The asymmetric alkylation of Schiff bases under basic conditions in a ball mill was performed. The starting Schiff bases of glycine were prepared beforehand by milling protected glycine hydrochloride and benzophenone imine, in the absence of solvent. The Schiff base was then reacted with a halogenated derivative in a ball mill in the presence of KOH. By adding a chiral ammonium salt derived from cinchonidine
Identification of a highly effective asymmetric phase-transfer catalyst derived from α-methylnaphthylamine
作者:Barry Lygo、Bryan Allbutt、S.Russell James
DOI:10.1016/s0040-4039(03)01352-2
日期:2003.7
chiral amines with a series of conformationally dynamic biphenyl units. Screening of this library against the alkylation of a glycine imine has led to the identification of a highlyeffectiveasymmetric phase-transfer catalyst derived from α-methylnaphthylamine.
Flexible, Phase-Transfer Catalyzed Approaches to 4-Substituted Prolines
作者:Heather J. Johnston、Fergus S. McWhinnie、Felicetta Landi、Alison N. Hulme
DOI:10.1021/ol502239g
日期:2014.9.19
A range of 4-substituted prolines can be rapidly synthesized from a protected glycine Schiff base in only four steps and in 27-55% overall yield. Phase transfer catalysis allows direct access to both enantiomeric series, and the relative stereochemistry at the 4-position is readily controlled (>10:1 dr) through the choice of hydrogenation conditions.
Thiol Mediated Free Radical Cyclization of Alkenyl and Alkynyl Isocyanides
作者:Mario D. Bachi、Anna Balanov、Nira Bar-Ner
DOI:10.1021/jo00104a035
日期:1994.12
Thiol-mediated free radical cyclizations of but-3-enyl and but-3-ynyl isocyanides of types 6-8 give new access to 3,5-disubstituted 2-(alkyl- and 2-(arylthio)pyrrolines 11, 12, and 18. When 2-mercaptoethanol is used with the same isocyanides the reaction results in pyroglutamates 16, 17, or 19. These cyclizations involve the formation of a new carbon-carbon bond through intramolecular addition of a carbon-centered thioimidoyl radical to a carbon-carbon multiple bond. Although cyclic products are usually obtained in high yields, in a few cases a competing radical degradation process leading to isothiocyanates was observed. Isocyanide 8a carrying an allyl(phenyl) sulfide moiety isomerizes to 2-(phenylthio)pyrroline 24 in a series of sequential steps.
Total synthesis of (±)-manzacidin D
作者:Christian Drouin、Jacqueline C.S. Woo、D. Bruce MacKay、Roch M.A. Lavigne
DOI:10.1016/j.tetlet.2004.08.038
日期:2004.9
We report herein the first total synthesis of the alkaloid manzacidin D, in 11 steps and 16% overall yield from commercially available glycine tert-butyl ester hydrochloride. Our synthesis demonstrates for the first time in a total synthesis the utility of two different methodologies. A highly diastereoselective iodocyclization of an olefinic isothiourea is used to induce stereocontrol at the quaternary centre, and to form the heterocyclic core. Conversion of a thiourea to the requisite formamidine is achieved in good yield using our modified procedure. (C) 2004 Elsevier Ltd. All rights reserved.