The 4-hydroxy 4-substituted glutamicacid moiety is a common substructure of biologically important natural products such as monatin [(2S,4S)-2], lycoperdic acid (3), and dysiherbaine (4). To develop methodology for syntheses of these natural products, cycloadditions of nitrone 5 with 2-substituted 2-propen-1-ols 6 and 2-substituted acrylates 8 were investigated. Reactions of nitrone 5 with alcohols
The total synthesis of neodysiherbaine A was achieved via 1,3-dipolarcycloaddition of a chiral nitrone template with a sugar-derived allyl alcohol in the presence of MgBr2·OEt2. This cycloaddition constructed the C2 and C4 asymmetric centers in a single step. Then reductive cleavage, intramolecular SN2 reaction of the tertiary alcohol, and oxidation of the primary alcohol afforded neodysiherbaine
在MgBr 2 ·OEt 2存在的情况下,通过将手性硝酮模板与糖衍生的烯丙醇进行1,3-偶极环加成反应,可以实现新西西拜因A的总合成。这种环加成反应可一步完成C2和C4不对称中心的构建。然后进行还原裂解,叔醇的分子内S N 2反应和伯醇的氧化,得到了新地西尔巴因A。
[3+2] Route to Quaternary Oxaprolinol Derivatives as Masked Precursors of Disubstituted β<sup>3</sup>,β<sup>3</sup>-Amino Aldehyde
作者:Pavlo Shpak-Kraievskyi、Amelle Mankou Makaya、Anne Beauchard、Arnaud Martel、Mathieu Y. Laurent、Gilles Dujardin
DOI:10.1002/ejoc.201500339
日期:2015.6
introduced and was shown to afford chemoselectively a quaternary isoxazolidine derivative (of oxaprolinol-type) without cleaving the N–O isoxazolidine bond. Keeping the aldehyde function masked as a cyclic pseudo-acetal, the liberated oxy-amine function was shown to be available for a pseudo-peptide coupling with various N-protected amino acids. The isoxazolidine ring was opened by a reductive N–O bond cleavage
由带有苯基甘氨醇手性助剂的功能性环状酮硝酮开始形成显示一个或两个季立体中心的双环异恶唑烷。这些产品与一系列富电子和缺电子的偶极亲电子试剂进行立体控制的 1,3-偶极环加成反应。引入了一种新的苯基甘氨醇手性助剂的还原去除方法,并显示出化学选择性地提供了季异恶唑烷衍生物(恶丙醇型),而不会裂解 N-O 异恶唑烷键。将醛功能掩蔽为环状假缩醛,释放出的氧胺功能显示可用于与各种 N 保护氨基酸的假肽偶联。异恶唑烷环通过还原性 N-O 键断裂打开,
Approach to Monobactams and Nocardicins via Diastereoselective Kinugasa Reaction
A Kinugasa reaction between copper(I) acetylides and cyclic nitrones derived from chiral amino alcohols and glyoxylic acid is reported. The stereochemical preferences observed in this reaction are discussed. The alkyne molecule approaches the nitrone exclusively anti to the large substituent next to the nitrogen atom to provide the cis-substituted β-lactam ring preferentially. The six-membered oxazinone