Cob(I)阿拉明als Katalysator。6. Mitteilung [1]。Bildung and Fragmentierung von Alkylcobalaminen,ein Gleichgewichtsprozess zwischen nukleophiler Addition and reduktiver Fragmentierung
Tandem reduction–olefination of triethyl 2-acyl-2-fluoro-2-phosphonoacetates and a synthetic approach to Cbz-Gly-Ψ[(Z)-CFC]-Gly dipeptide isostere
摘要:
(Z)-alpha-Fluoro-alpha,beta-unsaturated esters (Z)-7a-f were stereoselectively prepared by a tandem reduction-olefination of triethyl 2-acyl-2-fluoro-2-phosphonoacetates 6a-f with NaBH4 in EtOH. A concise synthesis of Cbz-Gly-Psi[(Z)-CF=C]-Gly (26) as a dipeptide isostere was achieved via the tandem reduction-olefination of the corresponding 2-acyl-2-fluoro-2-phosphonoacetate 20. (c) 2006 Elsevier Ltd. All rights reserved.
Dehydroamino acid (Dhaa) is recognized as a useful tool or substrate for amino acid and peptide research. Although the stereoselective synthesis of the thermodynamically more stable Z-Dhaa has been well examined and established, the stereoselective synthesis of E-Dhaa has still remained to be a challenging synthetic task. In this paper, a stereoselective synthesis of E-Dhaa esters using a new (α-d
脱氢氨基酸 (Dhaa) 被认为是氨基酸和肽研究的有用工具或底物。尽管热力学上更稳定的 Z-Dhaa 的立体选择性合成已得到充分研究和确立,但 E-Dhaa 的立体选择性合成仍然是一项具有挑战性的合成任务。在本文中,描述了使用新的(α-二苯基膦酰基)甘氨酸立体选择性合成 E-Dhaa 酯。新方法的特征方面总结如下:(i)金属添加剂在促进 E 立体选择性方面起着重要作用。(ii) NaI 用于合成带有芳基取代基和氨基官能团的 E-Dhaas,
Chromatography-Free Wittig Reactions Using a Bifunctional Polymeric Reagent
作者:Peter Shu-Wai Leung、Yan Teng、Patrick H. Toy
DOI:10.1021/ol1021614
日期:2010.11.5
The first example of a polystyrene bearing two distinct reagent groups has been prepared. This phosphine and amine functionalized material was used in one-pot Wittig reactions with an aldehyde and either an α-halo-ester, -ketone, or -amide. Due to the heterogeneous nature of the polymer, the desired alkene product of these reactions could be isolated in excellent yield in essentially pure form after
Polyethyleneimine-Supported Triphenylphosphine and Its Use as a Highly Loaded Bifunctional Polymeric Reagent in Chromatography-Free One-Pot Wittig Reactions
作者:Patrick Toy、Xuanshu Xia
DOI:10.1055/s-0034-1380810
日期:——
rted triphenylphosphine reagent has been synthesized and used as a highly loaded bifunctional homogeneous reagent in a range of one-potWittigreactions that afforded high yields of the desired products after simple purification procedures. The approach also served efficiently in tandem reaction sequences involving a one-potWittigreaction followed by conjugate reduction of the newly formed alkene
Acyclic Stereoselection in the Ortho Ester Claisen Rearrangement
作者:G. William Daub、James P. Edwards、Carol R. Okada、Jana Westran Allen、Claudia Tata Maxey、Matthew S. Wells、Alexandra S. Goldstein、Michael J. Dibley、Clarence J. Wang、Daniel P. Ostercamp、Steven Chung、Paula Shanklin Cunningham、Martin A. Berliner
DOI:10.1021/jo9614250
日期:1997.4.1
The ortho ester Claisen rearrangement of trisubstituted allylicalcohols exhibits significant levels of diastereoselection. In E allylicalcohols, a 1,3-diaxial interaction develops in the chairlike transition state leading to the anti isomer, rendering the reaction syn selective by a factor of 3-5 to 1. In Zallylicalcohols, the 1,3-diaxial interaction develops in the transition state leading to
ethyl α-bromoacetate with aliphatic, aromatic, and heteroaromatic aldehydes in the presence of tri-n-butylphosphine and tetrabutylammonium fluoride produced α,β-unsaturated esters in good to excellent yields and E-stereoselectivity. Under the same conditions, reactions of ethyl α-bromopropionate, α-bromo acetonitrile, and α-bromoacetophenone with aliphatic and aromatic aldehydes in the presence of tri-n-butylphosphine
摘要 开发了一种一锅法、氟化物促进的 Wittig 反应。在三正丁基膦和四丁基氟化铵的存在下,α-溴乙酸乙酯与脂肪族、芳香族和杂芳香族醛的反应产生了 α,β-不饱和酯,收率和 E-立体选择性都非常好。在相同条件下,α-溴丙酸乙酯、α-溴乙腈和 α-溴苯乙酮与脂肪族和芳香族醛在三正丁基膦和四丁基氟化铵的存在下反应,在良好的 E 中产生了预期的 α,β-不饱和衍生物-立体选择性。该协议扩展到半稳定叶立德并应用于一些考布他汀类似物的合成。