短足软珊瑚Cladiella latissima中二萜化合物研究

软珊瑚是热带和亚热带海洋中常见的海洋腔肠动物,对其化学成分及生理活性研究发现软珊瑚中主要含有结构新颖的倍半萜、二萜和多羟基甾醇等化合物,个别软珊瑚中含有自然界罕见的双大环四萜类化合物.本文报道对采自广西北海的短足软珊瑚(Cladiella latissima)中的二萜化合物的研究.     

南海短足软珊瑚Cladiella sp.中两个新孕甾醇苷的分离

从短足软珊瑚Cladiella sp．中,分离得到3个甾类化合物：孕甾-5,20-二烯-3β-醇-3-O-α-L-吡喃岩藻糖苷(1)、孕甾-5,20-二烯-3β-醇-3-O-β-D-吡喃木糖苷(2)和(22E,24R)-麦角甾-7,22-二烯-3β,5α,6β-三醇(3),其中1和2为新化合物．孕甾醇苷具有抗早孕和抑制肿瘤细胞生长活性．     

柔软肉芝软珊瑚中的新二萜内酯

肉芝软珊瑚Sarcophytum是珊瑚纲,八放珊瑚亚纲,软珊瑚目中的一个属,软珊瑚肉质柔软而不被海洋中的动物所吞食,这被认为是与其次生代谢产物中含有能驱赶其它生物的化学防御物质有关,从而引起了化学家和药物学家的重视^[1,2],例如从乳白肉芝软珊瑚Sarcophytum glaucum和第氏肉芝办珊瑚Sarcophyton decasyi中均分离得到细胞毒活性相当强的二萜内脂Sarcophine^[3-5],Bernstein^[3]认为这类物质可能是软珊瑚的化学防御物质之一,最近我们在研究柔软肉芝软珊瑚Sarcophyton molle Tix.Dur.的次生代谢产物过程中,分离到两个在生源上与Sarcophine有密切关系的二萜内酯 Sarcophinone(1)^[6,7]和iso-Sarcophinone(2),其中2是新化合物。体外的生理活性试验显示,化合物1和2对艾氏腹水瘤细胞和水鼠S180肿瘤细胞均有显著抑制作用,本文报道了Sarcophinone(1)和iso-Sarcophinone(2)的分离和结构测定。     

肉芝软珊瑚Sarcophyton crassocaule中新的多羟基甾醇的分离

报道了从三亚海域的一种肉芝软珊瑚Sarcophyton crassocaule Mosre中分离得到2个多羟基甾醇1和2. 通过波谱分析等方法测定了它们的化学结构, 化合物1为新化合物, 命名为Sarcrasterol. 化合物2为已知物[24ξ-methyl-colestane-3β,5β,6α,25-tetrol], 但其C24构型未确定, 通过X射线单晶衍射分析测定了其相对构型为24S.     

两种新的多羟基甾醇化合物分离与结构鉴定

采用现代分离手段,从采自中国南海硇洲岛的软珊瑚Chromonephthea sp.中分离纯化得到两种甾醇化合物,经过MS,IR,1H NMR,13C NMR(DEPT),HSQC,HMBC和NOE等光谱技术鉴定它们的结构为:24-甲基胆甾-5-烯-3β,12β,16β,20-四醇(1)和24-乙基胆甾-5-烯-3β,12β,16β,20-四醇(2),这两个化合物均为新化合物.肿瘤活性实验表明两种甾醇化合物显示微弱的细胞毒性.     

从中国南海软珊瑚中分离的环氧西松烯天然产物的结构更正

(- ) - 7,8- Epoxycembrene- C[( - ) - 7,8- ECC,1 ]是 Bowden等 [1] 于 1 980年首次从澳大利亚软珊瑚Sarcophyton crassocaule中分离得到的新的环氧西松烯 .其化学结构经光谱数据证实为 ( 1 E,3E,1 1 E) -1 -异丙基 - 4,8,1 2 -三甲基 - 7,8-环氧 - 1 ,3,1 1 -十四碳环三烯 ,但 C- 7,C- 8位环氧的立体化学未被确定 . Shin等 [2 ] 也从未鉴定属名的加勒比海域的软珊瑚 Eunicea sp.中分离得到过该天然产物 . 1 997年 ,饶志刚等 [3] 报道了从中国南海肉芝软珊瑚 ( Sarcophyton molle)中分离得到一环氧西松烯天然产物 ,确定其结构为天然…     

两个新的海洋倍半萜

从稠密短指软珊瑚Sinularia conferta 中分离得1个新倍半萜confertol(1)。 从荑柔软珊瑚Nephthea albida分离得1个新倍半萜nephalbidol(2)和1个已知的多 羟基甾醇nephalsterol A(3)，应用波谱方法测定了的化学结构和相对构型。     

19—羟基甾醇Nephalsterol—B的结构研究

前文报道了从西沙群岛采集的软珊瑚Nephthea albida和南沙群岛采集的软珊瑚Nephthea tixiexae verseveldt分离到一种罕见的含19-羟基的四羟基甾醇Nephalsterol A(1).本文报道从N.tixiexae verseveldt分离到的另一种19-羟基甾醇Nephalsterol-B的结构测定. Nephalstereol B(2)为无色针状结晶,m.p.159～161℃(乙酸乙酯);160～162℃(丙酮),[α]_D~(27)+25°(C 0.100,甲醇),2的~(13)C NMR及其DEPT谱表明分子中含有4个CH_3,11个     

软珊瑚Sarcophyton sp.中一个新的西松烷二萜内酯的分离及结构测定

肉芝软珊瑚 Sarcophyton富含二萜 ,从这类软珊瑚生物体中已经分离出许多含十四元环结构的西Scheme 1　 Sturcture of Sarcophydiol 1松烷二萜内酯 ,例如 Sarcophinone[1] ,iso-Sarcophinone[2 ] ,Sarcophine[3,4 ] ,Sartrochine[5] 和 iso-Sarcophine[6 ,7] .这些西松烷二萜内酯均有较强的细胞毒性 .在对采自南中国海的一种肉芝软珊瑚 Sar-cophyton sp.次生代谢产物的研究过程中 ,我们分离得到一个在生源上与 iso- Sarcophine有密切关系的新西松烷二萜内酯 Sarcophydiol 1 (结构见Scheme 1 ) .本文报道其分离方法及结构测定结果 .1　…     

鹿角短指软珊瑚Sinularia Cervicornis Tix-Dur 中的一个新糖甙-Cervicoside

珊瑚属腔肠动物门 ( Clelenterata) ,海鸡冠目 ( Alcyonacea) ,是一种热带与亚热带海洋中广泛分布Scheme 1　 Structure of cervicoside(1 )的低等海洋生物 .软珊瑚的次生代谢物中含有萜类和甾体类等各类生理活性物质[1～ 5] .我们在对鹿角短指软珊瑚的次生代谢产物研究中 ,分离到一个新三糖甙 ,命名为 Cervicoside( 1 ) ,结构见 Scheme 1 .该化合物具有较强的体外抗癌活性 .1　实验部分1 .1　样品　鹿角短指软珊瑚采自海南岛三亚海域 .样品储藏于中山大学化学与化学工程学院天然有机化学研究室 ,编号为 98- SY- 3.种属由中国科学院南海…     

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.     

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.