (m, 1H), 1.96 (m, 1H), 2.34 (t, J ¼ 7.7 Hz,
Hz, 2H), 3.33 (dd, J ¼ 5.1 Hz, J0 ¼ 8.2 Hz, 1H), 3.94 (m, 4H); 13C NMR (75 MHz,
CDCl3): d 10.1, 21.7, 29.6, 30.3, 53.5, 65.8, 66.3, 172.9, 175.4. Anal. calcd. for
C11H21NO4: C, 57.12; H, 9.15; N, 6.06. Found: C, 56.96; H, 9.20; N, 6.03.