Molybdenum Oxides as Highly Effective Dehydrative Cyclization Catalysts for the Synthesis of Oxazolines and Thiazolines
作者:Akira Sakakura、Rei Kondo、Kazuaki Ishihara
DOI:10.1021/ol050543j
日期:2005.5.1
In the presence of molybdenum oxide the dehydrative cyclization of N-acylserines, N-acylthreonines, and N-acylcysteines can be carried out under Dean-Stark conditions in toluene to give oxazolines and thiazolines. The ammonium salts (NH(4))(6)Mo(7)O(24).4H(2)O and (NH(4))(2)MoO(4) have excellent catalytic activities for the dehydrative cyclization of serine and threonine derivatives, and the acetylacetonate
available molybdenum(VI) oxides such as (NH4)2MoO4, (NH4)6Mo7O24·4H2O, MoO2(acac)2, and MoO2(TMHD)2 are highly effective dehydrative cyclization catalysts for the synthesis of a variety of oxazolines. The reaction proceeds with a complete retention of configuration at the β-position. For the dehydrative cyclization of cysteine derivatives, bis(2-ethyl-8-quinolinolato)dioxomolybdenum(VI) shows remarkable
(NH 4)2 MoO 4,(NH 4)6 Mo 7 O 24 ·4H 2 O,MoO 2(acac)2和MoO 2(TMHD)2等市售氧化钼(VI)是高效的脱水环化反应用于合成各种恶唑啉的催化剂。反应进行时将构型完全保留在β位。对于半胱氨酸衍生物的脱水环化反应,双(2-乙基-8-喹啉酮基)二氧钼(VI)显示出显着的催化活性,并在没有明显损失立体化学完整性的情况下提供了噻唑啉。C 2-外甲硫氨酸的位置。
Catalytic Synthesis of Peptide-Derived Thiazolines and Oxazolines using Bis(quinolinolato)dioxomolybdenum(VI) Complexes
I) (9) (1 mol %) shows remarkable catalytic activity for the dehydrative cyclization of cysteine-containing dipeptides 1 to give the corresponding thiazolines 2 with less than 6 % epimerization at the C2-exomethine position. For the dehydrative cyclization of threonine-containingdipeptides 4, 1 mol % of bis(2-phenyl-8-quinolinolato)dioxomolybdenum(VI) (10) gives the corresponding oxazolines 5 with
Total Synthesis of the Proposed Microcyclamides MZ602 and MZ568
作者:Yi Liu、Xiangyun Zhao、Hongbo Wang、Huili Liu、Zhuyin Sui、Bingfei Yan、Yuguo Du
DOI:10.1021/acs.joc.0c02541
日期:2021.1.1
of the proposed natural microcyclamide MZ602, except to an opposite sign of the optical rotation value. Surprisingly, the synthetic MZ568 (2) presented large discrepancies in characteristicspectral data from those of the reported natural product, although the absolute configuration of key intermediate 36 was unambiguously determined by single-crystal X-ray analysis in our work. These findings revealed
拟议结构的微环酰胺MZ602(1)和MZ568(2)的第一个收敛性全合成反应已通过11个线性步骤完成,总产率分别为12.5和16.8%。合成的关键特征包括一锅级联反应以构建核心Boc - 1 -Ile-Thz-OAllyl片段5,以及可移动的假脯氨酸(ΨMe ,Me pro)诱导剂辅助的含噻唑的all- 1线性肽环化。合成MZ602的光谱数据(1 H NMR,13 C NMR和HRMS)(1)与拟议的天然微环酰胺MZ602非常相似,除了旋光度值的符号相反。出人意料的是,尽管我们的工作通过单晶X射线分析明确确定了关键中间体36的绝对构型,但合成MZ568(2)在特征光谱数据上与报告的天然产物却存在较大差异。这些发现表明,天然微环酰胺MZ602和MZ568的拟议结构需要修改。