M. Zaoral

Immunoadjuvant activity of synthetic N-acetyl muramyl dipeptide.

The administration of phosphatidyl choline/cholesterol liposomes with entrapped N-acetyl muramyl dipeptide induced in guinea-pigs the development of delayed hypersensitivity to ovalbumin.

The synthesis of O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→4)-N-acetylnormuramoyl-l-α-aminobutanoyl-d-isoglutamine☆

Abstract Benzyl 2-acetamido-3- O -allyl-6- O -benzyl-2-deoxy-4- O -(3,4,6-tri- O -acetyl-2-deoxy-2-phthalimido-β- d -glucopyranosyl)- α- d -glucopyranoside ( 4 ) was obtained in high yield on using the silver triflate method in the absence of base. Compound 4 was converted in six steps into benzyl 2-acetamido-4- O -(2-acetamido-3,4,6-tri- O -benzyl-2-deoxy-β- d -glucopyranosyl)-6- O -benzyl-3- O -(carboxymethyl)-2-deoxy-α- d - glucopyranoside, which was coupled with the benzyl ester of l -α-aminobutanoyl- d -isoglutamine and the product hydrogenolyzed to afford the title compound. O -Benzylation of benzyl 2-acetamido-4- O -(2-acetamido-2-deoxy-β- d -glucopyranosyl)-3- O -allyl-6- O -benzyl-2-deoxy-α- d -glucopyranoside with benzyl bromide and barium hydroxide in N,N -dimethylformamide is strongly exhanced by sonication of the reaction mixture.

Structure specificity of some immunoadjuvant synthetic glycopeptides

The immunoadjuvant activity of muramyl dipeptide seems to be critically dependent on the type of substitution of the γ-carboxyl group of the D-isoglutamine residue. Moreover the nonapeptide L-Ala-D-isoGlu-L-Lys-D-Ala-(Gly)5-OME also shows a definite effect.

DDAVP (Desmopressin) and solid phase peptide synthesis.

F orty years ago I had a good chance to stay for 9 months (1967–1968) in the laboratory of the inventor of the revolutionary solid-phase peptide synthesis (SP synthesis), the late Prof. R.B. Merrifield, at the Rockefeller University, New York. The stay was extremely interesting for me. SP synthesis had not been generally accepted during those years. Besides getting acquainted with the art of the SP synthesis, I witnessed a number of heated and most interesting as well as instructive discussions between supporters and opponents of the method. The cause of the controversy clearly rooted in an excessive optimism of the first communications on SP synthesis. The method opened the way for the preparation of peptides for many researches, but not for all of them. At the 19th European Peptide Symposium in Greece, R.B. Merrifield said: ‘‘You must know how to do it properly.’’ After homecoming, my group at the Institute of Organic Chemistry and Biochemistry of the Czechoslovak Academy of Sciences started introducing SP synthesis into laboratory and production practice. We proceeded with a considerable caution, as the Institute’s climate was ill disposed toward SP synthesis at that time. Our aim was an SP synthesis of DDAVP (laboratory abbreviation for [1-mercaptopropionic acid, 8-D-arginine]vasopressin, main commercial name Desmopressin), as an easier, shorter, and more economical alternative to the solution synthesis. We have fulfilled this task and have carefully compared DDAVP products obtained by both methods. They were found quite identical and undistinguishable from each other. This finding was very important for us at that time. The SP synthesis of DDAVP was later realized in practice and in years 1976–1999, the compound was produced using this method in the then Czechoslovakia. DDAVP has found rather broad application in medical practice as a homeostatic and hemostatic drug, in clinical diagnostics and in thousands of biochemical and pharmacological studies. Scientific literature contains under the key words ‘‘DDAVP’’ and ‘‘Desmopressin’’ well over 3000 quotations so far. The SP synthesis of DDAVP can thus be, for good reasons, held as an important practical application of the Merrifield method.

Pharmacology of oxytocin-(1-6)-hexapeptide amide, vasopressin-(1-6)-hexapeptide amide and their deamino analogues.

Abstract Oxytocin-(1 -6)-hexapeptide amide and vasopressin-(1 -6)-hexapeptide amide had lower activities than the parent hormones on the isolated rat uterus and in the antidiuretic assay in hydrated rats; none of the analogues had pressor activity. Deamination of both rings increased uterotonic activity. The uterotonic effect of the analogues was blocked by N-carbamoyl-2-O-methyloxytocin, a competitive inhibitor of oxytocin, which proved their action to be specific. Mg2+ did not potentiate the effect of the ring molecules on the isolated uterus.

Blood-platelets-damaging activity of some synthetic streptococcus peptidoglycan subunits and analogues

A series of 25 synthetic subunits or analogues of streptococcal peptidoglycan was tested for their ability to damage rabbit blood platelets. The morphological changes of the platelets were studied on an ultrastructural level. Minimal subunit structure able to produce a complete lysis of the platelets was found to be muramyldipeptide (MDP). Comparable lysis of platelets was also caused by muramyltetrapeptide and MDP containing D-Ala instead of L-Ala. The lytic effect was dose-dependent and was exhibited rather after high doses of the substances used (up to 500 micrograms/ml). For the lytic reaction, the configuration of C3 and C4 in the muramyl residue of MDP was essential. Many substances produced only degranulation without lysis of the platelets and some of them did not influence the platelet ultrastructure at all. The paper presents some structure-to-function relationships of the compounds and shows that the platelet-damaging activity of peptidoglycan may be related to certain portions of the peptidoglycan molecule. This activity should be tested when the immunomodulatory substances derived from the bacterial peptidoglycan are searched for.