Bridged (β-alkoxyalkyl)CoIII(salen) complexes by intramolecular alkoxycobaltation of unactivated alkenes: new models for coenzyme B12
作者:Rolf Blaauw、Irene E. Kingma、Jan H. Laan、Juul L. van der Baan、Sijbe Balt、Martinus W. G. de Bolster、Gerhard W. Klumpp、Wilberth J. J. Smeets、Anthony L. Spek
DOI:10.1039/b000196l
日期:——
but-2-en-1-yl (6c), but-3-en-1-yl (6d)] react with oxygen and alcohols to give organocobalt(III) complexes containing a β-alkoxy-substituted three- or four-carbon bridge between cobalt and the equatorial ligand. NMR and UV–VIS spectroscopic studies show that product formation is a three-stage process involving (1) oxidation of cobalt(II) to produce an (alkoxo)cobalt(III) complex, (2) intramolecular interaction
[EN] PROCESS FOR THE PREPARATION OF AN alpha-AMINO CARBONYL COMPOUND<br/>[FR] PROCEDE DE PREPARATION D'UN COMPOSE DOLLAR G(A)-AMINO CARBONYLE
申请人:DSM IP ASSETS BV
公开号:WO2004078702A1
公开(公告)日:2004-09-16
The invention relates to a process for the preparation of an α-amino carbonyl compound by reacting an imine starting material with a suitable electrophile in the presence of a base. This process has the advantage that the imine starting materials can be prepared from glyoxylic acid esters or glyoxylic acid ester derivatives and α-hydrogen containing primary amines, which are usually cheap and readily available. These imine starting materials can usually be prepared with a high yield and/or almost without the formation of any side products.
Synthesis of (optically active) sulfur-containing trifunctional amino acids by radical addition to (optically active) unsaturated amino acids
作者:Quirinus B. Broxterman、Bernard Kaptein、Johan Kamphuis、Hans E. Schoemaker
DOI:10.1021/jo00049a041
日期:1992.11
Sulfur-based radicals, generated from R-S-H-type precursors (R = alkyl, acyl) with AIBN, smoothly add to alpha-allylglycines protected at none, one, or both of the amino acid functions (NH2 and/or CO2H). Sulfur-containing trifunctional amino acids were obtained in good to excellent yields (64-100%). The solvent used for the reaction is critical. Optimal results were obtained when both the unsaturated amino acid and RSH dissolve completely in the medium (dioxane/water or methanol/water are good solvent systems). The scope of the reaction includes alpha-substituted alpha-allylglycine and derivatives as well as beta-substituted beta-allyl-beta-ammo alcohols. In the case of optically active alpha-allylglycine derivatives, radical addition is accompanied by a small amount of racemization, the amount depending on the type of protection and R-S-H. The products are easily optically enriched by crystallization. Addition of sulfur-based radicals to alpha-allylglycine is believed to be an example of a general method for synthesizing optically active trifunctional amino acids from unsaturated amino acids.
Synthesis of racemic .alpha.-amino carboxamides via Lewis acid-mediated reactions of .alpha.-methoxyglycinamide derivatives with allylsilanes: enzymic resolution to optically active .alpha.-amino acids
作者:Eric C. Roos、Hendrik H. Mooiweer、Henk Hiemstra、W. Nico Speckamp、Bernard Kaptein、Wilhelmus H. J. Boesten、Johan Kamphuis
DOI:10.1021/jo00051a019
日期:1992.12
A short and expedient synthetic route to optically active, saturated and gamma,delta-unsaturated alpha-amino acids is reported. The key step is a BF3.OEt2-mediated reaction of allylsilanes with N-(alkoxycarbonyl)-alpha-methoxyglycinamides 11-15, leading to the corresponding gamma,delta-unsaturated alpha-aminocarboxamides. The genuine S(N)1-character of this process with iminium ion 6 as intermediate is proven in the case of the glycine ester 10. Thus, reaction of enzymatically resolved 10 with pi-nucleophiles leads to racemic products. The most useful iminium precursors are the N-methoxyamides 12-14 providing good yields of coupling products. The most convenient N-protective group is the allyloxycarbonyl group. Deprotection proceeds via a Pd(0)-catalyzed transprotection to the corresponding BOC-protected analogues. Four examples of the enzymatic resolution of alpha-amino carboxamides, by using an L-specific aminopeptidase from Pseudomonas putida, are described in detail. Most notably, secondary N-methoxyamides are good substrates for the enzyme to provide the desired a-amino acids in high optical purity.
BRADBURY, ROBERT H.;ORIFFITHE, DAVID;RIVETT, JANET E., HETEROCYCLES, 31,(1990) N, C. 1647-1653
作者:BRADBURY, ROBERT H.、ORIFFITHE, DAVID、RIVETT, JANET E.