An Efficient Way for Glycosylation of Spirostanol

Using thioglycosides as donors, trimethylsilyl trifluoromethanesulfonate (TMSOTf) and N-iodosuccinimide(NIS) as promoter, a modified procedure for the glycosylation of spirostanol was developed. A series of saponins were synthesized in mild condition with excellent yields.     

质谱在天然产物研究中的应用举例

质谱对天然产物化学具有重大的影响。我们在化学结构的研究中曾广泛应用质谱,但由于专业的限制(有机化学),所涉及的均为常用的质谱技术。所举各例,有不少来自其他的有协作关系的研究组。     

井冈山自然保护区爬行动物初步调查

<正> 一地理概况井冈山自然保护区位于江西省西部,罗霄山脉中段。东接太和,东南连遂川,西接宁冈和湖南酃县,西北连永新,介于东径113°59′—114°23′。北纬26°27′—26°49′之间。地势西高东低,境内群山环抱,山体蜿蜒曲折,多呈西南向东北走向,形成山间峡谷和山间盆地。河溪     

微量脉冲进样-导数火焰原子吸收光谱法测定调味品中锌

将微量脉冲进样技术和导数火焰原子吸收光谱法结合 ,建立了测定调味品中锌含量的新方法。探讨了微量进样体积和导数仪档位等影响因素。样品经离心、稀释后直接测定 ,该方法的灵敏度和检出限分别为 0 0 0 4和 0 0 13μg·mL-1,相对标准偏差为 3 0 %～ 4 4 % ,回收率 93 3%～ 113 3%。该方法准确和快速 ,结果令人满意。     

用雅可比-傅里叶矩进行图像描述

提出了雅可比—傅里叶矩,它是用雅可比多项式作为径向函数,用傅里叶因子作为角向函数构造而成的,是广义正交傅里叶—梅林矩。经过归一化处理后的雅克比—傅立叶矩具有平移、尺度、旋转、灰度多畸不变性。从归一化图像重建误差、噪声灵敏度等方面对雅可比—傅里叶矩的图像描述能力进行了研究,结果显示雅可比—傅里叶矩在各种参量选择的情况下,具有良好的图像描述和抗噪声能力,是一个优良的图像特征。以前的研究多为单纯构建某一个函数,而现在将其扩展为构建一个函数族,开阔了矩描述量的研究视野。     

十八种清热解毒中草药中微量元素的测定

采用原子吸收分光光度法测定了十八种清热解毒中草药中人体必需微量元素含量。结果表明,这些中草药中含有丰富的人体必需微量元素。本方法具有操作简便、快速和准确度高等优点。     

Evaluation of lipid peroxidation inhibition and free radical scavenging abilities of 5,6,7-trimethoxy dihydroflavonols

Four naturally rare 5,6,7-trimethoxy-2,3-cis-dihydroflavonols(3-6) and two 5,6,7-trimethoxy-2,3-trans-dihydroflavonols(7-8) were designed and synthesized.Their antioxidative properties were evaluated by way of examining their scavenging capacities towards DPPH and O_2~(·-) free radicals,as well as by measuring their inhibitory ability against LPO.Both the 2,3-trans and the 2,3- cis conformers exhibited certain quenching abilities to DPPH and O_2~(·-) radicals,while most of the synthetic dihydroflavonols ...     

A new method for introduction ω-side chain of prostanoid using Barton radical reaction

A new method for introductionω-/side chain of prostanoid was described in this note.Starting from acid chloride(3),via Barton radical reaction,a transα,β-unsaturated ketone sython was introduced.     

Two new triterpenes from Duchesnea indica

Two new triterpenes,2α,3β-dihydroxyurs-12-en-18,19-epoxy-28-oic acid(1)and 18,19-seco,2α,3α-dihydroxyl-19-oxo-urs-11, 13(18)-dien-28-oic acid(2)were isolated from the herbaceous part of Duchesnea indica.Their structures were elucidated by spectroscopic analysis,including 2D NMR technique.The isolated compounds exhibited moderate cytotoxic activities against HeLa and L929 cell lines.     

Two new ent-kaurane diteroenoids from Isodon excisoides

Two new ent-kaurane diterpenoids taihangexcisoidesin A and B(1 and 2),were isolated from the EtOAc extract of the leaves of Isodon excisoides.Their structures were determined on the basis of spectroscopic methods.