synthesis of N‐carbamoyl‐L‐aminoacids is reported. The procedure, involving the reaction between urea and α‐aminoacids sodium salts, was performed under microwave conditions using an unmodified domestic microwave oven. A careful study of the operative conditions indicated proline (1d) as the less reactive substrate and phenylglycine (1e) as the more reactive one among all the α‐aminoacids tested. Substitution
Quantitative N-deprotection without racemisation was then achieved in the solid through nitrosation by gaseous NOx. The extent of racemisation occurring in the coupling step is discussed. In the second application, an easy route to amino acid N-carboxy anhydrides (NCAs) through nitrosation of CAA under the same conditions as above allowed straightforward “one-pot” peptide stepwise coupling, as demonstrated
Investigation of<i>N</i>-carbamoylamino acid nitrosation by {NO + O<sub>2</sub>} in the solid-gas phase. Effects of NO<i>x</i>speciation and kinetic evidence for a multiple-stage process
Nitrosation of N-carbamoylamino acids (CAA) by gaseous NO + O2, an interesting synthetic pathway to amino acid N-carboxyanhydrides (NCA), alternative to the phosgene route, was investigated on N-carbamoyl-valine either in acetonitrile suspension or solventless conditions, and compared to the classical nitrosating system NaNO2 + CF3COOH (TFA), the latter being quite less efficient in terms of either
用气态NO + O 2将N-氨基甲酰基氨基酸(CAA)亚硝化,这是一种有趣的合成方法,可替代光气途径,生成氨基酸N-羧基酸酐(NCA),无论是在乙腈悬浮液中还是在无溶剂的N-氨基甲酰基缬氨酸上与传统的亚硝化系统NaNO 2 + CF 3 COOH(TFA)相比,后者在速率,化学计量需求或产品的进一步可加工性方面都效率较低。NO + O 2反应的速率和效率主要取决于O 2 / NO比。评价各种亚硝化物质(N 2通过化学计量平衡的O 3,N 2 O 4,HNO 2)显示,该反应主要由N 2 O 3(对于低于0.3的O 2 / NO比率)和N 2 O 4(对于高于0.4的O 2 / NO比率)进行。(随后形成的)HNO 2的相对贡献始终保持很小。通过HNO 2(来自NaNO 2 + TFA),气态N 2 O 4或气态N 2 O 3的固相反应的差示扫描量热法(DSC)监控提供了相关的速率常数(分别在25°C时约为0
Microwave-Assisted Synthesis of N-Monosubstituted Urea Derivatives
作者:Lidia De Luca、Andrea Porcheddu、Giampaolo Giacomelli、Irene Murgia
DOI:10.1055/s-0030-1258553
日期:2010.10
An easy and rapid procedure for the preparation of N-monosubstituted ureas via reaction between potassium cyanate and a wide range of amines is described. The procedure was performed undermicrowaveirradiation using water as solvent. This methodology is particularly attractive since it provides ureas in high yield and purity.
Synthesis of 1S,5R- and 1R,5S-glycoluriles by diastereospecific α-ureidoalkylation of (S)/(R)-N-carbamoyl-α-amino acids with 4,5-dihydroxyimidazolidin-2-one
作者:Il’ya E. Chikunov、Angelina N. Kravchenko、Pavel A. Belyakov、Konstantin A. Lyssenko、Vladimir V. Baranov、Oleg V. Lebedev、Nina N. Makhova
DOI:10.1070/mc2004v014n06abeh002050
日期:2004.1
A diastereospecific method for the synthesis of individual enantiomers of 1S,5R- and 1R,5S-glycoluriles has been developed based on the α-ureidoalkylation of (S)/(R)-N-carbamoyl-α-amino acids with 4,5-dihydroxyimidazolidin-2-one.