Stereoselective Synthesis of Protected Ketohexoses via Aldol Reaction of Chiral Dioxanone Enolate
作者:Marek Majewski、Pawel Nowak
DOI:10.1055/s-1999-2862
日期:1999.9
Lithium and boron enolates of 2,2-dialkyl-1,3-dioxa-5-ones react with aldehydes to give aldol products in high diastereoselectivity and, when chiral lithium enolates are generated using optically pure chiral lithium amide bases, in high enantioselectivity. Dioxanone lithium enolates react readily with protected glyceraldehyde affording protected ketohexoses in high diastereo- and enantiomeric purity.
Prolinamido-glycosides, water-compatible organocatalysts, are capable of catalyzing the stereoselective aldolreaction in aqueous media. The aldolreaction of 2,2-dimethyl-1,3-dioxan-5-one with aldehydo sugars in the isopropylidene form gave ketoses stereoselectively. The stereochemistry of these aldolreactions has been investigated in terms of the influence of conformational effects, and the results demonstrate
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.
Aldol Addition of Lithium and Boron Enolates of 1,3-Dioxan-5-ones to Aldehydes. A New Entry into Monosaccharide Derivatives
作者:Marek Majewski、Pawel Nowak
DOI:10.1021/jo0002238
日期:2000.8.1
of stereoselectivity in aldolreactions of enolates derived from 1,3-dioxan-5-ones (4) are described. Boron enolates, generated in situ, react with benzaldehyde to give the corresponding anti aldol selectively (the anti:syn ratio of up to 96:4) and in high yield. Lithium enolates give high anti selectivity only with aldehydes branched at the alpha-position. Enantioselective deprotonation of C(S) symmetrical
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。