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Biomedical subjects

C H Stammer

Publications and source records attributed to C H Stammer.

At least 37 records · Page 2Linked to original sources
PubMed1983

Dehydro-enkephalins. VIII. Attempted synthesis of dehydrotyrosine-enkephalins.

Two kinds of dehydropeptide analogs of enkephalin containing a delta Tyr unit at the N-terminus have been synthesized by coupling Boc-delta Tyr-(Cl2 Bzl)-OH with amino acid amides and tetrapeptide esters using the water soluble carbodiimide-HOBt method. Pentapeptides consisting of delta Tyr1, and delta Phe4 or delta Leu5 were also prepared. Ultraviolet difference spectroscopy was important in the characterization of the dehydro moieties, delta Tyr, delta Phe and delta Leu. Attempts to liberate delta Tyr1-enkephalins have been unsuccessful because of the instability of an N-terminal delta Tyr residue having p-phenolic group in the side chain.

Enkephalins↗
PubMed1982

Dehydro-enkephalins. III. Synthesis and biological activity of [delta Ala2, Leu5]-enkephalin.

[delta Ala2, Leu5]-enkephalin has been prepared and shown to be more active than the parent saturated enkephalin in a binding assay using rat brain membranes and [3H]dihydromorphine as a tracer. In a comparison of potencies against [3H]dihydromorphine and [3H]-[D-Ala2, D-Leu5]-enkephalin as tracers, [delta Ala2, Leu5]-enkephalin showed preference for micro opiate receptors, possibly due to the hydrophobicity of the delta Ala2 residue. A synthetic tetrapeptide enkephalin [delta Ala2]-desLeu5-enkephalin had weak activity and high selectivity for the micro receptors. O-Acylation of a serine residue in the peptide was achieved by coupling between the peptide and a carboxylic acid using DCC and a catalytic amount of 4-dimethylaminopyridine.

Animals↗
PubMed1982

Dehydro-enkephalins. VI. Dehydroalanine3-enkephalin: a potent enkephalin analog for the delta opiate receptor.

The Gly3 residue in Gly2- and D-Ala2-enkephalins has been replaced by delta Ala3 and Ser3 in order to examine the effect on binding to the delta and mu opiate receptors. [D-Ala2, delta Ala3, Leu5]-enkephalin maintains most of its receptor binding affinities for both sites. It is suggested that the proper conjunctions of positions 2 and 3 of the enkephalin sequence are important to receptor preference and that position 3 may have a very specific interaction with the delta receptor. The in vivo analgesic and CNS activities of the peptides are also discussed.

Analgesia↗
PubMed1978

5-Carboxamido-4-amino-3-isoxazolidone, and asparagine analogue.

trans-Aziridine-2,3-dicarboxylic ester was used to prepare the required beta-chlorohydroxamic acid used in the synthesis of the title compound. The trans configuration of the asparagine analogue was established by hydrogenolysis to erythro-beta-hydroxyasparagine amide. Neither the title compound nor the intermediate aziridinehydroxamic acid (8) showed significant activity against the L1210 and P-388 tumors. The title compound was inactive as an inhibitor of asparagine synthetase from Novikoff hepatoma and did not inhibit the growth of some 25 bacteria and fungi.

Animals↗
PubMed1978

The synthesis of N-benzyloxycarbonl-L-prolyl-dehydrophenylalanyl-L-histidyl-L-leucine: a converting-enzyme inhibitor.

The direct oxidation of a dipeptide azlactone (1) by DDG affords an optically active unsaturated dipeptide azlactone (2). It was shown that the double bond had the Z-configuration and that no racemization of the proline moiety occurred during the oxidation. The dehydrotripeptide, Z-Pro-delta-Phe-Phe OH (9b) was prepared by direct coupling of azlactone (2) with phenylalanine tetramethyl-guanidinium salt and was shown to be stable to chymotrypsin. The tetrapeptide, Z-Pro-delta-Phe-His-Leu OH (11), was prepared directly from the azlactone (2) and by saponification of the tetrapeptide ester (10) prepared by mixed anhydride coupling of Z-Pro-deltaPhe OH (7) with the dipeptide ester. The dehydropeptide (11) inhibits angiotensin I converting enzyme (IC50, 1X10-4 M).

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1977

3-hydroxyisoxazole-5-hydroxamic acid.

The synthesis of the title compound, 3-hydroxyisoxazole-5-hydroxamic acid (4b), by two procedures is described. The first, involving the treatment of dimethyl acetylenedicarboxylate with hydroxylamine, had previously been reported to give the 3-hydroxyisoxazole-5-carboxylic acid (4a). In the second, treatment of chlorofumaroyl dichloride with hydroxylamine also gave the intermediate chlorofumarodihydroxamic acid (6). Compound 6 was found to have some activity against P388 lymphocytic leukemia.

Animals↗
PubMed1976

Synthesis of N-hydroxythiourea.

The synthesis of the title compound (1) was accomplished by the conversion of 2,4-dimethoxybenzylamine (2) into an isothiocyanate (3) using thiocarbonyl diimidazole. Treatment of 3 with hydroxylamine and removal of the DMB group with trifluoroacetic acid gave 1. N-Hydroxythiourea (1) showed no activity in the L1210 mouse tumor.

Animals↗