Synthesis of two (S)-indoline-based chiral auxiliaries and their use in diastereoselective alkylation reactions |
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| Institution: | 1. Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy;2. Department of Pharmaceutical and Pharmacological Sciences, University of Padova, via Marzolo 5, 35131 Padova, Italy;3. The Copper Mill Sevojno, 31000 Uzice, Serbia;4. Faculty of Science, Chemistry Department, 3400 Kragujevac, Serbia;5. CNR, Institute of Sciences and Molecular Technologies, via Marzolo 1, 35131 Padova, Italy;1. Departamento de Química Orgánica and UMYMFOR (CONICET – Facultad de Ciencias Exactas y Naturales), Universidad de Buenos Aires, Pabellón 2, Piso 3, Ciudad Universitaria, C1428EGA Buenos Aires, Argentina;2. Departamento de Química Biológica and IQUIBICEN, (CONICET – Facultad de Ciencias Exactas y Naturales), Universidad de Buenos Aires, Pabellón 2, Piso 4, Ciudad Universitaria, C1428EGA Buenos Aires, Argentina;3. Laboratorio de Glicobilogía, Fundación Instituto Leloir e Instituto de Investigaciones Bioquímicas de Buenos Aires, Avenida Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina |
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| Abstract: | Two chiral auxiliaries, 2-(S)-indolin-2-yl]propan-2-ol 1a and (S)-2-(2-methoxypropan-2-yl)indoline 1b, were synthesised from enantiomerically pure (S)-indoline-2-carboxylic acid 3. High diastereoselectivities in alkylations of enolates of the propanoylamides derived from the two auxiliaries are presented. Surprisingly, both auxiliaries induced the same selectivity at the newly created stereogenic centre. The benzyl bromide and n-butyl iodide alkylation reactions showed diastereomeric ratios that were moderate (81:19) to very good (96:4) and with very good yields (86–98%). When LiCl was used as an enolate coordinating agent, in the benzylation of the enolate from propanoylated auxiliary 1a, a very high crude diastereomeric ratio was obtained (99.7:0.3). |
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