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OPTICAL ACTIVE 2-ARYLPROPANOIC ACIDS
1701
values were adjusted to enantiomeric excesses of 100%. All reagents and
solvents were purified and dried as required.
Synthesis of the esters (1) and (2): A mixture of (6-methoxy-2-
naphthyl) 1-propanone (2.2 g, 10 mmol) and ZnCl (1.36 g, 1 mmol) was
2
dissolved in 40 ml DMF/trimethyl orthoformate, followed by the addition
of D-mannitol (1.82 g, 10 mmol). The reaction mixture was stirred and
ꢀ
heated to 130–140 C for 3 h. The resulting solution was evaporated in
reduced pressure, the residue was extracted with methanol (20 ml) three
times and chromatographed on silica column (CH Cl : CH OH ¼ 7 0 : 30,
2
2
3
v/v); two components were obtained.
20
Esters (1): M.p. 82–84 C, [ꢀ] þ 98 (c1.8. CHCl ). MS (m/z): 397
ꢀ
ꢀ
D
3
þ
þ
1
(
(
5
1
(M ꢁ 1) , 20), 398 (M , 14), 105(15). H-NMR (ꢂ, ppm, DMF-d ): 7.4
7
m, naphthyl, 8H), 4.0 (s, 3H), 1.2 (d, 3H), 3.5 (q, 1H), 3.9–4.7(m, 6H),
1
3
.1 (s, 1H). C-NMR (ꢂ, ppm, DMF-d ): 170, 129, 127, 124, 128, 129, 126,
7
25, 130, 131, 132, 39.5, 21, 81, 78, 76, 74, 76, 78, 55. IR (KBr, cm ): 3450
ꢁ1
br, 2900, 1726, 1604, 1540, 1445, 1320, 1225, 1110, 1030, 985, 780, 685.
Anal. calcd for C H O : C, 60.9; H, 6.6. Found C, 60.7; H, 6.7.
2
0
26
8
ꢀ
20
D
ꢀ
Esters (2): M.p. 82–84 C, [ꢀ] þ 156 (c 1.8. CHCl ). MS (m/z): 598
3
þ
þ
1
(
naphthyl, 16H), 4.0 (s, 3H), 1.2 (d, 2H), 3.5 (q, 2H), 3.7–4.7 (m, 6H), 5.1 (s,
M , 14), 597((M ꢁ1) , 20), 105 (10). H-NMR (ꢂ, ppm, DMF-d ): 7.4 (m,
7
1
3
1
1
2
H). C-NMR (ꢂ, ppm, DMF-d ): 170, 129, 127, 124, 128, 129, 126, 125,
30, 131, 132, 39.5, 21, 81, 78, 76, 74, 76, 81, 55. IR (KBr, cm ): 3450 br,
900, 1726, 1604, 1540, 1445, 1320, 1225, 1110, 1030, 985, 780, 685. Anal.
7
ꢁ
1
calcd for C H O : C, 67.3; H, 6.3. Found C, 67.2; H, 6.1.
3
4
38 10
Hydrolysis of the esters (1) and (2): The residue was dissolved directly
in 40 ml methanol and 10 ml concentrated hydrochloric acid was added and
refluxed for 2 h. After being cooled to room temperature, the mixture was
neutralized by 10% NaOH solution to pH ¼ 6–7; the mixture was extracted
with CH Cl (20 ml) three times and washed with water, concentrated, and
2
2
finally chromatographed on silica column (CH Cl : CH OH ¼ 70 : 30, v/v).
2
2
3
ꢀ
A white product was obtained (1.96 g, yield: 85%). M.p. 153–155 C,
ꢀ] þ 63.2 (c 1.8. CHCl ), ee 98%; m.p. 154–156 C, [ꢀ] þ 63.5 (c 1.8.
2
0
ꢀ
ꢀ
20
D
ꢀ
[
CHCl ).
D
3
[5]
3
REFERENCES
1
. (a) Oosterom, G.E.; van Haaren, R.J.; Reek, J.N.H.; Kamer, P.C.J.; van
Leeuwen, P.W.N.M. Chem. Commun. 1999, 1119; (b) Hovestad, N.J.;
Eggeling, E.B.; Heidbuschel, H.J.; Jastrzebski, J.T.B.H.; Kragl, U.;
Keim, W.; Vogt, D.; van Koten, G. Angew. Chem. Int. Ed. 1999,
381, 1655.