New amino-protecting groups with special application in peptide synthesis

Abstract

The introduction of a tertiary amino substituent into urethane-type protecting groups [as in ( l ) , (4), (8) and (12)] increases their acid-stability and provides a 'handle' for the facilitation of peptide synthesis ; analogues of t-butoxycarbonyl and benzyloxycarbonyl groups having NN-dimethylcarbamoyl substituents [(15) and (IS)], designed to increase the solubility of protected peptides in dimethylformamide, are also reported.

Hydroxy‐ and Amino‐protection Based on the 4‐dimethylcarbamoylbenzyl Group

“…providing a powerful electrophilic para substituent which will greatly hinder the approach of a second proton to the ether oxygen. This effect is similar to that noted by us when in acid-labile protecting groups phenyl residues are replaced by pyridyl, and other examples have been given by Coyle et al (1975Coyle et al ( , 1979, who have also described preliminary work on 2-dimethyl-HY DROXY-AND AMINO-PROTECTION carbamoylbenzyloxycarbonyl and 2-dimethylcarbamoylethylisopropoxycarbonyl derivatives o f amino-acids. 4-Dirnethylcarbamoylbenzyl bromide was prepared by the action of dimethylamine on a-bromo4-toluoyl bromide (Davies & Perkin, 1922) and it reacted with the copper complex of tyrosine giving compound 1 .…”

Heterocycles in organic synthesis. 11. Reactions of heteroaromatic N-oxides with pyridine and diazoles

“…13 Removal should also be easy. 14 As expected, the IV-oxide 25 readily reacted with triethylamine to give 26 (Scheme IV). With pyridine, 25 gave 27,1 -methylbenzimidazole similarly formed 30, and isoquinoline formed the corresponding quaternary salt, whereas benzimidazole itself, although yielding some of the monoadduct 29, mainly underwent a double reaction to yield 28.…”