Reinhard Brossmer

Inhibition of platelet aggregation and the platelet release reaction by α, ω diadenosine polyphosphates

The aggregation of human blood platelets by adenosine diphosphate (ADP) is specifically inhibited by adenosine and a few related compounds [l-3]. While the mode of action of adenosine remains controversial, investigations have been made with various adenosine analogues [4]. The present report is of studies with a series of adenosine derivatives which have not been tested previously with this system. This group of substances contain adenosine molecules joined in pairs, by different numbers of phosphate groups, at position 5’ of the two ribosyl moieties. They may be represented by the formula:

Synthesis of N-formyl- and N-succinyl-D-neuraminic acid on the specificity of neuraminidase.

The sialic acids are important constituents of numerous glycoproteins, glycolipids, and oligosaccharides. Little is known about their functional signifp cance for the biological effect of these complex substances. In many instances removal of sialic acid is accompanied by a loss of biological activity [I] . So far only N-acetylneuraminic acid (lactaminic acid) and N-glykolylneuraminic acid were found in nature together with 0-acetylated derivatives. The terminal sialyl moiety seems always to be bound to the next carbohydrate unit by an ar-ketosidic bond. Ample evidence has now been accumulated that only this type of linkage is split by the various neuraminidase enzymes. We were interested in obtaining a sialic acid with two anionic sites in the molecule and chose the succinyl group as N-substituent. Furthermore it seemed worthwhile to prepare a sialic acid with a Cl residue at the amino group. In this communication we describe the synthesis of N-formyl and N-succinyl-D-neuraminic acid and of their corresponding benzyl &ketosides. In addition we wish to report the result of the interaction between Vibrio cholerae neuraminidase and the above mentioned ketosides. It was found that the benzyl-ketoside of N-succinylneuraminic acid is not split at all by the enzyme. This result could be expected, since the N-butyryl group also abolishes the property to serve as substrate PIOn the other hand the enzyme cleaves the corresponding ketoside of N-formylneuraminic acid. However, compared to the naturally occurring 3-O-N-

Purification and characterization of human chorionic gonadotropin.

Several investigators [2-71 have previously attempted to purify human chorionic gonadotropin (HCG). These methods proved to be either too time consuming, not reproducible, or limited to small quantities. In addition, these purified products are difficult to compare because of differences in the methodology of biological and physico-chemical measurements. This paper describes a simple and fast chromatographic method for the preparation of this glycoprotein hormone in a highly purified form. Its characterization was achieved by physico-chemical, biological and immunological methods. The following report deals with the chemical modifications of HCG at specific sites. It provides some information about the importance of certain parts of the molecule for the biological and immunological activity.

Zum Mechanismus der Thrombozytenaggregation I

Die grol3e Bedeutung der sog. Klebrigkeit von Thrombozyten fiir den Mechanismus der Thrombogenese (und Infarktneigung) ist bekannt. Zahlreiche Substanzen, z. 13. Kollagen, Fett, Thrombin, Adrenalin, Serotonin, Trittthyl-Zinn verm6gen die Aggregation zu induzieren. Der eigentliche Mechanismus ist jedoch unklar. Eine zentrale Rolle wurde in letzter Zeit dem Adenosindiphosphat (ADP) [1] zugeschrieben, das durch viele Stoffe, z.B. durch die erw~thnten Substanzen im

Inhibition of ADP-Induced Platelet Aggregation by Adenosine Tetraphosphate

In contrast to previous reports, highly purified adenosine tetraphosphate (AP4) does not induce the aggregation of platelets but inhibits the aggregation and release reaction in platelet-rich plasma promoted by ADP. The inhibitory action of AP4 on the aggregation by ADP is compared with that of AMP and ATP. The data presented suggest a competitive manner of inhibition of the ADP-induced aggregation by AP4.

Chemical modification of human chorionic gonadotropin and its biological and immunological characterization

In the preceding paper [I] we describe a simple chromatographic method which can be easily reproduced for preparation of a highly purified human chorionic gonadotropin (HCG), which nevertheless separated in starch gel electrophoresis without urea and in polyacrylamide electrophoresis with urea into 5-7 bands, respectively. This report deals with chemical modifications of the highly purified glycoprotein hormone, giving some information about the prerequisites for its biological and immunological active site.

Modelluntersuchungen und neue Gesichtspunkte zum Mechanismus der Thrombozytenaggregation

Der Mechanismus der Thrombozytenaggregat ion ist trotz zahlreicher Untersuchungen immer noch ziemlich unklar. Im allgemeinen wird heute die Meinung vertreten, dab ftir den Ablauf der Aggregation neben funktionstiichtigen Pl~ttchen mindestens noch drei Faktoren, n~mlich Kalzium, Adenosindiphosphat und ein noch nicht einheitlich definierter Plasmafaktor unbedingt notwendig seien, um eine Verklumpung yon Thrombozyten herbeizuftihren. An Hand der folgenden Abbildungen m6chte ich versuchen Ihnen zu zeigen, dab auch ohne Anwesenheit dieser genannten Faktoren eine Thrombozytenaggregation m6glich ist, und zwar unter dem Einflug geladener Makromolekiile. Bis jetzt vorliegende Ergebnisse weisen darauf bin, dab elektrostatische Krfifte bei der Verklumpung von Blutpl~ttchen offenbar eine bedeutende Rolle spielen und dab Stoffwechselprozesse oder enzymatische Vorgiinge dabei wahrscheinlich nicht beteiligt sin& Besonders interessant ist, dab sich aus unseren Untersuchungen Ansatzpunkte zur Verminderung einer erh6hten Klebrigkeitstendenz yon Blutpl/ittchen zu ergeben scheinen.

Über 5-Hydroxymethyl-cytidin und 5-Hydroxymethyl-cytosin-N-3-β-D-glucopyranosid sowie über reaktionsfähige Vorstufen

5-Benzyloxymethyl-NNH2-benzoyl-cytosine (4) is formed from 5-hydroxymethyl-cytosine (1) in 80% yield by benzylation and subsequent benzoylation. The benzylation readily takes place with benzyl alcohol and catalytic amounts of hydrochloric acid in tetrahydrothiophen-1.1-dioxide as solvent. — 4 is quantitatively converted in pyridine at room temperature to a toluene soluble mercury (II) salt 5. 5 condenses easily with 2.3.5-tribenzoyl-D-ribofuranosyl chloride to give the β-nucleoside 6, no a-anomer being found. — The removal of all protecting groups by catalytic hydrogenation and treatment with sodium methoxide or ammonia leads to cristalline 5-hydroxymethyl cytidine 10 (ca. 60% yields based on 1). — In an analogous manner N-3-β-D-glucosyl-5-hydroxymethyl-cytosine 15 is prepared. — Selective removal of certain of the protecting groups in 6 and 11 yields potentially valuable synthetic intermediates.