Synthetic and biological studies on a cyclopolypeptide of plant origin

Objective: A natural cyclic peptide previously isolated from Citrus medica was synthesized by coupling oftetrapep-tide units Boc-Leu-Pro-Trp-Leu-Ome and Boc-Ile-Ala-Ala-Gly-Ome after proper deprotection at carboxyl and amino terminals followed by cyclization of linear octapeptide segment.Methods: Solution phase technique was adopted for the synthesis of cyclooctapeptide--sarcodactylamide.Required tetrapeptide units were prepared by coupling of Boc-protected dipeptides viz.Boc-Leu-Pro-OH and Boc-Ile-Ala-OH with respective dipeptide methyl esters Trp-Leu-Ome and Ala-Gly-Ome.Cyclization of linear octapeptide unit was done by p-nitrophenyl ester method.The structure of synthesized cyclopolypeptide was elucidated by FTIR,1H NMR,13C NMR,FABMS spectral data and elemental analysis.The newly synthesized peptide was evaluated for dif-ferent pharmacological activities including antimicrobial,anthelmintic and cytotoxic activities.Results: Synthesis of sarcodac-tylamide was accomplished with >78% yield utilizing dicyclohexylcarbodiimide (DCC) as coupling agent.Newly synthesized peptide possessed potent cytotoxic activity against Dalton's lymphoma ascites (DLA) and Ehrlich's ascites carcinoma (EAC) cell lines,in addition to moderate anthelmintic activity against earthworms Megascoplex konkanensis,Pontoscotex corethruses and Eudrilus sp.Moreover,cyclopolypeptide displayed good antimicrobial activity against pathogenic fungi Candida albicans and Gram-negative bacteria Pseudomonas aeruginosa,in comparison to standard drugs griseofulvin and ciprofloxacin.Conclusion: Solution phase technique employing DCC and triethylamine (TEA) as base proved to be effective for the synthesis of natural cyclooctapeptide.N-methyl morpholine (NMM) was found to be a better base for the cyclization of linear octapeptide unit in comparison to TEA and pyridine.     

双苯并咪唑烷基胺类化合物的合成

本报道二乙醇胺与1-溴代烷反应，与亚硫酰氯反应，再与2-苯并咪唑硫醇钾合成N，N-双（？-苯并咪唑-2-硫-乙基）取代胺桥联化合物。这些化合物增色被1HNMR、IR和元素分析证实。     

例谈答题思路的形象化概括

在近几年各地中考题中,以验证金属活动性顺序、判断复分解反应能否发生、不用其他试剂鉴别多种物质、比较化学反应前后溶液质量的大小为主要知识点的试题,是考查酸碱盐知识的常见题型,也是考查的重点.在解题时,如能针对答题的思路进行形象化概括,将有助于答题思路(要点)在我们头脑中打下较深的烙印,也有助于快速而准确地解答相关问题.     

无机洗涤助剂的进展

介绍了国内外洗涤助剂的发展状况，传统洗涤助剂磷酸盐被限制，沸石类助剂有局限，层状硅酸钠以优良的洗涤性能，环保无污染的特点，成为洗涤工业的新宠。     

二碘化钐引起的分子内还原偶联反应

本文综述了二碘化钐引起的分子内还原偶联反应,包括分子内酮一烯还原偶联、酮一炔还原偶联、频哪醇偶联和其它有关还原偶联反应。     

层状反铁磁体低温性质的理论计算

用自旋波理论研究了层内是反铁磁性耦合的反铁磁体的低温性质,找到了零温及有限温区的子晶格磁化强度和内能与层间耦合间的变化关系,并给出了有限温区内磁比热和平行磁化率与层间耦合之间的变化关系.     

水杨酸铁的流变相合成和红外光谱

用流变相反应法合成了水杨酸铁配合物，对样品在4000—400cm^-1。范围内的主要红外光谱吸收峰进行了归属，通过元素分析、TG和IR确定该配合物的组成为Fe(HSal)3．3H2O(HSal=O-OHC6H4CO2)。     

离子的极化作用及对化合物性质的影响

本文介绍了离子的极化作用，离子极化作用和变形性的某些规律，离子极化对化舍物性质的影响，如溶解性，热稳定性，导电率和金属性等。     

提高催化剂活性的几个途径

近年来关于催化剂活性研究认为,中心浓度[C*]和聚合增长速度常数Kp,都能使活性增加.但通过实验验证,中心浓度[C*]的活性增加率较Kp明显.同时,依据这一认识,从主催化剂、载体催化剂、助催化剂及第三组分等方面,进一步探讨和验证了提高催化剂活性的途径.     

面对"3+综合"调整复习策略--以《卤素》为例初探元素化合物复习思路

新一轮高考改革中备受关注的文理“综合科目”终于于2000年7月在江苏、浙江等省揭下了神秘的“面纱”。“理科综合”所展现的“突出基础、重视能力、体现综合”的特点，无疑对原有的教学观念、教学方式及教学策略带来了很大的冲击。面对这一现状，在高三复习中对复习策略作相应的调整，该是每一位化学教师首先应该考虑的问题。