[reaction: see text] L-Proline-based small peptides have been developed as efficient catalysts for the asymmetricdirectaldolreactions of hydroxyacetone with aldehydes. Chiral 1,4-diols 7, which are disfavored products in similar aldolreactions catalyzed by either aldolases or L-proline, were obtained in high yields and enantioselectivities of up to 96% ee with peptides 3 and 4 in aqueous media.
[reaction: see text] The catalytic activity of the prolinamide-type catalysts may be improved by introducing additional prolinamide moiety into the catalyst, while the enantioselectivity can still be maintained or further improved. A C2-symmetric bisprolinamide with two prolinamide moieties has been found to be an excellent catalyst for directaldolreaction with more than doubled reactivity and better
Additive-controlled regioselective direct asymmetric aldol reaction of hydroxyacetone and aldehyde
作者:Ling-yan Liu、Bing Wang、Yunna Zhu、Wei-xing Chang、Jing Li
DOI:10.1016/j.tetasy.2013.03.018
日期:2013.5
developed for the directasymmetricaldolreaction of hydroxyacetone and various aldehydes with moderate to high yields and high enantioselectivities. More importantly, this regioselective reaction could be easily regulated by changing the additives in the presence of the same organocatalyst 1b, to afford the normal 1,2-diol adducts and the disfavoured 1,4-diol products, respectively, in a highly regioselective
Organocatalyzed direct aldol condensation using l-proline and BINAM-prolinamides: regio-, diastereo-, and enantioselective controlled synthesis of 1,2-diols
作者:Gabriela Guillena、María del Carmen Hita、Carmen Nájera
DOI:10.1016/j.tetasy.2006.03.023
日期:2006.4
Recoverable BINAM-prolinamide derivatives, as well as L-proline, give results complementary to antibodies when used as organocatalysts for aldol reactions between aldehydes and alpha-alkoxyacetones driving regioselectively to antilsyn-1,2-diols. The formation of the iso-regioisomer is suppressed using alpha-hydroxyacetone in DMSO at rt, achieving the corresponding anti-1,2-diol with ee's up to 85%. For alpha-alkoxyacetones (methoxy, benzyloxy, and tert-butyldimethylsilyloxy), the highest regio- and diastereoselectivity is achieved using alpha-methoxyacetone in DMF at 0 degrees C; the enantiomeric excess for the anti-1,2-isomer being up to 98%. (c) 2006 Elsevier Ltd. All rights reserved.