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Diastereo- and Enantioselective Synthesis of Vicinal Amino Alcohols by Oxa Michael Addition of N-Formylnorephedrine to Nitro Alkenes

โœ Scribed by Dieter Enders; Andreas Haertwig; Gerhard Raabe; Jan Runsink

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
657 KB
Volume
1998
Category
Article
ISSN
1434-193X

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โœฆ Synopsis

Michael addition / Nitro alkenes / C-O bond cleavage

The first intermolecular asymmetric oxa Michael additions cleavage of the auxiliary occurred without epimerisation (69-99%) using Na/NH 3 . The Boc-protected 2-amino alcohols with removable chirality information within the hydroxide source are reported. As enantiopure oxygen nucleophile 12a-h could be obtained in good overall yields (30-58 %, four steps) and excellent diastereomeric and enantiomeric functioning as chiral hydroxide equivalent Nformylnorephedrine (7) was used and conjugate additions to excesses (de, ee = 94-ี†98%). Transition states explaining the overall stereochemical outcome are presented based on the aliphatic (E)-nitro alkenes 2a-j were carried out in good yields (35-87%) and excellent diastereomeric excesses (de = absolute configuration determined by X-ray structure analysis on 8b. 94-ี†98%). After reduction of the nitro group and protection of the amino function (11a-h, 73-87%, both steps), the

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