Intramolecular cyclopropanation: stereospecific synthesis of (E)- and (Z)-1-aminocyclopropane-1-carboxylic acids
摘要:
tert-Butyl-substituted allyl malonates, prepared in two steps from malonic acid, are diazotized in high yields. The diazomalonates 7 undergo a stereospecific copper(I)-catalyzed cyclopropanation to give 1-(tert-butoxycarbonyl)-3-oxa-2-oxobicyclo[3.1.0]hexanes 8 which can be converted to the protected (E)- or (Z)-1-aminocyclopropane-1-carboxylic acids 10 or 15 via Curtius- or Hoffmann-type rearrangements, respectively. The sequences are short (six steps from malonic acid) and proceed with good overall yields (20-40% overall from malonic acid) The free amino acids 12 and 18 can be liberated in two steps.
Intramolecular cyclopropanation: stereospecific synthesis of (E)- and (Z)-1-aminocyclopropane-1-carboxylic acids
摘要:
tert-Butyl-substituted allyl malonates, prepared in two steps from malonic acid, are diazotized in high yields. The diazomalonates 7 undergo a stereospecific copper(I)-catalyzed cyclopropanation to give 1-(tert-butoxycarbonyl)-3-oxa-2-oxobicyclo[3.1.0]hexanes 8 which can be converted to the protected (E)- or (Z)-1-aminocyclopropane-1-carboxylic acids 10 or 15 via Curtius- or Hoffmann-type rearrangements, respectively. The sequences are short (six steps from malonic acid) and proceed with good overall yields (20-40% overall from malonic acid) The free amino acids 12 and 18 can be liberated in two steps.
Diazo transfer reactions under mildly basic conditions
作者:Ari M. P. Koskinen、Luis Muñoz
DOI:10.1039/c39900000652
日期:——
Practically quantitative diazotransfer from toluene-p-sulphonyl azide to active methylene compounds has been achieved rapidly undermildlybasicconditions with potassium carbonate in acetonitrile.
cyclopropanation of allyl diazomalonates and the corresponding phenyliodonium ylides was investigated with a series of chiral, non-racemic ligands. The reaction of 6b in the presence of the bis[dihydrooxazole] ligand Xa in refluxing 1,2-dichloroethane proceeded to 8b with an enantiomer excess (ee) of up to 72% under optimized conditions. In contrast, 8b resulting from reaction of ylide 7b with the same
用一系列手性非外消旋配体研究了铜催化的重氮丙二酸烯丙酯分子内环丙烷化反应和相应的苯基碘叶立德的对映选择性。6b 在双[二氢恶唑] 配体 Xa 存在下在回流的 1,2-二氯乙烷中的反应进行到 8b,在优化条件下对映异构体过量 (ee) 高达 72%。相比之下,由叶立德 7b 与相同配体反应产生的 8b,但在 0°的 CH2Cl2 中,ee 仅为 30%。然而,与其他配体相比,重氮丙二酸酯 6b 的对映选择性低于内立德 7b。乙酰乙酸衍生的苯基碘鎓叶立德 15b 的分子内环丙烷化得到具有 68% ee 和配体 Xa 的 16b,但相应的重氮化合物在暴露于手性铜催化剂时不反应。叶立德 7 和 15 的 Cu 催化反应中不对称诱导的观察与类卡宾机制一致;然而,在重氮丙二酸 6b 和叶立德 7b 之间观察到的对映选择性的差异表明,在铜的配位范围之外,环丙烷化的竞争性非选择性途径。
1-Amino-2-oxo-3-oxabicyclo[3.1.0]hexane (2,3-methanohomoserine lactone), a conformationally constrained amino acid
作者:Ari M. P. Koskinen、Luis Muñoz
DOI:10.1039/c39900001373
日期:——
A rapid high yielding synthesis of N-t-butoxycarbonyl-1-amino-2-oxo-3-oxabicyclo[3.1.0]hexane is described; the synthesis relies on an intramolecular carbenoid reaction of an appropriate malonate derivative followed by Curtius degradation to give the unprotected amino group.