inium (EMP+) ions in aqueoussolution at room temperature by eaq−and · CO2− was investigated in a pulseradiolysisstudy (irradiation with 10 ns pulses of 45 MeV electrons). For comparison, experiments with 1-methylpyridinium (MP+) and unsubstituted pyridinium (PH+) ions were carried out. With MP+ and PH+ the spectra of pyridinyl radicals were observed at the end of the pulse. In the case of EMP+ the
Studies on chemical carcinogens and mutagens. XXXII. Chemoselectivity of alkylating agents toward pyridine in aqueous media - A simple procedure for evaluation of Swain-Scott's substrate constants.
作者:SHINICHI NINOMIYA、YUTAKA KAWAZOE
DOI:10.1248/cpb.33.5207
日期:——
A simple method for the evaluation of the chemoselectivit of alkylating agents toward pyridine in aqueous media is proposed. The analytical method involves the evaluation of the relative rate of quaternization of pyridine with respect to the rate of hydrolysis in aqueous buffer (pH 6.0), i.e., the evaluation of chemoselectivity toward pyridine in competitive nucleophilic attacks of a given alkylating agent on the nitrogen of pyridine versus the oxygen functions in phosphate buffer containing a large excess of pyridine. The term Spy is tentatively defined as log (N/(1-N)) × [H2O]/[py]}, where N is the molar fraction consumed for pyridine quaternization after the complete consumption of the given alkylating agent, and [H2O] and [py] are the concentrations of water and pyridine, respectively. Spy correlated linearly with the substrate constant (s) defined by Swain and Scott : s=0.163Spy+0.209 (r=0.995, n=8) at 37°C in 4% acetone-containing 1/15 M phosphate buffer (pH 6.0). The dependences of the chemoselectivity on the reaction temperature and the acetone content of the medium are briefly discussed.
本文提出了一种评估烷化剂在水介质中对吡啶的化学选择性的简单方法。该分析方法包括评估吡啶在水性缓冲液(pH 值为 6.0)中的相对季铵化速率和水解速率,即评估在含有大量过量吡啶的磷酸盐缓冲液中,给定烷化剂对吡啶的氮功能和氧功能进行竞争性亲核攻击时对吡啶的化学选择性。Spy 一词暂时定义为 log (N/(1-N))×[H2O]/[py]},其中 N 是在完全消耗给定的烷化剂后吡啶季铵化所消耗的摩尔分数,[H2O]和[py]分别是水和吡啶的浓度。在 37°C 含 4% 丙酮的 1/15 M 磷酸盐缓冲液(pH 值为 6.0)中,Spy 与 Swain 和 Scott 定义的底物常数(s)呈线性相关:s=0.163Spy+0.209(r=0.995,n=8)。本文简要讨论了化学选择性与反应温度和介质中丙酮含量的关系。
An inverse reactivity-selectivity relationship. Kinetic nitrogen isotope effects on methyl transfer to pyridines
作者:Joseph L. Kurz、Moheb M. Seif El-Nasr
DOI:10.1021/ja00385a062
日期:1982.10
becomes more reactive. These changes in K/sub 14//K/sub 15/ demonstrate increasing selectivity for /sup 15/N in preference to /sup 14/N as reactivity increases and thus are in violation of the reactivity-selectivity principle. However, these observed changes in K/sub 14//K/sub 15/ are consistent with a very recent prediction that such ''anti-Hammond'' effects should result from changes in quantum mechanical
Nouvelle synthese simple de nucleoside phosphorothiolate
作者:U. Asseline、N.T. Thuong
DOI:10.1016/0040-4039(81)80012-3
日期:1981.1
The O,S-dimethylphosphorochloridate reacts with 5′-O-monomethoxytritylthymidine in pyridine giving nucleoside-3′-thiolophosphodiester in high yields; in acetonitrile and in the presence of 1-methylimidazole, this reaction leads to the nucleoside-3′-phosphotriester without formation of diester . From the latter, the Tp and TpT have been prepared.
METHODS AND COMPOSITIONS FOR DIABETES TREATMENT AND PREVENTION
申请人:Hofmann Thomas
公开号:US20110288014A1
公开(公告)日:2011-11-24
The present invention relates to methods and compositions for preventing or treating diabetes. The invention in particular discloses compounds according to formula (I) for use in the prevention and treatment of type II or I diabetes.