Synthesis and kinetic evaluation of 4-deoxy-4-phosphonomethyl-d-erythronate, the first hydrolytically stable and potent competitive inhibitor of ribose-5-phosphate isomerase

4-deoxy-4-Phosphonomethyl-d-erythronate, an isosteric and hydrolytically stable analogue of the known ribose-5-phosphate isomerase inhibitor 4-deoxy-4-phospho-d-erythronate, was obtained by a 14-step synthesis from d-arabinose through an highly improved synthesis of the precursor 5-deoxy-5-phosphonomethyl-d-arabinose. The title compound appears as the first stable and potent competitive inhibitor of the enzyme catalyzed isomerization of ribose-5-phosphate to d-ribulose-5-phosphate (K_i=74 μM, K_m/K_i=100), exhibiting only a 3-fold weaker inhibitory activity than its phosphate analogue.     

甲烷在Mo/HZSM-5催化剂上的脱氢聚合反应

对不同Mo含量的Mo／HZSM－5催化剂的结构进行了表征，并对这些催化剂的甲烷非氧气氛下的转化反应进行了考察．催化剂的BET比表面积及酸性随Mo含量的增加而降低，当Mo含量大于5％时，Mo对ZSM－5分子筛的晶型有影响，并出现MoO3物相．甲烷在700℃时可高选择性地生成苯和乙烯，最佳Mo含量大约为2％．纯的MoO3或HZSM－5上该反应几乎不进行，因此，可能是分散的钼氧离子和分子筛的酸中心是甲烷转化的活性中心，只有二者的协同作用才能促进甲烷的转化．反应后催化剂中的钼物种被还原了．催化剂上的积炭可能是催化剂失活的主要原因之一，烧炭后催化剂活性基本恢复．     

Molecular and crystal structures of 5,7-dichloro-4-nitro-2,1,3-benzoxadiazole and products of its reactions with secondary amines

The molecular and crystal structures of 5,7-dichloro-4-nitro-2,1,3-benzoxadiazole and products of its reactions with hexamethyleneimine and dimethylamine were established by X-ray diffraction analysis. The molecular structures and the systems of hydrogen bonds in the crystals of these compounds are discussed.     

PEO-LiClO_4-ZSM5 composite polymer electrolyte (IV): Polarized optical microscopy study

All solid-state lithium polymer batteries may be one of the best choices for the future electrochemical power source, characterized by high energy densities, good cyclability, reliability and safety[1,2]. Owing to its potential capability to replace the t…     

手性高效液相色谱法测定1—（6‘—甲氧基萘）乙醇不对称氢酯基化反应

在自制的硅基纤维素－三（３，５－二甲基苯基氨基甲酸酯）高效液相色谱手性固定相上（ＨＰＬＣ－ＣＳＰ），优化了１－（６＇－甲氧基萘）乙醇氢酯基化反应产物－萘普生甲酯手性分离的条件，测定了相应的一系列不对称氢酯基化反应产物的对映体过剩值（ｅ．ｅ．值）。结果表明，在ＣＤＭＰＣ－ＣＳＰ手性柱上用ＨＰＬＣ测定此类不对称催化反应的光学产率，评价催化剂体系的手性选择是一种非常理想的方法。     

5-Br-PADCAP分光光度法测定血清锌

为建立快速、简便、灵敏的分光光度法测定血清锌 ,在表面活性剂TritonX -1 0 0存在下 ,用 2 -(5 -溴 -2 -吡啶偶氮 ) -5 -[N ,N -二羧基甲基 ]苯酚 (5 -Br-PADCAP)作显色剂 ,不去蛋白分光光度法测定血清锌。结果表明 ,锌络合物最大吸收波长为 5 5 7nm ,线性范围 0～ 5 0 0μmol L ,摩尔吸光系数为 1 1 2× 1 0 5L·mol-1·cm-1。回收率为 99 9% ,批内变异系数 (CV)为2 1 % ,批间变异系数为 2 9% ,与原子吸收分光光度法 (x)比较具有良好的相关性 ,y =1 0 1 0x-0 1 5 4,r=0 991 8,P >0 0 5。可见本法测定血清锌不必去蛋白、用血量少、方法简便、灵敏可靠 ,适合临床应用     

网胰藻Hydroclathrus clathratus的化学成分研究

报道从中国南海网胰藻Hydroclathrus clathratus中分离得到3个单体化合物,经过MS,IR,1HNMR,13CNMR(DEPT),HMQC和HMBC等波谱技术鉴定为:(6R,7aS)-6-羟基-4,4,7a-三甲基-2,4,5,6,7,7a-六氢苯并呋喃-2-酮(1),1-(2-脱氧-β-D-呋喃核糖)-5-甲基-1,2,3,4-四氢嘧啶-2,4-二酮(2),尿嘧啶(3),并通过X射线单晶衍射实验确定化合物1的立体结构,其中化合物1是首次从自然界中分离得到.     

Carbon-bromine cleavage by dimethyl sulfoxide: the key step of C(5) functionalization of push-pull 2-alkylidene-4-oxothiazolidine vinyl bromides

Push-pull 2-alkylidene-4-oxothiazolidine vinyl bromides undergo efficient C(5) functionalization through DMSO-assisted carbon-bromine cleavage, followed by a bromine transfer-substitution (or elimination) sequence. A mechanism for this novel transformation is proposed.     

1，2，4－三嗪类化合物的研究（ⅩⅫ）──咪唑并－（5，4－e）－1，2，4－三嗪衍生物的合成

１，２，４－三嗪类化合物的研究（ⅩⅫ）──咪唑并－（５，４－ｅ）－１，２，４－三嗪衍生物的合成沙耀武，蔡孟深（北京医科大学药学院，北京，１０００８３）关键词乙二脒腙，原甲酸三乙酯，１，２，４－三嗪，咪唑并－（５，４－ｅ）－１，２，４－三嗪天然碱基拮抗...