丙酮酸体系在 25 o C 时的丙酮酸系统的酮-烯醇平衡常数通过迈耶卤素滴定法以及另一种方法来确定,该方法将这些常数作为烯醇化与酮化速率常数的比率,KE = k E /k K 。每种方法的测量均在酸性和碱性溶液中进行,酮化速率测量所需的烯醇通过甲硅烷基衍生物的水解以及平衡的 DMSO 溶液提供,其中烯醇含量大于在水中的含量
A novel Pd(II)-catalyzed cascade reaction has been developed that consists of a highly regio- and stereoselective oxa [4 + 2] cycloaddition reaction of o-alkynylbenzaldehydes and an intramolecular carboxylic group quenching of the in situ generated oxonium ion. This new reaction provides a one-step construction of the tetracyclic core structure of chaetophenol C from two simple starting materials.
A convenient synthesis of phosphoenolpyruvate via silyl-ester intermediate
作者:Mitsuo Sekine、Tetsuaki Futatsugi、Kohji Yamada、Tsujiaki Hata
DOI:10.1016/s0040-4039(01)85476-9
日期:1980.1
Kettenverlängerung von 1-desoxy-1-nitroalditolen durch nitriloxid-cycloaddition. Synthese von 4-N-substituierten 3,4-didesoxy-2-ulosonsäuren
作者:Hans Mack、Reinhard Brossmer
DOI:10.1016/s0040-4020(98)00168-9
日期:1998.4
Treatment of protected nitroalditols 1a or 2 with silylenolpyruvate (3) or methyl acrylate leads via nitrile oxide cycloadditon to cycle-tautomers of oximes, 5 or 4, respectively 4,5-dihydro-isoxazole 6. N-Acetyl-4-deoxy-4-(E/Z)-hydroxyimino-neuraminic acid (7) is obtained by deprotection of 4. Hydrogenation of 7 yields N-acetyl-4-amino-4-deoxy-neuraminic acid (9) and pentahydroxy-nononic acids 12a,b. The synthesis is useful for the chain extension of protected nitroalditols 13a and 20a, to give the corresponding oximes 15 and 22. This work provides a general method for the extension of sugar chains by three C-atoms and thus a novel synthesis of cr-keto acids containing an oxime and amino function. (C) 1998 Elsevier Science Ltd. All rights reserved.
Studies on the synthesis of tetronolide. Synthesis of a spiro-.alpha.-acyltetronic acid model