Enantioselective synthesis of non-proteinogenic amino acids via metallated bis-lactim ethers of 2,5-diketopiperazines
作者:Ulrich Schöllkopf
DOI:10.1016/s0040-4020(01)91926-x
日期:1983.1
excess = asymmetric induction) of the adduct exceeds 95%. On hydrolysis the adducts are cleaved liberating the chiral auxiliary (used to build up the bis-lactim ether 1) and the target molecules, the opticallyactive amino acid methyl esters of type 8,19,25 or 36. The two amino acid esters are separable either by fractional distillation or (eventually after further hydrolysis to amino acids) by chromatography
Total Synthesis and Structure Elucidation of JBIR-39: A Linear Hexapeptide Possessing Piperazic Acid and γ-Hydroxypiperazic Acid Residues
作者:Masahito Yoshida、Naoki Sekioka、Miho Izumikawa、Ikuko Kozone、Motoki Takagi、Kazuo Shin-ya、Takayuki Doi
DOI:10.1002/chem.201406020
日期:2015.2.9
The totalsynthesis and stereochemical structural elucidation of JBIR‐39, containing four nonproteinogenic piperazic acid (Piz) residues, is reported. The synthesis includes Sc(OTf)3‐catalyzed acylation of a Piz(γ‐OTBS) derivative with piperazic acid chloride, providing the desired Piz‐Piz(γ‐OTBS) dipeptide in high yield without epimerization. After assembling two additional Piz moieties and (S)‐isoleucic
Synthesis of α,α-Disubstituted α-Amino Acid Derivatives in Enantiopure Form via Stereoselective Addition of Grignard Reagents to a Chiral Acyclic Nitrone Derived from L-Erythrulose
作者:Raul Portolés、Juan Murga、Eva Falomir、Miguel Carda、Santiago Uriel、J. Alberto Marco
DOI:10.1055/s-2002-25358
日期:——
The additions of various Grignard reagents to a chiral nitrone prepared from L-erythrulose take place with variable diastereoselectivity. The degree and strength of the facial selectivity can be modified if the reaction is performed in the presence of Lewis acidic additives: zinc bromide enhances attack to the si face whereas diethyl aluminum chloride promotes attack to the re side. The obtained adducts
Stereoselective addition of organometallic reagents to a chiral acyclic nitrone derived from l-erythrulose
作者:Juan Murga、Raul Portolés、Eva Falomir、Miguel Carda、J. Alberto Marco
DOI:10.1016/j.tetasy.2005.03.013
日期:2005.5
The additions of various organolithium and organomagnesium reagents to a chiralnitrone prepared from l-erythrulose took place with variable diastereoselectivity. The degree and strength of the facial selectivity can be modified if the reaction is performed in the presence of Lewis acid additives: zinc bromide enhances the attack to the Si face of the CN bond whereas diethyl aluminium chloride promotes