77867-79-9Relevant academic research and scientific papers
2-Alkoxy-5(4H)-oxazolones from N-alkoxycarbonylamino acids and their implication in carbodiimide-mediated reactions in peptide synthesis
Benoiton, N. Leo,Chen, Francis M. F.
, p. 384 - 389 (2007/10/02)
Reaction of N-ethyl,N'-(γ-dimethylaminopropyl)-carbodiimide*HCl with one equiv. of N-tert-butoxycarbonyl-L-valine (3a) in dichloromethane at 23 degC gives, besides the symmetrical anhydride (5a), the optically pure 2-tert-butoxy-4-isopropyl-5(4H)-oxazolone (4a) which can be obtained in 50percent yield under selected conditions.The 2-benzyloxycarbonyl-4-isopropyl-5(4H)-oxazolone (4b) is similarly obtainable from N-benzyloxycarbonyl-L-valine (3b).Anhydrous acid converts 4a to the oxazolidinedione.Simple preparations of the N-carboxyanhydrides of valine and isoleucine have been devised from these reactions.Compound 4 reacts with 3 to give 5.Compound 4 reacts with an amino acid ester to give the optically pure peptide even in the presence of salts, but partial racemization occurs for reactions in the presence of a tertiary amine.Evidence for the implication of 2-alkoxy-5(4H)-oxazolones in the couplings of N-alkoxycarbonylamino acids is presented.Compound 4a has been isolated in 6-11percent yield from carbodiimide-mediated reactions of 3a with itself or amino acid methyl esters which have been terminated before completion.
Reaction of N-t-Butoxycarbonylamino Acid Anhydrides with Tertiary Amines and Carbodi-imides. New Precursors for 2-t-Butoxyoxazol-5(4H)-one and N-Acylureas
Benoiton, N. Leo,Chen, Francis M. F.
, p. 1225 - 1227 (2007/10/02)
N-t-Butoxycarbonylamino acid anhydrides react with tertiary amines to give 2-t-butoxyoxazol-5(4H)-ones, and with N,N'-dialkylcarbodi-imides to give the oxazol-5(4H)-ones and the N-acyl-N,N'-dialkylureas.
