Rapid and Efficient Microwave‐Assisted Synthesis ofN‐Carbamoyl‐L‐amino Acids

A Practical Method for Amino Acid Analysis by LC-MS Using Precolumn Derivatization with Urea

“…These two AAs represent the characteristics of most AAs in the analysis, which can evaluate the effectiveness of the derivatization method well. Stock solutions of urea and Ala (or Phe) were mixed 1:1 and incubated at 60 °C [ 27 , 28 ]. This original condition was initially used to confirm whether the target product CAA could be generated.…”

“…Here, we present a method for derivatizing AAs with urea, based on LC-MS detection. Inspired by previous studies [ 27 ], we optimized the experimental conditions for the reaction between urea and AAs to generate carbamoyl amino acids (CAAs) in an aqueous solution without any pretreatment. The resulting CAAs from both standard AAs and complex samples show better performance in chromatographic separation and quantitative determination.…”

Efficient syntheses of 13C‐ and 14C‐labelled 5‐benzyl and 5‐indolylmethyl L‐hydantoins

“…The precipitate was collected by filtration to give N ‐carbamoyl‐ L ‐phenylalanine (634 mg, 3.05 mmol, 50%) as colourless crystals [Mp 192°C (lit. 188–190°C 21 , 193°C22). 1 H NMR (300 MHz, DMSO‐ d 6 ): δ = 11.45 (s, 1 H, OH), 7.31–7.17 (m, 5 H, Ar–H), 6.16 (d, 1 H, J = 8.3 Hz, NH), 5.63 (s, 2 H, NH 2 ), 4.32 (m, 1 H, J = 5.2 Hz and 10.8 Hz, CHCO), 2.92 (m, 2 H, J = 5.2 Hz, 7.8 Hz, and 13.9 Hz, CH 2 ).…”

Urea: A Useful and Inexpensive Chemical for Organic Synthesis

“…(A) N-Carbamoyl-L-amino acids are important synthetic intermediates for the synthesis of peptides and heterocycles. A microwaveassisted green synthesis of these compounds was described by Verardo et al 1 The reaction between urea and amino acid sodium salts in water followed by acidification furnished the desired compounds in good yields and optical purity. (B) Li et al 2 described the high-yielding synthesis of cyclic carbonates using the reaction of urea and diols catalyzed by metal oxides.…”

“…Urea was the first organic compound to be synthesized from inorganic reagents. This easily accessible chemical has been used as building block in the synthesis of N-carbamoyl-L-amino acids, 1 cyclic carbonates, 2 and many nitrogen-containing heterocycles such as pyridines, 3 pyrimidines, 4 3,4-dihydropyrimidinones, 5 oxazines, 6 1,3-ox-azin-3-ones, 7 and iminosugars. 8 Another application of urea in carbohydrate chemistry was described earlier.…”