Proline–cyclodextrin conjugates: synthesis and evaluation as catalysts for aldol reaction in water
摘要:
The synthesis of six conjugates of L-proline and beta-cyclodextrin and their evaluation as catalysts of aldol reaction in water are described. The results indicated that the nature of the linker between proline and beta-cyclodextrin is important for catalytic activity: the one with the most flexible linker gave the best results. Inhibition experiments showed that the cavity of beta-cyclodextrin plays a role in the catalysis. Permethylation of the cyclodextrin hydroxyl groups led to higher conversion rates. (C) 2012 Elsevier Ltd. All rights reserved.
A direct de novo synthesis of ketoses and aminosugars by amino acid-catalyzed asymmetric aldol, Mannich and Michael reactions with dihydroxyacetone phosphate mimics as donors is presented. Proline, proline derivatives and thiazolidine-4-carboxylic acids catalyzed the asymmetric assembly of keto sugars and aminosugars in high yield with up to >99% ee. The organocatalytic C3+Cn methodology presented
提出了由氨基酸催化的不对称醛醇,曼尼希和迈克尔反应与二羟基丙酮磷酸酯模拟物作为供体的酮糖和氨基糖的直接从头合成。脯氨酸,脯氨酸衍生物和噻唑烷-4-羧酸以高达99%ee的高收率催化了酮糖和氨基糖的不对称组装。本文介绍的有机催化C 3 + C n方法是直接合成正交保护的C 4,C 5和C 6的从头合成酮糖,碳水化合物衍生物,氨基和氮杂糖以及聚草酰胺酸的总合成。添加水显着促进并改善了脯氨酸介导的仿生不对称CC键形成反应的对映选择性。
Dihydroxyacetone Variants in the Organocatalytic Construction of Carbohydrates: Mimicking Tagatose and Fuculose Aldolases
作者:Jeff T. Suri、Susumu Mitsumori、Klaus Albertshofer、Fujie Tanaka、Carlos F. Barbas
DOI:10.1021/jo0602017
日期:2006.5.1
Dihydroxyacetone variants have been explored as donors in organocatalytic aldol reactions with various aldehyde and ketone acceptors. The protected form of dihydroxyacetone that was chosen for in-depth study was 2,2-dimethyl-1,3-dioxan-5-one, 1. Among the catalysts surveyed here, proline proved to be superior in terms of yield and stereoselectivities in the construction of various carbohydrate scaffolds. In a fashion analogous to aldolase enzymes, the de novo preparation of L-ribulose, L-lyxose, D-ribose, D-tagatose, 1-amino-1-deoxy-D-lyxitol, and other carbohydrates was accomplished via the use of 1 and proline. In reactions using 2,2-dimethyl-1,3-dioxan-5-one 1 as a donor, (S)-proline can be used as a functional mimic of tagatose aldolase, whereas (R)-proline can be regarded as an organocatalytic mimic of fuculose aldolase.
Mimicking Dihydroxy Acetone Phosphate-Utilizing Aldolases through Organocatalysis: A Facile Route to Carbohydrates and Aminosugars
作者:Jeff T. Suri、Dhevalapally B. Ramachary、Carlos F. Barbas
DOI:10.1021/ol0502533
日期:2005.3.1
A practical and environmentally friendly organocatalytic strategy designed to mimic the DHAP aldolases has been developed and shown to be effective in the preparation of carbohydrates and aminosugars. (S)-Proline and (S)-2-pyrrolidine-tetrazole catalyzed the aldol reaction between dihydroxy acetone variants such as 1,3-dioxan-5-one and 2,2-dimethyl-1,3-dioxan-5-one with aldehydes to give the corresponding polyols in good yields with very high ees.
Mimicking Fructose and Rhamnulose Aldolases: Organocatalyticsyn-Aldol Reactions with Unprotected Dihydroxyacetone
作者:S. S. V. Ramasastry、Klaus Albertshofer、Naoto Utsumi、Fujie Tanaka、Carlos F. Barbas