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[alpha]-Amino acids and [alpha]-amino methyl esters are easily converted to their N-monoalkyl derivatives by a reductive condensation reaction using several carbonyl compounds in the presence of sodium borohydride. This reducing agent has shown a wide versatility with minor but essential procedural variations. The reaction allows the [alpha]-monodeuterium labeling of the new N-substituent by use of sodium borodeuteride. Key words: [alpha]-amino acid, [alpha]-amino methyl esters, sodium borohydride, reductive N-monoalkylation, carbonyl compounds.

The reaction of formaldehyde with enantiomerically pure α-N-protected amino acid hydrazides is described. The system has been investigated in different solvents, including both aqueous formaldehyde and paraformaldehyde, with the aim of simplifying the final reaction mixture. Aqueous formaldehyde in refluxing THF proved to be the best combination, affording mainly the corresponding monomeric N-methylene and 1,3,5-trisubstituted-1,3,5-hexahydrotriazine derivatives. The monomeric form was the only one present at high temperature, as evidenced by 1H and 13C NMR spectroscopy. [ABSTRACT FROM AUTHOR]

A rapid and efficient method for the synthesis of N-carbamoyl-L-amino acids is reported. The procedure, involving the reaction between urea and α-amino acids 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-amino acids tested. Substitution of urea with potassium cyanate produced a low conversion into the corresponding N-carbamoyl derivative, and a possible explanation of this result is reported. [ABSTRACT FROM AUTHOR]