Synlett 2011(16): 2415-2419  
DOI: 10.1055/s-0030-1261235
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Asymmetric Synthesis of Novel Biaryl Analogues with a Fused Chiral Bicyclic Bridge Using α-Amino Acids as Chiral Sources

Hong-Wu Zhao*a, Xiao Qina, Jin Cuia, Shi Sua, Xiu-Qing Songa, Hai-Long Lia, Hong Yana, Ru-Gang Zhonga, Ning-Bo Gongb, Yong-Hui Guob, Yang Lvb
a College of Life Science and Bio-engineering, Beijing University of Technology, Beijing 100124, P. R. of China
Fax: +86(10)67396200; e-Mail: hwzhao@bjut.edu.cn;
b Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, P. R. of China
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Publikationsverlauf

Received 10 July 2011
Publikationsdatum:
13. September 2011 (online)

Abstract

A series of biaryl anologues with a fused bicyclic bridge were synthesised in a diastereoselectivity of up to 14:86 via an intramolecular cyclisation of an in situ generated N-acyliminium ion. The absolute configuration of products 9b-d and 10b-d was clearly defined by a combination of X-ray crystal-structural analysis, NOE difference, and CD experiments.

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General Procedure for the Cyclisations of Compounds 8b-d
To a well-stirred solution of compound 8b-d (1.0 equiv)in anhyd acetonewas added TsOH (0.5 equiv) in one portion. The resulting reaction solution wa s stir red at r.t. for 2-4 h. The reaction solution was concentrated under reduced pressure, and the crude products were purified with column chromatography on silica gel to afford 9b-d and 10b-d, individually.
Analytical Data of (2 R )-9b
Mp 75-77 ˚C; [α]D ²³ -155.5 (c 1.0, CHCl3). ¹H NMR (400 MHz, CDCl3): δ = 7.89 (dd, J = 7.6, 1.2 Hz, 1 H), 7.72-7.82 (m, 2 H), 7.29-7.49 (m, 5 H), 6.33 (br, 1 H), 4.21 (br, 1 H), 1.82 (br, 3 H), 1.58 (br, 9 H). ¹³C NMR (100 MHz, CDCl3): δ = 169.1, 154.2, 133.5, 132.1, 130.7, 128.7, 128.7, 127.4, 126.4, 124.1, 123.6, 122.8, 81.6, 70.3, 55.0, 29.6, 28.3, 18.5, 16.9. ESI-HRMS: m/z calcd for C21H23N2O3 [M + H+]: 351.1700; found: 351.1703. HPLC: t R = 13.0 min [Chiralpak OD-H (25 cm × 0.46 cm), Daicel Chemical Ind., Ltd., hexane-i-PrOH (50:1), 1.0 mL/min, >99% ee].

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C27H26N2O3, M = 426.52, orthorhombic, a = 9.920 (7), b = 11.644 (3), c = 19.686 (6) Å, V = 2273.9 (18) ų, T = 293 K, space group P212121, Z = 4, 4035 reflections measured, 3686 unique (R int = 0.033) which were used in all calculations. The final R1 = 0.0318 with wR2 = 0.0838. The X-ray crystallographic data of compound (2S,12bS,M)-9d was deposited at the Cambridge Crystallographic Data Centre (CCDC-773497).