Synlett, Inhaltsverzeichnis Synlett 2017; 28(18): 2483-2488DOI: 10.1055/s-0036-1589080 letter © Georg Thieme Verlag Stuttgart · New YorkChiral Phosphinyl Enamines and Their Asymmetric Reduction through Group-Assisted Purification Chemistry Leading to Enantiopure β-Amino Esters/Amides Autoren Institutsangaben Shuo Qiao a Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA eMail: guigen.li@ttu.edu Jianbin Wu a Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA eMail: guigen.li@ttu.edu b Institute of Chemistry and Biomedical Sciences (ICBMS), Nanjing University, Nanjing 210093, P. R. of China Junming Mo a Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA eMail: guigen.li@ttu.edu Preston T. Spigener a Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA eMail: guigen.li@ttu.edu Brian Nlong Zhao c Shanghai High School International Division, No. 989, Baise Road, Shanghai 200231, P. R. of China Bo Jiang* a Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA eMail: guigen.li@ttu.edu d School of Chemistry and Materials Science, Jiangsu Normal University, Xuzhou 221116, P. R. China eMail: jiangchem@jsnu.edu.cn Guigen Li* a Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA eMail: guigen.li@ttu.edu b Institute of Chemistry and Biomedical Sciences (ICBMS), Nanjing University, Nanjing 210093, P. R. of China Artikel empfehlen Abstract Artikel einzeln kaufen(opens in new window) Alle Artikel dieser Rubrik(opens in new window) Abstract A series of new chiral N-phosphinyl β-enamino esters and amides were successfully prepared with excellent Z-stereoselectivity (Z/E > 99:1 in nearly all cases). Group-assisted purification chemistry proved to be an efficient method for the asymmetric reduction of the resulting β-enamino esters/amides to give enantiopure β-amino esters/amides. The asymmetric reduction can be controlled efficiently by using a combination of sodium cyanoborohydride and acetic acid. Key words Key wordsgroup-assisted purification - asymmetric reduction - amino esters - amino amides - phosphinyl enamines Volltext Referenzen References and Notes 1a An G. Seifert C. Li G. Org. Biomol. Chem. 2015; 13: 1600 1b Zhang HW. Bing Y. Yang Z. Lu H. Li G. J. Org. Chem. 2016; 81: 7654 1c Seifert C. Pindi S. Li G. J. Org. Chem. 2015; 80: 447 2 Wu J. An G. Lin S. Xie J. Zhou W. Sun H. 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Ed. 2008; 47: 9337 23 Phosphinyl Enamines 2; General Procedure A mixture of phosphinamide P3 (200 mg, 0.74 mmol) , β-keto ester 1 (2.21mmol), 4 Å MS (50 mg), and TsOH (5.0 mg) in toluene (3.0 ml) was heated in a sealed vial for 10 h at 100 °C until the limiting reactant was consumed (TLC). The mixture was then filtered, diluted with EtOAc (5 mL), washed with sat. aq NaHCO3 and brine, and evaporated to dryness. The residue was purified by flash chromatography [silica gel, EtOAc–hexane (1:3)]. The eluting solvents were combined and evaporated under vacuum to afford the phosphinyl enamide as a yellow oil. All new compounds were characterized by spectroscopy (31P, 1H, and 13C NMR). Ethyl (2Z)-3-{[(2S,5S)-1-Oxido-2,5-diphenylphospholan-1-yl]amino}but-2-enoate (2c) Yellow oil; yield: 277 mg (98%). 1H NMR (400 MHz, CDCl3): δ = 9.78 (d, J = 16.2 Hz, 1 H), 7.37–7.25 (m, 10 H), 4.59 (s, 1 H), 4.14 (q, J = 5.7 Hz, 2 H), 3.68–3.58 (m, 1 H), 3.18–3.12 (m, 1 H), 2.51–2.32 (m, 2 H), 2.16–2.08 (m, 2 H), 1.42–1.39 (m, 3 H), 1.27 (t, J = 5 Hz, 3 H). 31P NMR (162 MHz, CDCl3): δ = 51.8. Ethyl (3S)-3-{[(2S,5S)-1-Oxido-2,5-diphenylphospholan-1-yl]amino}butanoate White solid; yield: 88 mg (76%); mp 186–198 °C , [α]25 D –55.2 (c 0.36, CH2Cl2); 1H NMR (400 MHz, CDCl3): δ = 7.44–7.08 (m, 10 H), 4.01–3.92 (m, 2 H), 3.52–3.50 (m, 1 H), 3.37–3.29 (m, 1 H), 3.06–2.95 (m, 1 H), 2.65 (t, J = 11 Hz, 1 H), 2.36–2.28 (m, 2 H), 2.55–2.42 (m, 2 H), 2.14–2.39 (m, 1 H), 2.08–2.02 (m, 1 H), 1.20 (t, J = 6.0 Hz, 3 H), 0.70 (t, J = 3.0 Hz, 3 H). 31P NMR (162 MHz, CDCl3): δ = 53.4; HRMS (TOF-ES+): m/z [M + H]+ calcd for C22H29NO3P: 386.1880; found: 386.1879. 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