2684
T. Bunlaksananusorn, F. Rampf
LETTER
and the mixture was stirred at 80 °C for 16 h. TFE was removed and
the crude product was passed through a short silica gel column with
tert-butylmethylether (TBME) as an eluent. After evaporation of
the solvent, (S)-5a was obtained in 88% yield, 98% ee as a white
solid; mp10 86–87 °C. 1H NMR (400 MHz, CDCl3): d = 7.35–7.15
(m, 5 H), 5.97 (br s, 3 H), 4.40 (dd, J = 8.6, 5.1 Hz, 1 H), 4.05 (q,
J = 7.1 Hz, 2 H), 2.77 (dd, J = 16.4, 8.6 Hz, 1 H), 2.67 (d, J = 16.4,
5.1 Hz, 1 H), 1.89 (s, 3 H), 1.15 (t, J = 7.1 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): d = 175.2, 170.5, 141.0, 127.7, 126.9, 125.5,
59.8, 51.3, 41.2, 20.7, 13.1 ppm.
Armstrong, J. D. III; Sun, Y.; Grabowski, E. J. J.; Volante,
R. OMCOS-13, Poster, Geneva, Switzerland, 2005.
(c) Kazuhiko, M.; Xiaoyong, Z.; Takao, S. Eur. Pat. Appl.
EP 1386901, 2004.
(4) (a) Tararov, V. I.; Börner, A. Synlett 2005, 203.
(b) Kadyrov, R.; Riermeier, T. H. Angew. Chem. Int. Ed.
2003, 42, 5472. (c) Tararov, V. I.; Kadyrov, R.; Riermeier,
T. H.; Fischer, C.; Börner, A. Adv. Synth. Catal. 2004, 346,
561. (d) Tararov, V. I.; Kadyrov, R.; Riermeier, T. H.;
Börner, A. Adv. Synth. Catal. 2002, 344, 200.
(e) Riermeier, T. H.; Haack, K.-J.; Dingerdissen, U.; Börner,
A.; Tararov, V. I.; Kadyrov, R. Ger. Offen. DE 19933611,
2001. (f) Kadyrov, R.; Riermeier, T. H.; Dingerdissen, U.;
Tararov, V. I.; Börner, A. J. Org. Chem. 2003, 68, 4067.
(5) For (+)-ClMeOBIPHEP, see: (a) Laue, C.; Schroeder, G.;
Arlt, D. Eur. Pat. Appl. EP 749973, 1996. (b) Drießen-
Hölscher, B.; Kralik, J.; Agel, F.; Steffens, C.; Hu, C. Adv.
Synth. Catal. 2004, 346, 979. (c) Gerlach, A.; Scholz, U.
Speciality Chemicals Magazine 2004, 24, 37. (d) Rampf, F.
Proc. Chiral USA 2004, Scientific update, Mayfield, UK.
(6) Using solvents such as EtOH, THF, CH2Cl2 or toluene led to
the recovered starting material 2a.
(7) For the reduction of b-keto esters, see: (a) Noyori, R.
Asymmetric Catalysis in Organic Synthesis; John Wiley and
Sons: New York, 1994. (b) Ojima, I. Catalytic Asymmetric
Synthesis; VCH: Weinheim, 2000. (c) Tang, W.; Zhang, X.
Chem. Rev. 2003, 103, 3029. (d) Blaser, H.-U.; Pugin, B.;
Spindler, F. J. Mol. Catal. A: Chem. 2005, 231, 1.
(e) Ratovelomanana-Vidal, V.; Girard, C.; Touati, R.;
Tranchier, J. P.; Hassine, B. B.; Genêt, J. P. Adv. Synth.
Catal. 2003, 345, 261; and reference therein.
References
(1) (a) Enantioselective Synthesis of b-Amino Acids; Juaristi, E.,
Ed.; Wiley-VCH: New York, 1997. (b) Gademann, K.;
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(9) The structure of ammonium salts of b-amino esters 5 were
confirmed by 1H NMR.
(10) Leflemme, N.; Dallemagne, P.; Rault, S. Synthesis 2002,
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Synlett 2005, No. 17, 2682–2684 © Thieme Stuttgart · New York