青蒿素转化成异氢化青蒿酸及有关反应

本文报道从青蒿素经六步反应转化成异氢化青蒿酸。青蒿素经酸处理得失碳倍半萜内酯3,3经硷水解再酯化生成α,β-不饱和酮酯5,然后由Wittig反应得共轭双烯酯6,用RaneyNi(W_2)催化氢化生成异氢化青蒿酸酯7,最后经硷水解得到异氢化青蒿酸8。     

芫花有效成分的研究——Ⅲ.新的二萜原酸酯芫花酯丙的分离与结构

瑞香科植物芫花的花以乙醇提取,除分得芫花酯甲、酯乙外,尚分得新的二萜原酸酯芫花酯丙。根据光谱和化学反应确定其结构为1。从该植物根的石油醚提取物中分得已知二萜原酸酯-12-苯甲酰氧基瑞香毒素(2)。1和2均对皮肤有刺激作用,1对孕猴具有引产作用。     

Theory of relaxation spectra of polymer networks with interchain friction and long-range hydrodynamic interactions

The dynamic network model taken into account the friction relative to incompressible effective viscous medium (EVM), the hydrodynamic interactions of a network with the EVM, and the interchain friction is considered. Two collective network relaxation spectra (RS) arise. The first RS corresponds to the network motion relative to immobile EVM, the EVM does not take part in this motion. The second RS includes the combined viscous motion of the network and EVM because of long-range hydrodynamic interactions. This RS is finite and narrow for infinitely large network. The symmetry of this motion is in concordance with that of incompressible EVM. The existence of interchain friction leads to the narrowing of both types of relaxation spectra.     

二分图中关于Enomoto问题的结果

设k,n1和n2是3个正整数,G=（V1,V2;E）是一个二分图,使得｜V1｜=n1,｜V2｜=n2,其中n1≥2k＋1,n2≥2k＋1并且n1-n2≤1．如果对任意不相邻的x∈V1和y∈V2,都有d（x）＋d（y）≥2k＋2,则G包含k个相互独立的圈．以上结果部分地回答了Enomoto提出的关于二分图有独立圈的问题．     

利用四氯乙烷胺化反应合成联氢化嘧啶衍生物的研究

利用均四氯乙及二氯甲烷的胺化反应,合成了联氢化嘧啶衍生物1～5,4a,8b-反-4,5,8a,9a-四氮杂全氢芴(6)和8b,8c-顺-3a,4a,7a,8a-四氮杂环戊并全氢芴(7)。化合物(6)和(7)的顺反异构体在酸催化下开环,异构生成较稳定的6b和7a。     

NEAR-UV ACTIVATION OF ENZYMATIC CONVERSION OF 5-HYDROXYTRYPTOPHAN TO SEROTONIN

Near-UV (337 nm) photoactivation of the 5-hydroxytryptophan decarboxylation reaction producing serotonin has been observed. The photoactivation effect was investigated as a function of fluence rate and fluence, and pH. Photoactivation of decarboxylase activity was found to occur at nearly neutral pH values (low activity of the enzyme in the dark). The findings indicate that the effect of light is similar to a pH shift toward the acid region, which causes the enzyme conversion from the inactive to active form. Pyridoxal phosphate, the decarboxylase cofactor, in the form of an adduct absorbing at 330-340 nm, is suggested as a candidate for the role of the photoactive chromophore of decarboxylase.     

Transition Metal Ion-binding Properties of a 14-Membered N2O2S2- Macrobicyclic Ligand

The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N₂O₂S₂-macrobicycle. Metal picrates such as Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺,Cu²⁺ and Cd²⁺ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb²⁺ only among the other metals. The extraction constant (log K _ex) was determined to be 13.8 for Pb²⁺ complex.     

Carbohydrate Structure Database (CSDB): new features

Russian Chemical Bulletin - Carbohydrate Structure Database (CSDB) is a regularly updated database containing structural, taxonomic, bibliographic, NMR spectroscopic, and other information on...