Condensation of carboxylic acids 1 and 5 with unprotected α-amino acids 2 via activation by ethyl chloroformate and triethylamine proceeded effectively to afford the corresponding amides in 50–99% yields. Tripeptide 7c was obtained in 42% yield from the dipeptide 6c in a similar manner.
Convenient primary amidation of N-protected phenylglycine and dipeptides without racemization or epimerization
作者:Takuya Noguchi、Seunghee Jung、Nobuyuki Imai
DOI:10.1016/j.tetlet.2013.11.042
日期:2014.1
Primary amidation of N-protected phenylglycine and dipeptide proceeded easily to afford the corresponding amides in 57–95% yields with 99% ee and 81–99% de, respectively. The procedure is very easy to avoid racemization and epimerization of the products in the reactions by keeping exactly the reaction temperature at −15 °C when the activation of carboxylic acids, followed by the reaction of the mixed
Phenylalinine derivatives having the general formula:
and their non-toxic salts, have been found to promote the absorption of medicinal substances such as insulin. In the above formula, R' is a hydrogen atom, a fluorine atom, a nitro group, a hydroxyl group or a hydroxyl group protected by an esterifying group, X is -CO- or -SO2-, -Y- is a straight bond, a lower alkylene group, a substituted or unsubstituted vinylene group, or a group having the form- fula -CH2-O- or -0-CH2-, and R2 is a substituted or unsubstituted phenyl or naphthyl group; or the group R2-Y-CO- is an N-benzyloxy-carbonylphenylalanyl group, an N-benzyloxycarbonyl-4-flurophenylalanyl group or an N-(m-methoxycinnamoyl)phenylalanyl group.
Dipeptides and amides were obtained in high yields from N-carbobenzyloxy a-amino acids and 3-phenylpropanoic acid with unprotected a-amino acids via the corresponding mixed carbonic carboxylic anhydrides using ethyl chloroformate and triethylamine by an ecological and convenient method in which the protection of C-terminals is not needed. (C) 2016 Elsevier Ltd. All rights reserved.