Synlett 2003(10): 1455-1458
DOI: 10.1055/s-2003-40840
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Asymmetric Synthesis of Orthogonally Protected (2S,4R)- and (2S,4S)-4-Hydroxyornithine

Renaud Lépine, Anny-Claude Carbonnelle, Jieping Zhu*
Institut de Chimie des Substances Naturelles, CNRS, 91198 Gif-sur-Yvette Cedex, France
Fax: +33(1)69077247; e-Mail: zhu@icsn.cnrs-gif.fr;
Further Information

Publication History

Received 2 May 2003
Publication Date:
24 July 2003 (online)

Abstract

Synthesis of orthogonally protected (2S, 4R)- and (2S, 4S)-4-hydroxyornithine was reported featuring an asymmetric alkylation of N-(diphenylmethylene)glycine tert-butyl ester (6) by (5S)-N-benzyloxycarbonyl-5-iodomethyl oxazolidine (7). Double stereoselection was examined using chiral ammonium salts as phase transfer catalysts and a substrate-directed chiral induction is documented.

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We thank one of the reviews for pointing out this control experiment. This result was not unexpected, but it didn’t allow us to conclude whether the observed stereoselectivity in the presence of chiral ammonium salt was intrinsic to our substrate or was the consequence of the lack of the catalyst assistance.

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Compound 17. Rf = 0.5 (eluent: ethyl acetate/heptane = 1/4); IR (CHCl3) 3444, 3024, 2982, 1712, 1507 cm-1; 1H NMR (300 MHz, CDCl3, 293 K) δ 1.44 (s, 9 H) Hz, 1.46 (s, 9 H), 1.65-1.82 (m, 1 H), 1.93-1.98 (m, 1 H), 3.08-3.17 (ddd, 1 H, J 1 = 13.3 Hz, J 2 = 7.8 Hz, J 3 = 6 Hz), 3.36-3.42 (m, 1 H), 3.91 (m, 1 H), 4.22 (m, 1 H), 5.10 (s, 2 H), 5.26 (m,1 H), 5,39 (m, 1 H), 7,35 (m, 5 H); 13C NMR (75 MHz, CDCl3) δ 28.0, 28.3, 38.0, 46.8, 52.1, 66.9, 69.1, 82.3, 82.5, 128.1, 128.2, 128.5, 136.4, 156, 157.1, 171.6; MS (ESI) m/z 461 (M + Na); [α]D = +9.3 (c 0.9 CHCl3). Compound 18. Rf = 0.41 (eluant: ethyl acetate/heptane = 1/1); IR (CHCl3) 3445, 1783, 1717 cm-1; 1H NMR (300 MHz, CDCl3, 293 K) δ 1.45 (s, 1 H), 2.32 (m, 1 H), 2.46-2.53 (m, 1 H), 3.30 (dt, 1 H, J 1 = 15 Hz, J 2 = 6.3 Hz), 3.52-3.56 (m, 1 H), 4.23 (br d, 1 H, J = 6.8 Hz), 4.75 (br s, 1 H), 5.12-5.18 (m, 4 H), 7.36 (m, 5 H); 13C NMR (75 MHz, CDCl3) δ 28.2, 31.4, 44.6, 49.5, 67.1, 77.2, 80.7, 128.1, 128.2, 128.6, 136.2, 155.3, 156.7, 175.1; MS (EI) m/z 387 (M + Na), 403 (M + K); [α]D = -18.1 (c 0.57 CHCl3); [α]D = -22.4 (c 0.5 CHCl3). [20]