Unusual amidation reaction of asparagine-containing glycopeptide antibiotics in the presence of (benzotriazole-1-yl)oxy-tris(pyrrolidino)phosphonium hexafluorophosphate (PyBOP)

The coupling reagent (benzotriazole-1-yl)oxy-tris(pyrrolidino)phosphonium hexafluorophosphate (PyBOP) is widely used for the synthesis of different peptides and their amides, particularly carboxamides of glycopeptide antibiotics of the vancomycin or teicoplanin groups. The amidation reaction of the carboxyl group of the seventh amino acid residue (AA7) in antibiotics in the presence of PyBOP is not usually accompanied by the formation of significant amounts of byproducts. However, the amidation of eremomycin (I) with bulky amines (e.g., decyl amine and adamantyl amine) in the presence of PyBOP at pH ～8.5 (Et₃N or (i-Pr)₂EtN) yielded N-unsubstituted carboxamide of eremomycin (Ia) as an admixture. The interaction of asparagine-containing antibiotics (eremomycin or vancomycin) with the excess of PyBOP and Et₃N (pH ～8.5) in the absence of amine or ammonia led to the formation of still larger amounts of corresponding unsubstituted AA7-amides (～20%). Their structure was determined by ¹H NMR and ESI MS methods and confirmed by comparing with authentic samples. It is assumed that the amide group of the asparagine residue (AA3) is the source of ammonia in the unususal amidation reaction of Asn-containing antibiotics.     

Uncharged P-selectin blockers

The blocking potency of P- and L-selectin was studied for certain small molecule mannosides and their polyacrylamide (PAA, 30 kDa) conjugates in comparison to SiaLe(x) and fucoidan. Two experimental systems were used: (1) solid phase static assay based on recombinant selectins, and (2) P-selectin dependent rat peritoneal inflammation. betaMan-SC6H4NO2- p was four times more potent P-selectin inhibitor as compared to SiaLe(x). Docking of this molecule onto the P-selectin carbohydrate-binding site demonstrated that a nitro group enabled an electrostatic interaction with residue Lys 84, while the phenyl ring and the CH2 at C-6 contacted the CH2 groups of the same Lys residue. In vivo, betaMan-SC6H4NO2- p blocked experimental inflammation better than SiaLe(x), but significantly lower than fucoidan. In vitro Man-polyacrylic acid conjugates appeared to be very potent inhibitors comparable to fucoidan, uncharged Man-PAA proved rather active, comparable to SiaLe(x)-PAA both in vitro, and in vivo, whereas mannan did not display any P-selectin blocking effect.     

Study of 1-deoxy-1-(indol-3-yl)-L-sorbose, 1-deoxy-1-(indol-3-yl)-L-tagatose,and their analogs

Alkaline degradation of the ascorbigen 2-C-[(indol-3-yl)methyl]-alpha-L-xylo-hex-3-ulofuranosono-1,4-lactone (1a) led to a mixture of 1-deoxy-1-(indol-3-yl)-L-sorbose (2a) and 1-deoxy-1-(indol-3-yl)-L-tagatose (3a). The mixture of diastereomeric ketoses underwent acetylation and pyranose ring opening under the action of acetic anhydride in pyridine in the presence of 4-dimethylaminopyridine (DMAP) with the formation of a mixture of (E)-2,3,4,5,6-penta-O-acetyl-1-deoxy-1-(indol-3-yl)-L-xylo-hex-1-enitol (4a) and (E)-2,3,4,5,6-penta-O-acetyl-1-deoxy-1-(indol-3-yl)-L-lyxo-hex-1-enitol (5a), which were separated chromatographically. Deacetylation of 4a or 5a afforded cyclised tetrols, tosylation of which in admixture resulted in 1-deoxy-1-(indol-3-yl)-3,5-di-O-tosyl-alpha-L-sorbopyranose (12a) and 1-deoxy-1-(indol-3-yl)-4,5-di-O-tosyl-alpha-L-tagatopyranose (13a). Under alkaline conditions 13a readily formed 2-hydroxy-4-hydroxymethyl-3-(indol-3-yl)cyclopenten-2-one (15a) in 90% yield. Similar transformations were performed for N-methyl- and N-methoxyindole derivatives.     

Annual Changes in Meiobenthos Community Structure in Alekseev Bight, Sea of Japan

We performed a comparative analysis of the taxonomical composition and population density of the meiobenthos and substrate types of Alekseev Bight, Sea of Japan, throughout the period when a plantation for mariculture of Japanese scallop was exploited in the bight and for a decade after the plantation had been removed. We found that silting of substrates in the bight decreased and the number of taxonomical groups that constituted the meiobenthos increased. The nematodes that, earlier, dominated the meiobenthos in terms of population density were later exceeded by foraminiferans, the species diversity of which increased. Changes are revealed in the composition of the dominant species of these groups.     

Immobilization of chloroperoxidase from Serratia marcescens in semi-permeable protein membranes

A method for the immobilization of chloroperoxidase from the bacterial strain Serratia marcescens in semi-permeable membranes was developed based on the following proteins: bovine serum albumin, gelatin, ribonuclease, cytochrom C, and the protein of the covering layer of Bacillus sphaericus cells. Estimation of the activity and stability of immobilized preparations in a batch reactor was carried out. Published in Russian in Prikladnaya Biokhimiya i Mikrobiologiya, 2006, Vol. 42, No. 2, pp. 152–155. This article was translated by the authors.     

C-terminal lysosome targeting domain of CD63 modifies cellular localization of rabies virus glycoprotein

The glycoprotein of rabies virus is the central antigen elicited the immune response to infection; therefore, the majority of developing anti-rabies vaccines are based on this protein. In order to increase the efficacy of DNA immunogen encoding rabies virus glycoprotein, the construction of chimeric protein with the CD63 domain has been proposed. The CD63 is a transmembrane protein localized on the cell surface and in lysosomes. The lysosome targeting motif GYEVM is located at its C-terminus. We used the domain that bears this motif (c-CD63) to generate chimeric glycoprotein in order to relocalize it into lysosomes. Here, it was shown that, in cells transfected with plasmid that encodes glycoprotein with c-CD63 motif at the C-terminus, the chimeric protein was predominantly observed in lysosomes and at the cell membrane where the unmodified glycoprotein is localized in the endoplasmic reticulum and at the cell surface. We suppose that current modification of the glycoprotein may improve the immunogenicity of anti-rabies DNA vaccines due to more efficient antibody production.     

Anthracycline antibiotics and their derivatives,inhibitors of topoisomerase I

The relationship between the structure of new semisynthetic derivatives of doxorubicin, daunorubicin, and carminomycin and their ability to inhibit topoisomerase I were studied. The new derivatives inhibit the activity of topoisomerase I at low concentrations, induce the death of K-562 leukemia cells in culture, and produce an antitumor effect in experimental animals bearing P388 leukemia.     

Hydrolysis of Phosphoester Bond by the Heme-Independent Chloroperoxidase from Serratia marcescens

Heme- and metal-independent chloroperoxidase from Serratia marcescens W 250 is shown to be capable of catalyzing the p-nitrophenyl phosphate hydrolysis. The parameters of the phosphatase reaction are determined and inhibitors and activators of the process are found. A hypothetical mechanism of the hydrolysis of phosphoesters by heme- and metal-independent haloperoxidases is suggested.     

Anticoagulant activity of fucoidans from brown algae

The anticoagulant activity of polysaccharide fucoidans from 11 species of brown algae was studied. The anticoagulant activity was measured by the activated partial thromboplastin time (APTT), prothrombin time, and thrombin time. Inhibitory action of these fucoidans significantly varied from one species to another. Fucoidans from Laminaria saccharina and Fucus distichus exhibited high anticoagulant activity, while fucoidans from Cladosiphon okamuranus and Analipus japonicus were almost inactive. Other fucoidans exhibited intermediate inhibitory activity. The inhibitory effect of fucoidans on thrombin and factor Xa was investigated in the presence or in the absence of natural thrombin inhibitor, antithrombin III (AT III). In contrast to the best-studied anticoagulant, heparin, most of these fucoidans inhibited thrombin in the absence of AT III. In the presence of AT III the inhibitory effect of fucoidans considerably increased. In contrast to heparin, fucoidans weakly influenced factor Xa activity in the presence of AT III and their inhibitory effect was not observed in the absence of AT III. There was no correlation between the anticoagulant activities of this series of fucoidans and their anti-inflammatory action, studied earlier. It is suggested that these two types of fucoidan activities depend on different structural features of fucoidans. Results of this study demonstrate a possibility of preparation of fucoidans with high anti-inflammatory activity but low anticoagulant activity. Anticoagulant activity of the fucoidans did not exhibit direct dependence on the content of fucose, the other neutral sugars and sulfates; no dependence was also found between the anticoagulant activity and the structure of the backbone of their molecules.     

Synthesis and cytotoxic properties of 4,11-bis[(aminoethyl)amino]anthra[2,3-b]thiophene-5,10-diones,novel analogues of antitumor anthracene-9,10-diones

We developed the synthesis of a series of thiophene-fused tetracyclic analogues of the antitumor drug ametantrone. The reactions included nucleophilic substitution of methoxy groups in 4,11-dimethoxyanthra[2,3-b]thiophene-5,10-diones with ethylenediamines, producing the derivatives of 4,11-diaminoanthra[2,3-b]thiophene-5,10-dione in good yields. Several compounds showed marked antiproliferative potency against doxorubicin-selected, P-glycoprotein-expressing tumor cells and p53^?/? cells. The cytotoxicity of some novel compounds for P-glycoprotein-positive cells is highly dependent on N-substituent at the terminal amino group of ethylenediamine moiety. The cytotoxic potency of selected compounds correlated with their ability to attenuate the functions of topoisomerase I and telomerase, strongly suggesting that these enzymes are the major targets of antitumor activity of anthra[2,3-b]thiophene-5,10-dione derivatives.