Diastereoselective Grignard reactions
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
New, chiral β-sec-amino alcohols (αR,βR)-11a-13a, (αS,βR)-11b-17b, (αS,βS)-11c, 12c, 15c, 17c and (αR,βS)-11d, 12d, 15d, 17d have been synthesized from the enantiomerically pure amine (all-R)-1a via diastereomeric, N-tert-butoxycarbonyl-protected aldehydes 3. Grignard additions proceed in fair yields with a high degree of diastereofacial stereoselection (diastereomeric ratios dr up to ≥ 95:5) with non-chelation control, generally in favor of the anti-(erythro) structures. A mechanistic interpretation of the stereochemical course of this reaction is presented. The stereodifferentiating ability of selected stereoisomeric (erythro)- and (threo)-amino alcohol structures were tested in homogeneous catalysis, e.g. in two model reactions (optical purities up to 95%).
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