960
H. Yang et al. / Tetrahedron: Asymmetry 10 (1999) 957–960
ester (S)-(+)-1: 42 mg, 0.24 mmol, 36% yield, 67% ee, [α]D22=+24.9, c=1.19, EtOH); remaining 1-
phenylethanol (S)-(−)-3: 33 mg, 0.27 mmol, 41% yield, >98% ee, [α]D22=−40.8, c=1.3, MeOH.
0
1H NMR (250.1 MHz; CDCl3) 4: δ 1.48 (3H, d, J1 ,2 =6.6, 2 -H), 1.49 (3H, d, J2,3=7.2, 3-H), 3.75
0
0
(1H, q, J2,3=7.2, 2-H), 5.85 (1H, q, J1 ,2 =6.6, 1 -H), 7.06–7.31 (10H, m, Ph–H); 13C NMR (62.9 MHz;
CDCl3): δ 18.47 (3-C), 22.48 (20-C), 45.86 (2-C), 72.59 (10-C), 125.80, 127.16, 127.73, 128.42, 128.66,
140.57, 141.81 (Ph–H), 173.67 (1-C); IR (KBr): 2960 m, 1725 s, 1325 m, 1190 s, 1160 s, 1045 m, 740
m, 680 s. Anal. calcd for C17H18O2: C 80.28, H 7.13, found: C 80.21, H 7.21.
0
0
0
3.6. Synthesis of (R)-2-phenylbutyric acid-(R)-1-phenethyl ester 5
Following the above general procedure, 70 mg (0.26 mmol, 40% yield, >98% ee (alcohol), 56% de
(1H NMR, [α]D22=+23.8, c=1.38, CHCl3) of (R,R)-5 was isolated as a colorless liquid after 35 h reaction
time. Remaining vinyl ester (S)-(+)-2: 50 mg, 0.26 mmol, 41% yield, 58% ee, [α]D22=+14.9, c=1.35,
CHCl3); remaining 1-phenylethanol (S)-(−)-3: 31 mg, 0.25 mmol, 39% yield, 94% ee, [α]D22=−36.8,
c=1.1, MeOH.
1H NMR (500.1 MHz; CDCl3) 5: δ 1.06 (3H, t, J3,4=7.4, 4-H), 1.10 (3H, t, J3,4=7.3, 4-H), 1.63 (3H, d,
0
0
0
0
0
0
J1 ,2 =6.7, 2 -H), 1.71 (3H, d, J1 ,2 =6.5, 2 -H), 1.98–2.34 (2H, m, 3-H), 3.69 (1H, m, 2-H), 6.06 (1H, q,
J1 ,2 =6.6), 7.31–7.53 (10H, m, Ph–H); 13C NMR (125.8 MHz; CDCl3): ·12.54 (4-C), 22.36, 22.75 (20-
C), 26.90, 27.07 (3-C), 54.02, 54.09 (2-C), 72.78, 72.90 (10-C), 126.10, 126.42, 127.47, 127.50, 127.95,
128.17, 128.38, 128.46, 128.69, 128.83, 128.86, 128.89, 139.38, 139.51, 142.04, 142.10 (Ph–C), 173.72,
173.72 (1-C); IR (KBr): 2950 m, 2910 m, 1740 s, 1485 m, 1445 m, 1190 s, 1150 s, 1050 s, 1015 m, 740
m, 680 m. Anal. calcd for C18H20O2: C 80.56, H 7.51, found: C 80.42, H 7.53.
0
0
Acknowledgements
The authors are grateful for a grant by the German Research Foundation (DFG, Bonn, Germany) and
a postdoctoral stipend for Dr. Hong Yang provided by the Alexander v. Humboldt Foundation (Bonn,
Germany). We thank Prof. W. A. König (University of Hamburg, Germany) for providing the column
for chiral analysis by gas chromatography and Prof. R. D. Schmid (Institute for Technical Biochemistry,
University of Stuttgart, Germany) for useful discussions.
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