Xyloketal G,a Novel Metabolite from the Mangrove Fungus <Emphasis Type="Italic">Xylaria sp.</Emphasis> 2508

A novel metabolite 1, named xyloketal G, was isolated from cultures of marine derived mangrove fungus Xylaria sp. 2508. Its structure was elucidated by analysis of spectroscopic data.__________Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 22–23, January–February, 2005.     

Ar n HF van der Waals clusters revisited. I. New low-energy isomeric structures for n=6-13

New low-lying isomeric structures of Ar(n)HF clusters are reported for n=6-13. They were determined using simulated annealing and evolutionary programming, for pairwise additive intermolecular potential energy surfaces. New global minima were found for the clusters with n=7, 10, 11. The new lowest-energy structure of Ar(7)HF and several new local minima for n=6, 7 clusters have the HF bound on a threefold surface site, consistent with the recent spectroscopic data for Ar(n)HF clusters in helium nanodroplets. A new type of low-energy local minima were determined for n=9-13 clusters.     

几种杂多阴离子柱撑水滑石的合成与吸附行为

柱撑水滑石类层柱状阴离子粘土是一类新型层柱材料，由于其二维孔道结构的可调变性及潜在的择形催化性能，已引起人们的重视[1-3]．迄今，人们已合成了包括无机和有机阴离子，同多和杂多阴离子（Polyoxometalates，简称POMs）以及配合物阴离子在内的多种柱撑水滑石，其中同多和     

铝（Ⅲ）—桑色素—含氧有机溶剂荧光体系的研究

本文系统研究了醇、酮等7种含氧有机溶剂对铝-桑色素络合物荧光反应的溶剂化效应。研究发现,上述有机溶剂对荧光体系均有增敏作用,以乙醇的效果最佳,使络合物的荧光强度增加6倍多。据此,本文建立了测定微量铝的高灵敏度荧光分析方法,线性范围为0～1.0μg/10ml,检测限为1.6×10~(-9)g/ml。用所建立的方法对化学试剂中的微量杂质铝进行了测定,结果令人满意。并对有机溶剂化效应的机理作了探讨。     

D-葡萄糖D-果糖与硼的有机物形成配合物的稳定性研究

葡萄糖异构酶加速葡萄糖与果糖的平衡,平衡时果糖含量为42％左右,体系中加入一些硼酸盐,果糖的含量提高到80％左右,究其原因可能是由于葡萄糖和果糖与硼酸盐形成不同稳定性的配合物。虽然Roy,Conner,Daris,Belcher,Lorand等都已报导了这些配合物的稳定常数,概括结果分歧较大。Belcher曾首次报导了硼酸与D-果糖的配位数为     

Preparation of [5,6]- and [6,6]-oxahomofullerene derivatives and their interconversion by Lewis acid assisted reactions of fullerene mixed peroxides

[60]Fullerene mixed peroxides C60(O)(OOtBu)4 exhibit chemo- and regioselective reactions under mild conditions. The epoxy moiety is opened by ferric chloride to form vicinal hydroxy chloride C60Cl(OH)(OOtBu)4. BF3 is also effective in opening the epoxy moiety. The O-O bond of the fullerene mixed peroxide is cleaved by aluminum chloride to form both [5,6]- and [6,6]-fullerene hemiketals (oxohomo[60]fullerenes). A Hock-type rearrangement is proposed for the formation of the hemiketals, in which a fullerene C-C bond is cleaved. Lewis acids and/or visible light can initiate isomerization of the hemiketal isomers. Single-crystal X-ray analysis and theoretical calculations confirmed the results.     

有机元素微量分析标准物质——茴香酸的研制

茴香酸的分子式为C_8H_8O_3,碳含量63.15%、氢含量5.30%、氧含量31.55%、甲氧基含量20.40%。该标样与日本元素分析恳谈会委员会、英国化学协会微量化学委员会所公布的微量化学标样之一——香草醛一样,都具有相同的碳、氢、氧和甲氧基含量,美国国家标准局(NBS)发行SRM142茴香酸作为微量分析中甲氧基的分析标样。     

A mesoporous non-precious metal boride system: synthesis of mesoporous cobalt boride by strictly controlled chemical reduction

Generating high surface area mesoporous transition metal boride is interesting because the incorporation of boron atoms generates lattice distortions that lead to the formation of amorphous metal boride with unique properties in catalysis. Here we report the first synthesis of mesoporous cobalt boron amorphous alloy colloidal particles using a soft template-directed assembly approach. Dual reducing agents are used to precisely control the chemical reduction process of mesoporous cobalt boron nanospheres. The Earth-abundance of cobalt boride combined with the high surface area and mesoporous nanoarchitecture enables solar-energy efficient photothermal conversion of CO₂ into CO compared to non-porous cobalt boron alloys and commercial cobalt catalysts.

Generating high surface area mesoporous transition metal boride is challenging but interesting because incorporation of boron atoms can generate lattice distortion to form amorphous metal boride which has unique properties in catalysis.     

Evaluating and clustering retrosynthesis pathways with learned strategy

With recent advances in the computer-aided synthesis planning (CASP) powered by data science and machine learning, modern CASP programs can rapidly identify thousands of potential pathways for a given target molecule. However, the lack of a holistic pathway evaluation mechanism makes it challenging to systematically prioritize strategic pathways except for using some simple heuristics. Herein, we introduce a data-driven approach to evaluate the relative strategic levels of retrosynthesis pathways using a dynamic tree-structured long short-term memory (tree-LSTM) model. We first curated a retrosynthesis pathway database, containing 238k patent-extracted pathways along with ∼55 M artificial pathways generated from an open-source CASP program, ASKCOS. The tree-LSTM model was trained to differentiate patent-extracted and artificial pathways with the same target molecule in order to learn the strategic relationship among single-step reactions within the patent-extracted pathways. The model achieved a top-1 ranking accuracy of 79.1% to recognize patent-extracted pathways. In addition, the trained tree-LSTM model learned to encode pathway-level information into a representative latent vector, which can facilitate clustering similar pathways to help illustrate strategically diverse pathways generated from CASP programs.

Tree-structured long short-term memory neural model learns to understand the retrosynthesis design strategies from patent-extracted retrosynthetic pathway data.