Mohmed K. Anwer

Structure-activity relationships of enkephalins containing serially replaced thiomethylene amide bond surrogates

An isomeric series of four leucine-enkephalin analogs containing the thiomethylene ether unit as an amide bond replacement in all positions have been prepared by solid phase methods. The resulting pseudopeptides divulged widely differing retentive behaviors on reversed phase high performance liquid chromatography (HPLC). An analog containing the Phe psi[CH2S]Leu dipeptide replacement at the 4-5 position exhibited binding close to the parent, leucine enkephalin; its guinea pig ileum (GPI) activity was the highest of the analogs tested. Another compound, Tyr psi[CH2S]Gly1-2]-Leu-enkephalin, also displaced 3H-etorphine well in the binding assay, but caused increased contractions in the GPI assay at low concentrations. The Phe psi[CH2S]Leu results are not compatible with the necessity of a beta-turn structure for agonist activity in the GPI assay.

Applications of ammonium formate catalytic transfer hydrogenolysis--IV1: a facile method for dehalogenation of aromatic chlorocarbons

Abstract Ammonium formate catalytic transfer hydrogenolysis, in the presence of palladium on carbon, has shown utility for the rapid dehalogenation of mono-or polychlorinated aromatic compounds in neutral media under ambient conditions of temperature and pressure.

A rapid non-acidolytic method for deprotection and removal of peptides from solid phase resins - applications of ammonium formate catalytic transfer hydrogenation

Abstract Ammonium formate aided catalytic transfer hydrogenation has been employed in the cleavage, and concommitant deprotection, of the pentapeptide leucine enkephalin from the Merrifield peptide resin under ambient conditions of temperature and pressure in a neutral medium.

Cleavage of esters using carbonates and bicarbonates of alkali metals: synthesis of thymopentin

Abstract A novel method for hydrolysis of primary esters using aqueous alkali carbonates or bicarbonates and an alcohol as cosolvent is described. Several peptide esters, including a Cbz-Arg-Lys(Cbz)-Asp(OBzl)-Val-Tyr-OBzl (sequence corresponding to the active site of thymic immunoregulatory hormone, thymopoietin), were hydrolyzed to demonstrate the utility of this method.

Cleavage of peptides bound to merrifield resins by potassium carbonate in the presence of a phase transfer reagent

Abstract Tetra-n-butylammonium carbonate (TBAC) [prepared in situ from potassium carbonate and tetra-n-butylammonium hydrogen sulphate (TBAHS) has been utilized to release peptides in an N α -protected form from their Merrifield resin supports. The partially protected peptides were obtained in good yields (70 to 100%) and purity (85 to 90% by reversed phase high performance liquid chromatography (RP-HPLC)).