贝壳杉烷型二萜合成进展

贝壳杉烷型二萜,特别是对映-贝壳杉烷型二萜是萜类天然产物家族中的主要组成部分.这类分子通常表现出抗菌、抗肿瘤、抗疟、抗病毒等多种重要生物活性.在分子结构上,这类四环二萜分子可以通过分子内氧化反应,切断反应以及重排反应,展现出复杂多样性.因此,对这类分子的全合成研究始终是国内外合成化学家的重点研究方向.根据这类分子的不同结构类型,分类阐述了近期国内外学者对此类分子的全合成研究.     

Maoecrystal P的全合成研究——张力双环合成子的高效应用

正对映-贝壳杉烷(ent-Kaurane)二萜是一大类具有多种重要生物活性的天然产物,50年来一直受到合成化学家的关注,一些国内外著名有机合成课题组如Corey、Ireland、Mori、Baran、Reisman、洪然、马大为、丁寒峰等均完成了该家族分子中不同成员的全合成.作为对映-贝壳杉烷中的一员,Maoecrystal P由昆明植物所孙汉董课题组分离、鉴定,并展现了对多个肿瘤细胞系良好的抑制活性.然而其氧化态高、结构复杂,全合成工作仍未见报道.北京大学化     

四类C_(20)-二萜生物碱的仿生合成

正二萜生物碱是一类具有多桥环骨架和特殊取代模式的天然产物,是萜类生物碱中最大的一个家族.由于其复杂多样化的结构和显著的生理活性,二萜生物碱的化学合成工作受到了世界各地研究小组的广泛关注.近日,四川大学华西药学院秦勇教授、刘小宇副研究员及其合作者依据二萜生物碱的生源合成假说,成功地通过仿生的方式合成     

ent-贝壳杉烷型二萜化合物的细胞毒活性研究进展

详细地概述了各类天然与合成的ent-贝壳杉烷二萜化合物的细胞毒活性研究进展, 总结和讨论了这类化合物的构效关系、作用机制以及对多种人癌细胞系的选择性, 评述了这类化合物作为抗肿瘤药物的开发潜力, 提出了目前存在的问题与不足, 并对其发展前景和研究方向做出了预测和展望.     

肉芝软珊瑚属中二聚西松烷型二萜化合物的化学和生物活性研究进展

二聚西松烷型二萜(biscembranoid)是一类骨架新颖、结构复杂、罕见的海洋天然产物,主要存在于肉芝软珊瑚属珊瑚生物中.这类化合物多具有显著的生物活性,尤其表现为抗炎、抗肿瘤等.对近年来报道的肉芝软珊瑚属中的二聚西松烷型二萜化合物的化学及生物活性进行综述,并对其药用前景作出展望.     

Wallichanol类天然产物ABC环系合成研究

Wallichanol是一类具有独特桥环结构的二萜天然产物.以2-甲基-1,3-环己二酮作为起始原料,通过高立体选择性的Diels-Alder反应和金催化的炔烃碳环化反应构建Wallichanol的ABC三环核心骨架,共七步路线,总收率为42%.该合成工作为Wallichanol类天然产物全合成奠定了研究基础.     

基于分子内的仿生Diels-Alder反应构建Elansolid A1/A2的四氢茚烷核心结构(英文)

Elansolid A1/A2是从滑行细菌Chitinophaga sanctii中分离出来的次级代谢产物,具有抗菌活性.迄今为止,该天然产物的全合成尚未被报道,主要由于其化学结构复杂,包含反式四氢茚烷单元、(Z)-(E)-(Z)共轭三烯及19元大环内酯结构.在此研究中,两种含氧官能团的底物被合成出来并考察了这两种底物在手性磷酸催化下进行分子内的仿生Diels-Alder反应(IMDA),成功地构建了Elansolid A1/A2中的反式四氢茚烷核心骨架,且该Diels-Alder反应的非对映选择性提高到了1.8∶1以及减少了合成步骤.     

多环型Xanthone类天然产物的合成研究进展

多环型xanthone类天然产物是一类具有高度氧化态和六环骨架结构的天然产物.目前分离得到的此类化合物主要来源于放线菌.由于这类化合物具有结构特独、广泛的抗细菌活性、一定程度的抗真菌活性以及良好的抗肿瘤活性,吸引了大量有机合成和药物化学等领域学者的关注.近十年来,相关的生物和化学合成以及药物化学研究报道明显增多,主要总结了多环型xanthone类天然产物的合成研究进展.     

中国海洋天然产物合成研究新进展

海洋天然产物合成研究是海洋天然有机化学最活跃的研究领域之一。本文综述中国海洋天然产物合成研究的最新进展,包括海洋环肽、西松烷(烯)和西松烷型二萜内酯、喹啉酮衍生物和三丙酮胺以及柳珊瑚酸类似物等。     

光促进的山道年重排反应在复杂萜类天然产物全合成中的应用

萜类化合物在自然界中广泛存在,其中倍半萜内酯广泛存在于各种药用植物中,是许多传统中草药的主要活性成分,然而这类化合物的化学全合成却极具挑战性.山道年是一种廉价的可再生资源,且光促进的山道年重排反应是一种构建愈创木内酯骨架的高效方法,在萜类天然产物合成中得到广泛应用.就光促进的山道年重排在复杂萜类天然产物的合成工作进行简单的概述,主要包括倍半萜内酯及其寡聚物全合成以及个别二萜天然产物的骨架合成研究.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.