88820-87-5Relevant articles and documents
Quaternized α,α′-Amino Acids via Curtius Rearrangement of Substituted Malonate-Imidazolidinones
Gokada, Maheswara Rao,Hunter, Roger,Andrijevic, Ana,Petersen, Wade F.,Samanta, Sauvik,Venter, Gerhard,Rees-Jones, Sophie
, p. 10650 - 10658 (2018/05/31)
An efficient synthesis protocol is presented for accessing quaternized α-amino acids in chiral, nonracemic form via diastereoselective malonate alkylation followed by C- to N-transposition. The key stereodifferentiating step involves a diastereoselective alkylation of an α-monosubstituted malonate-imidazolidinone, which is followed first by a chemoselective malonate PMB ester removal and then a Curtius rearrangement to provide the transposition. The method demonstrates a high product ee (89-99% for eight cases) for quaternizing a range of proteinogenic α-amino acids. The stereogenicity in targets 5a-i supports previous conclusions that the diastereoselective alkylation step proceeds via an α-substituted malonate-imidazolidinone enolate in its Z-configuration, with the auxiliary in an s-transC-N conformation.
Enantioselective syntheses of aeruginosin 298-A and its analogues using a catalytic asymmetric phase-transfer reaction and epoxidation
Ohshima, Takashi,Gnanadesikan, Vijay,Shibuguchi, Tomoyuki,Fukuta, Yuhei,Nemoto, Tetsuhiro,Shibasaki, Masakatsu
, p. 11206 - 11207 (2007/10/03)
We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogues, in which all stereocenters were controlled by a catalytic asymmetric phase-transfer reaction and epoxidation. Furthermore, drastic counteranion effects in phase-transfer catalysis were observed for the first time, making it possible to three-dimensionally fine-tune the catalyst (ketal part, aromatic part, and counteranion). Copyright
Synthesis of enantiopure functionalized pipecolic acids via amino acid derived N-acyliminium ions
Rutjes, Floris P. J. T.,Veerman, Johan J. N.,Meester, Wim J. N.,Hiemstra, Henk,Schoemaker, Hans E.
, p. 1127 - 1135 (2007/10/03)
The synthesis and enzymatic resolution of a novel vinylsilane-containing amino acid is described. Derivatization of this and other olefinic amino acids followed by subjection to standard N-acyliminium ion cyclization conditions provides the corresponding pipecolic acid derivatives with - in most cases - complete conservation of enantiopurity. In addition to studying the scope of this reaction, details of the N-acyliminium ion cyclization including an aza Cope equilibrium are highlighted.
