Synthesis of a 200-member library of squaric acid N-hydroxylamide amides

We report here the parallel synthesis of 200 compounds based on squaric acid template. These compounds are obtained via a one-step solution-phase procedure starting from three squaric acid N-hydroxylamide esters precursors. The set of diverse reagents qualified (amines, anilines, amino-alcohols and amino-esters) makes this strategy suitable for the search of biologically active compounds. The library was screened on the zinc metalloenzyme ADAMTS-5 and hits with IC(50) in the range of 1-50 microM were identified.     

Conjugation of p-aminophenyl glycosides with squaric acid diester to a carrier protein and the use of neoglycoprotein in the histochemical detection of lectins

The coupling of p-aminophenyl 2-acetamido-2-deoxy-3-O-beta-D- galactopyranosyl-beta-D-galactopyranoside (gal-beta 1,3-galNAc) to bovine serum albumin (BSA) was achieved by using 1,2-diethoxycyclobutene-3,4-dione (squaric acid diester) as a new coupling reagent. Two selective consequential steps afforded the desired neoglycoprotein: reaction of the p-aminophenyl group of gal-beta 1,3-galNAc with squaric acid diester gave the corresponding squaric acid amide ester, which was transformed into the BSA conjugate by coupling with the lysyl epsilon-amino group of BSA through formation of a squaric acid 1,2-bisamide. The experimental conditions for the reactions and the optimization of average were performed by using p-anisidine as model substance, the methyl group substituting for the carbohydrate part of a p-aminophenylglycoside. Neoglycoproteins have proven to be valuable tools for lectin detection. To evaluate the properties of this type of probe, the obtained neoglycoprotein with the histochemically crucial T-antigen structure was used for glycocytological and glycohistochemical studies. Three cultured human tumor cell lines and tissue sections from human breast carcinomas were chosen. Its efficiency was similar in comparison to measurements with a probe, derived by diazotization with the p-aminophenyl glycosides of gal-beta 1,3-galNAc and already shown to be a reliable marker for lectin localization in tissue sections and cultured cells.     

Modulating weak intramolecular interactions through the formation of beryllium bonds: complexes between squaric acid and BeH2

The electronic structure of the two most stable isomers of squaric acid and their complexes with BeH₂ were investigated at the B3LYP/6-311?+?G(3df,2p)// B3LYP/6-31?+?G(d,p) level of theory. Squaric acid forms rather strong beryllium bonds with BeH₂, with binding energies of the order of 60 kJ?mol^?1. The preferential sites for BeH₂ attachment are the carbonyl oxygen atoms, but the global minima of the potential energy surfaces of both EZ and ZZ isomers are extra-stabilized through the formation of a BeH···HO dihydrogen bond. More importantly, analysis of the electron density of these complexes shows the existence of significant cooperative effects between the beryllium bond and the dihydrogen bond, with both becoming significantly reinforced. The charge transfer involved in the formation of the beryllium bond induces a significant electron density redistribution within the squaric acid subunit, affecting not only the carbonyl group interacting with the BeH₂ moiety but significantly increasing the electron delocalization within the four membered ring. Accordingly the intrinsic properties of squaric acid become perturbed, as reflected in its ability to self-associate.

On limited platinum chains. Synthesis and crystal structure of a green tetranuclear platinum compound,cis-diammine tetraplatinum squarate,Pt4(NH3)8(C404)4· 4H20. A structural analogue of platinum blues

From the reaction of the cis-dichlorodiammine hydrolysis product with squaric acid, green crystals of cis-diammine tetraplatinum squarate are obtained. A single crystal X-ray diffraction analysis shows that the compound consists of a tetranuclear chain, whose adjacent platinum atoms are bridged by squaric ligands.     

手性环方铂络合物与DNA相互作用中的分子识别

用生物微量热技术及ＤＮＡＴｍ测量研究了手性不同的三种环方铂络合物与小牛胸腺ＤＮＡ（２００ｂｐ）作用中的特异性,发现Ｒ,Ｒ构型的与ＤＮＡ作用最强,这与癌细胞的体外筛选结果相一致．而且通过ＨＰＬＣ及１３Ｃ－ＮＭＲ研究为环方铂络合物与ＤＮＡ作用的分子机理分析找到了直接的证据．     

Didecyl squarate--a practical amino-reactive cross-linking reagent for neoglycoconjugate synthesis

The present paper describes the synthesis and use of the hydrophobic squaric decyl ester glycosides in neoglycoconjugate chemistry. The 2-aminoethyl glycosides of -D-mannopyranose, lactose, globotriose, globotetraose, GM3, and sialyl Lewis^x, as well as the 2-(2-aminoethylthio)ethyl glycoside of -D-mannopyranose, -D-glucopyranose, and galabiose were reacted with squaric acid didecyl ester to afford the hydrophobic squaric decyl ester glycosides. These glycosides were efficient reagents for the conjugation to amino-functional microtiter plates, BSA and aminated Sepharose EAH 4B. The decyl ester moiety of the squaric decyl ester glycosides constitutes a traceless hydrophobic tag, which has the major advantage, as compared to the corresponding ethyl esters, that it enables easy purification of the glycosides with silica chromatography and that unreacted excesses glycosides from conjugation reaction mixtures can easily be recovered by means of C18 solid phase extraction.     

串珠镰刀菌素的结构与毒性的关系

用O_3对串珠镰刀菌素去毒处理后,对产物进行了分离纯化,并通过红外、核磁共振等分析,证明串珠镰刀菌素双键消失,四元环已打开,产物为2,3-二羟基-2,3环氧-丁二酸(3)和2-羰基-3-羟基-丁二酸(4).以1日龄北京雏鸭为实验动物,将串珠镰刀菌素及其结构类似物方酸进行生物毒性对比试验,分别灌胃法给毒8mg/kg体重和方酸24mg/kg体重,方酸量为串珠镰刀菌素的三倍时仍无毒性,说明串珠镰刀菌素结构中的H对其毒性起关键作用.这在国内外尚属首次报道.     

Exploring alternative Zn-binding groups in the design of HDAC inhibitors: squaric acid, N-hydroxyurea, and oxazoline analogues of SAHA

Analogues of suberoylanilide hydroxamic acid (SAHA) were prepared by replacing the Zn-binding group with squaric acid, N-hydroxyurea, and 4-hydroxymethyl oxazoline units, also varying the length of the aliphatic chain. No inhibitory activity on HDAC was observed below 1.0 microM and no cytotoxic activity on different tumor cell lines was seen below 20.0 microM.     

Novel paramagnetic macromolecular complexes derived from the linkage of a macrocyclic Gd(III) complex to polyamino acids through a squaric acid moiety

Macromolecular Gd(III) complexes may find useful application as contrast agents for magnetic resonance angiography (MRA). Herein two novel systems are reported, namely Gd(DO3ASQ)3-lys16 and Gd(DO3ASQ)30-orn114. Their syntheses are based on the ability of the squaric acid moiety to act as a linker between the DO3A (1,4,7, 10-tetraazacyclododecane-1,4,7-triacetic acid) chelate moiety and the polyamino acidic chain. Moreover, the squaric acid participates in the coordination cage of the Gd(III) ion. The investigation of 1H and 17O NMR relaxation processes of solvent water nuclei allowed a detailed characterization of the systems under study. Gd(DO3ASQ)30-orn114 displays a remarkable ability to enhance the water proton relaxation rate of its solutions, and it may be considered as potential contrast agent for MRA applications.     

The synthesis and characterization of copper(II) squarate chloride

Copper(II) squarate chloride [Cu(H₂C₄O₄)(Cl)]₂, C₃H₇OH has been synthesized by reacting propan- 2-ol solutions of CuCl₂•2H₂O and squaric acid in an inert atmosphere. The complex has been characterized by elemental analysis, spectral analysis and magnetic measurements.     

Investigation on glyoxalase I inhibitors

Several classes of compounds - flavones, coumarins, S- and N-substituted glutathione analogs, transition state analogs, porphyrins, nucleotides and nucleosides - have been reported to inhibit the enzyme gloxalase I. In the current study, examination of some of the aforementioned compounds has revealed that squaric acid does not function as an inhibitor of glyoxalase I and several other compounds are much less effective in this regard than previously reported. Several new potent inhibitors of yeast glyoxalase I have been identified. Compounds containing the tropolone structure were especially inhibitory. Glutathione adducts of benzoquinone and naphthoquinone were also inhibitory and may be of particular interest with regard to the toxicology of normal aromatic metabolites in vivo.     

Simple, direct conjugation of bacterial O-SP-core antigens to proteins: development of cholera conjugate vaccines

Bacterial O-SP-core antigens can be conjugated to proteins in the same, simple way as synthetic, linker-equipped carbohydrates by applying squaric acid chemistry. Introduction of spacers (linkers) to either O-SP-core antigens or protein carriers, which is involved in commonly applied protocols, is not required. The newly developed method described here consists of preparation of a squaric acid monoester derivative of O-SP-core antigen, utilizing the amino group inherent in the core, and reaction of the monoester with the carrier protein. The intermediate monoester can be easily purified; its conjugation can be monitored by SELDI-TOF mass spectrometry and, thus, readily controlled, since the conjugation can be terminated when the desired carbohydrate-protein ratio is reached. Here, we describe production of conjugates containing the O-SP-core antigen of Vibrio cholerae O1, the major cause of cholera, a severe dehydrating diarrheal disease of humans. The resultant products are recognized by convalescent phase sera from patients recovering from cholera in Bangladesh, and anti-O-SP-core-protein responses correlate with plasma antilipopolysaccharide and vibriocidal responses, which are the primary markers of protection from cholera. The results suggest that such conjugates have potential as vaccines for cholera and other bacterial diseases.     

Synthesis of a globotetraose trimer

The synthesis is described of a globotetraose trimer in 74% yield by the reaction of tris(2-aminoethyl)amine with the hydrophobic squaric decyl ester glycoside of globotetraose. The synthesis was readily monitored and purified using reversed phase HPLC. Unreacted squaric decyl ester globotetraoside was recovered rendering the method highly economical.     

河南蹄叶橐吾根的化学成分研究

从蹄叶橐吾根乙醇提取物中分离得到11种化合物,经理化和波谱分析分别鉴定为原儿茶醛(1)、7-羟基-色原酮(2)、咖啡酸(3)、阿魏酸(4)、1,5-二咖啡酰奎宁酸(5)、当归酸(6)、β-谷甾醇(7)、胡萝卜苷(8)、蜂斗菜素(9)、异蜂斗菜素(10)及正三十五烷(11)。其中酚类化合物1～5、倍半萜类化合物9～10及脂烃11为首次从该植物中分离得到。     

A highly efficient preparation of neoglycoconjugate vaccines using subcarriers that bear clustered carbohydrate antigens

A limited amount of spacer-equipped carbohydrate haptens was linked by reductive amination to a subcarrier, an oligopeptide containing 16 amino groups, to give a hapten-carrying subcarrier (HCS). It was then linked, via the remaining free amino groups, to chicken serum albumin (CSA) to give a cross-linked neoglycoconjugate bearing the haptens in the form of clusters. Alternatively, the same type of a glycoconjugate, but with higher conjugation efficiency, was obtained when HCS was treated successively with squaric acid diethyl ester and CSA.     

Synthesis of structured lipids and etherlipids with antioxidants: combination of a selena fatty acid and a selena fatty alcohol with a carotenoic acid in glyceride molecules

Selenium and carotenoids show similar and complementary properties and protect against a variety of pathological processes. Mixtures of both compounds are found in nutritional supplements and are used to prevent several diseases. The synthetic connection of carotenoids with selenium in glycerols may increase the chemopreventive activity of the individual compounds. Beta-apo-8'-carotenoic acid and 7-selenacapryloic acid were esterified with glycerol to highly unsaturated stable di- and triglycerides. Intramolecular selenium:carotenoid ratios of 1:1, 2:1 and 1:2 were obtained for 1-(7-selenaoctanoyl)-3-(3beta-apo-8 -carotenoyl)-glycerol, 1,3-di-(beta-apo-8'-carotenoyl)-2-(7-selenaoctanoyl)-glycero l and 1,2-di-(7-selenaoctanoyl)-3-(beta-apo-8'-carotenoyl)-glycero l, respectively. The carotenoic acid was likewise connected to the pharmacologically interesting 11-selenalaurylglycerolether forming an alkyl-acylglyceride: 1-(11-selenadodecyl)-3-(beta-apo-8'-carotenoyl)-glycerol.     

Antibody catalyzed hydrolysis of a quorum sensing signal found in Gram-negative bacteria

N-(3-Oxo-acyl) homoserine lactones are used by Gram-negative bacteria to signal the establishment of specific population densities and coordinate population-wide gene expression. Herein we report the antibody-catalyzed hydrolysis of N-(3-oxo-acyl) homoserine lactone (AHL) using a reactive immunization strategy with a squaric monoester monoamide hapten. Kinetic analysis of the most efficient antibody revealed a modest k(cat), with AHL hydrolysis competitively inhibited by original squaric monoester monoamide hapten. These studies suggest that antibody catalysis could provide a new avenue for blocking quorum sensing in bacteria.     

Metabolism of prostaglandins D2 and F2 alpha in primary cultures of rat hepatocytes

3H-Labeled prostaglandins D2 and F2 alpha rapidly degraded to more-polar metabolites in primary cultured rat hepatocytes. The metabolites of prostaglandins D2 and F2 alpha accumulated in the culture medium. The metabolites extracted by ethyl acetate at pH 3 were purified by silicic acid column and thin-layer chromatography of silica gel, and were analysed by gas chromatography-mass spectrometry. The major metabolites from prostaglandin D2 were identified as dinor-prostaglandin D1 (7 alpha,13-dihydroxy-9-ketodinorprost-11-enoic acid) and tetranor-prostaglandin D1 (5 alpha,11- dihydroxy-7-ketotetranorprost-9-enoic acid). Those from prostaglandin F2 alpha were identified as dinor-prostaglandin F1 alpha (7 alpha,9 alpha,13-trihydroxydinorprost-11-enoic acid), tetranor-prostaglandin F1 alpha (5 alpha,7 alpha,11-trihydroxytetranorprost-9-enoic acid) and 9 alpha,11 alpha,15-trihydroxyprost-13-ene-1,20-dioic acid. These data indicate that prostaglandins D2 and F2 alpha mainly degraded by beta-oxidation, which is the same process as reported earlier for prostaglandins E1 and E2, and that prostaglandin F2 alpha was also subjected to omega-oxidation.     

肋果茶中的萜类化学成分研究

从肋果茶(Sladenia celastrifolia)95％乙醇提取物的乙酸乙酯部位中分离得到15个萜类化合物,经波谱学方法分别鉴定为sladeniafolin A(1),grasshopper ketone (2),(3S,5R,6S,7E,9R) -7-megastigmene-3,6,9-triol (3),hedytriol (4),(3S,5R,6R,7E,9R) -3,5,6,9-tetrahydroxy-7-megastigmene(5),1′S*,4′R*-8-(4′-hydroxy-2′,6′,6′-trimethylcyclohex-2-enyl)-6-methyloct-3E,5E,7E-trien -2-one (6),2α,3α,19α,23-tetrahydroxyurs-12-en-28-oic acid (7),2α,3β,19α,23-tetrahydroxyurs-12-en-28-oic acid(8),pomolic acid(9),3-O-acetyl pomolic acid(10),ursaldehyde (11),camarolide (12),3β-hydroxyurs-11-en-13β(28) -olide (13),3β-hydroxy -11α,12α-epoxy-urs-13β,28-olide (14)和28-0-β-D-glucopyranosyl euscaphic acid (15).以上化合物均首次从该植物中分离得到,其中1为新的C9裂环烯醚萜.     

Positional distribution of isomers of monoenoic fatty acids in animal glycerolipids

The distributions of the following monoenoic acids were determined [notation: (position of double bond)-(chain length): (no. of double bonds)]: 7-, 9-, and 11-16:1; 7-, 9-, 11-, and 13-18:1; 9-, 11-, and 13-20:1; 9 + 11-22:1 and 13-22:1. As a rule, all isomers of a group show different distribution patterns. In the phospholipids of fish and mammals, the 7- and 13-isomers of 18:1 accumulate in position 1. In triglycerides of mammals fed on fish they accumulate in positions 1 plus 3, and this distribution is shared by 7-16:1 and 11-16:1 and by the groups 20:1 and 22:1. The positional distribution of the acids seems to depend on their structure, the 9-isomers in general accumulating in position 2; but in triglycerides, at least, the origin of the acid also seems to play a directing role, the exogenous acids being incorporated into positions 1 and 3. The variability of the distribution patterns of 9-16:1, 9-18:1, and 11:18:1, which contrasts with the regularity of the patterns for saturated and polyenoic acids, may be connected with the ability of the endogenous monoenoic acids to balance fluctuations in the supply of the exogenous polyenoic acids, and with the role of the fatty acid 9,10-dehydrogenation mechanism in the maintenance of structural and physical properties of phospholipids and triglycerides.