Related Experiment Video
Updated: Jun 25, 2026

Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine
Published on: June 13, 2022
N-(ureidoethyl)amides of cyclic enkephalin analogs
Małgorzata Ciszewska1, Maria Kwasiborska, Michał Nowakowski
1Department of Chemistry, Warsaw University, Warsaw, Poland.
Abstract:
Novel N-(ureidoethyl)amides of cyclic enkephalin analogs have been synthesized. The p-nitrophenyl carbamate of 1-Boc-1,2-diaminoethane was coupled with 4-methylbenzhydrylamine (MBHA) resin. The Boc group was removed by treatment with HCl/dioxane, and the peptide chain was assembled using Boc strategy. For deprotection of amino function, HCl/dioxane was used. D-Lys or D-Orn were incorporated in position 2, and the side chains of Lys, Orn, Dab, or Dap in position 5 were protected with Fmoc group. Side chain protection was removed by treatment with 55% piperidine in DMF, and cyclization was achieved by treatment with bis-(4-nitrophenyl)carbonate to form a urea bridge. The peptide was cleaved from the resin by treatment with 45% TFA in DCM. The peptides were tested in the guinea-pig ileum (GPI) and mouse vas deferens (MVD) assays. Divers opioid activities were observed, depending on the size of the ring. In comparison with [Leu(5)]enkephalin, all peptides were more active in the GPI assay (between 125 and 12 times), and some of them were also more potent in the MVD assay. The conformational propensities of each peptide were determined using the EDMC method in conjunction with NMR experiments. This approach allows treating the dynamical behavior of small peptides properly. The results were compared with those obtained previously for corresponding nonsubstituted amides and are in agreement with the biologically active conformation proposed by us earlier.
Related Concept Videos
Aldehydes and Ketones with Amines: Enamine Formation Mechanism
Aldehydes and Ketones with Amines: Imine and Enamine Formation Overview
Types of Enols and Enolates
Preparation of Amides
The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
Subsequently, the amine acts as a nucleophile that attacks the acylating agent to form a tetrahedral intermediate. In the...
Adrenergic Agonists: Chemistry and Structure-Activity Relationship
Aromatic ring substitutions: Substituting the aromatic ring with –OH groups at positions 3 and 4 yields catecholamines (e.g., epinephrine), which have a high affinity for adrenoceptors. Hydrogen bonding between –OH groups and receptors enhances adrenergic activity.
Separation of the aromatic...
Nomenclature of Primary Amines

