Biodegradable Poly[(Amino Acid Ester)phosphazenes] for Biomedical Applications

Polyphosphazene derivatives with amino acid ester side groups were prepared by reacting poly(dichlorophosphazene) with ethyl esters of amino acids and were characterized by 1H, 31P-NMR and DSC analyses. The in vitro rate of degradation of these polymers depended on the nature of the amino acids while introducing small amounts of depsipeptide ester co-substituents increased degradation rates. The rate of hydrolytic degradation of the poly[(organo)phosphazene] materials could be controlled by the amino acid ester by the depsipeptide ester side group content and by blending poly[(amino acid ester)phosphazenes] with poly[(amino acid ester)-co-(depsipeptide ester)phosphazenes]. Poly[(glycine ethyl ester)phosphazenes] prepared from poly[(dichloro)phosphazenes] degradation rates were independent of molecular weight. Degradations of polymer blends indicate that an intramolecular catalysis ofthe polymer by the pendent carboxylic acid.

GABA(B)-agonistic activity of certain baclofen homologues

Baclofen (1) is a potent and selective agonist for bicuculline-insensitive GABA(B) receptors and is used clinically as an antispastic and muscle relaxant agent. In the search for new bioactive chemical entities that bind specifically to GABA(B) receptors, we report here the synthesis of certain baclofen homologues, namely (R,S)-5-amino-3-arylpentanoic acid hydrochlorides (R,S)-1a-h as well as (R,S)-5-amino-3-methylpentanoic acid [(RS)-1i] to be evaluated as GABA(B)R agonists. Compound 1a is an agonist to GABA(B) receptors with an EC₅₀ value of 46 μM on tsA201 cells transfected with GABA(B1b)/GABA(B2)/Gqz5, being the most active congener among all the synthesized compounds.

Phosphorous-containing analogues of aspartame

Four analogues of aspartame (aspartylphenylalanine methyl ester) were prepared in which one of the carboxylate groups was replaced by a phosphonate group. None of the peptides so obtained was sweet, in contrast with the parent compound which is over 100 times sweeter than sucrose. These results contrast with several published reports of phosphonate analogues of amino acids and peptides which are potent inhibitors of enzymes containing acceptor sites for the parent compound.

THE SELECTIVE DEGRADATION OF WHEAT GLUTEN

A method believed to hydrolyze peptide bonds of proteins selectively at the amino groups of serine was used to obtain polypeptides from wheat gluten. The procedure involved the use of strong acid and introduced appreciable amounts of sulphur into the products possibly as sulphonic acid groups. Most of the serine appeared at the amino termini of the peptides. The peptides displayed a striking electrophoretic homogeneity which may at least in part be accounted for by the acquired acid groups. Osmotic pressure measurements indicated an average molecular weight near 20,000 and terminal group estimates indicate that each molecule contained several N-terminal serine residues. There appeared to be strong association or chemical cross linking between peptide chains of the degraded gluten.