Stereospecific lithium-halogen exchange of alkenyl iodides was performed upon treatment with butyllithium in non-polar solvents such as hexane, benzene, and toluene at 25 °C to provide alkenyllithiums quantitatively with retention of the configuration. Metal-iodine exchange of allenyl iodides with n-BuLi, i-PrMgBr or Et2Zn was also performed effectively to afford the corresponding allenylmetallic reagents
An Improved Procedure for the Preparation of the<i>O</i>,2-Dianion of Allyl Alcohol
作者:Sayee G. Hegde、David C. Myles
DOI:10.1080/00397919708006818
日期:1997.6
Abstract An improved procedure for the preparation of the O,2-dianion of allylalcohol is described. The use of the magnesium alkoxide of 2-bromopropen-1-ol instead of the known lithium salt, suppresses dehydrohalogenation upon treatment with tert-butyl lithium and furnishes the dianion. Addition of this dianion to a variety of carbonyl compounds affords the expected products in good yield.
Asymmetric Synthesis of Functionalizable Type II β-Turn-Inducing α-Amino Acid Building Blocks
作者:Wenzheng Gao、Jiaxin Han、Sophie Greaves、Joseph P. A. Harrity
DOI:10.1021/acs.orglett.3c02376
日期:2023.9.8
α-amino acids, and in so doing, the side chain is sacrificed during the ring-forming process. We report a new asymmetric approach to lactam-constrained α-amino acid building blocks bearing a range of polar and hydrophobic side chains. The chemistry is amenable to rapidly generating di- and tripeptides, and the potential for these lactams to stabilize type II β-turns is demonstrated in the synthesis of the
肽模拟物正在成为一类有前途的有效和选择性疗法。在目前这些化合物的方法中,限制性内酰胺的利用是增强活性肽构象的关键因素,开发有效和立体控制的方法来生成此类内酰胺结构单元是一个重要目标。目前的方法通常依赖于现有 α-氨基酸的精制,这样做时,侧链在成环过程中被牺牲。我们报告了一种新的不对称方法,用于构建带有一系列极性和疏水侧链的内酰胺限制的 α-氨基酸结构单元。该化学物质适合快速生成二肽和三肽,并且这些内酰胺稳定 II 型 β 转角的潜力在黑素细胞抑制因子拟肽的合成中得到了证明。
Synthesis of Bridged Cycloisoxazoline Scaffolds via Rhodium-Catalyzed Coupling of Nitrones with Cyclic Carbonate
作者:Man Zhu、Mengdie Zhu、Fangjie Wei、Chongjing Shao、Xingwei Li、Bingxian Liu
DOI:10.1021/acs.joc.3c01840
日期:2023.12.1
Bridged isoxazolidines were synthesized via Rh(III)-catalyzed C–H allylation of α-aryl nitrones with 5-methylene-1,3-dioxan-2-one. The nitrone group serves as a directing group and 1,3-dipole in the C–H activation/[3 + 2] cycloaddition cascade, exhibiting excellent chemo- and stereoselectivity along with good functional group compatibility. The resulting skeletal structure was conveniently modified