Simple and inexpensive threonine-based organocatalysts for the highly diastereo- and enantioselective direct large-scale syn-aldol and anti-Mannich reactions of α-hydroxyacetone

Simple and inexpensive threonine-based organocatalysts that promote syn-aldol reactions and three-component asymmetric anti-Mannich reactions of alpha-hydroxyacetone achieving a respectable level of enantioselectivities are reported. The syn-aldol products could be obtained with up to a 99:1 syn/anti ratio and > 99% ee while the anti-Mannich products could be obtained with up to a 96:4 anti/syn ratio and > 99% ee. Catalyst 1c can be used efficiently on a large-scale with the enantioselectivities of the syn-aldol and anti-Mannich reactions being maintained at the same level, which offers a great possibility for application in industry. (C) 2011 Elsevier Ltd. All rights reserved.