A novel synthesis of N-protected carbazoles involving electrocyclization of in situ generated enamines

A new route for the synthesis of carbazoles has been realized through the intermediacy of 2,3-divinylindoles involving an electrocyclization followed by aromatization.     

Photochemical electrocyclization and leaving group expulsion with a naphthothiophene-2-carboxanilide linked to a chromophore

A naphthiothiophene-2-carboxanilide bearing a leaving group at the C-3 position undergoes efficient electrocyclic ring closure and leaving group expulsion upon direct photolysis. The reaction occurs in the triplet excited state and can be sensitized by thioxanthone. Thioxanthone as chromophore can also be covalently attached to amide nitrogen by a trimethylene linker, and the photoreaction is equally efficient. Quenching studies show that the triplet excitation is localized primarily on the naphthothiophene moiety, due to rapid exothermic energy transfer from the thioxanthone chromophore. Acriflavin dye is capable of sensitizing the photoreaction at 450?nm, but the quantum yield is low in this case.     

Synthesis of substituted carbazoles via electrocyclization of in situ generated enamines from 1-phenylsulfonyl-2/(3)-methyl-3/(2)-vinylindoles and DMF·DMA/DMA·DMA

Interaction of 2/(3)-methyl-3/(2)-vinylindoles and DMF·DMA/DMA·DMA at 110 °C led to the in situ generation of enamines, which on concurrent electrocyclization followed by subsequent aromatization afforded substituted carbazoles.     

A biomimetic synthesis of the indolo[3,2-j]phenanthridine alkaloid, calothrixin B

A biomimetic approach to calothrixin B via a hypothetical metabolite, 6-formylindolo[2,3-a]carbazole, is described. The construction of a suitable indolo[2,3-a]carbazole ring system was carried out using an allene-mediated electrocyclic reaction involving two [b]-bonds of indoles as the key step.     

A new total synthesis of an indolo[3,2-j]phenanthridine alkaloid calothrixin B

A new total synthesis of calothrixin B is described. The key step is an allene-mediated electrocyclic reaction involving the indole 2,3-bond for the construction of a suitable 4-oxygenated 2,3,4-trisubstituted carbazole ring system.     

胞壁酰二肽(MDP)及其类似物的合成

本文报道胞壁酰二肽(MDP)及其类似物MDP[γ-Abu]^1、MDP-Oxalys的合成。应用一些新的合成方法和一种新型高效缩合剂, 简化了合成步骤, 提高了收率。     

Synthesis and biological evaluation of tamandarin B analogues

[structure: see text]. The synthesis of two tamandarin B analogues in which the N,O-Me2Tyr5 unit was replaced by N-Me-phenylalanine (N-MePhe5) and (S)-2-(methylamino)-3-(naphthalen-2-yl)propanoic acid (N-MeNaphth5) is described. The choice of the macrocyclization site was crucial to achieve satisfactory macrolactamization. Coupling between norstatine (Nst1) and threonine (Thr6) afforded only a 15% yield, while lactamization between proline (Pro4) and the aromatic moiety could be achieved in 65% yield.     

微波辅助合成纳米复合材料Ag/ZnO-ZnS及其光催化降解若丹明B初步研究

采用微波辅助合成方法制备了具有高光催化活性的纳米复合材料Ag/ZnO-ZnS,经X-射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜配合X-射线能量色散谱仪(SEM-EDS)以及氮气吸附-脱附测定等对合成材料的结构、形貌和表面物理化学性质进行了表征。结果表明,经微波处理后的纳米复合材料Ag/ZnO-ZnS中Ag以单质形式存在,具有纤锌矿晶型结构,属介孔材料,平均孔径约为4.1nm,比表面积更大,颗粒分布更加均匀。通过模型分子若丹明B分别考察了紫外和微波辐射下Ag/ZnO-ZnS的光催化活性,结果显示,微波辅助合成的Ag/ZnO-ZnS具有更高的光催化活性,其在微波增强光催化条件下,40min内对若丹明B脱色率达99%以上,明显高于市售P25等其他体系。     

Synthesis of substituted pyrazoles via tandem cross-coupling/electrocyclization of enol triflates and diazoacetates

The synthesis of 3,4,5-trisubstituted pyrazoles via a tandem catalytic cross-coupling/electrocyclization of enol triflates and diazoacetates is presented. The initial scope of this methodology is demonstrated on a range of differentially substituted acyclic and cyclic enol triflates as well as an elaborated set of diazoacetates to provide the corresponding pyrazoles with a high degree of structural complexity.     

Synthesis of (+)-vinblastine and its analogues

A synthetic route to vinblastine and its analogues with an ethynyl group, which features a stereoselective coupling of an 11-membered key intermediate with vindoline, is described. Transformations of the alkynyl moiety including a partial reduction as well as a Sonogashira coupling furnished a variety of analogues.     

Synthesis of pyrazolo-fused heterocycles by a tandem appel's dehydration/electrocyclization methodology

The hydrazones of benzophenone, benzil, and acetophenone were allowed to react with acetoacetanilide to give azinoamides 18 , and the reaction of 18 with Appel's dehydrathon contiditons (triphenylphosphine/carbon tetra-chloride/triethylatnine) led to the corresponding azinoketimines 19 , which underwent elctrocyclic ring closure under the reaction conditions to give pyrazolo-fused heterocycles. Azinoamide 18a gave a 4,9-dihydropyazolo-[5,1-b]quinazoine 21 , while 18b yielded 2,3-dihydro-1H-imidazo[1,2-b]pyrazol-2-one 26 and 1H-imidazo[1,2-b]-pyrazole 29 . Compound 18c gave a monocyclic N-α-styryl-5-(phenylamino)pyrazole 32 .     

Total synthesis of calothrixins A and B via oxidative radical reaction of cyclohexenone with aminophenanthridinedione

Bioactive indolo[3,2-j]phenanthridine alkaloids, calothrixin B and its N-oxide derivative calothrixin A have been synthesized via an oxidative free radical reaction. Calothrixin B is generated from the commercially available 2,4,5-trimethoxybenzaldehyde in only seven steps. The key step in this synthesis is the Mn(OAc)₃ mediated oxidative free radical reaction of 9-(benzylamino)phenanthridine-7,10-dione with cyclohexenone to form 12-benzyl-12H-indolo[3,2-j]phenanthridine-7,13-dione.     

Synthesis of indole alkaloids arsindoline A,arsindoline B and their analogues in low melting mixture

Synthesis of newly isolated bis(indolyl)methane alkaloids arsindoline A, arsindoline B from a marine-derived bacterium strain CB101 and their analogues are reported using low melting l-(+)-tartaric acid–dimethyl urea mixture. The reaction is mild, non-toxic, and occurs in environmentally benign conditions. We also reported the synthesis of another alkaloid 2,2-bis(6-bromo-1H-indol-3-yl)ethanamine using low melting mixture.     

Synthesis of perfragilin A, B and some analogues

Synthesis of the cytotoxic isoquinoline quinone perfragilin A, an improved synthesis of perfragilin B and preparation of some analogues of both these compounds are described. Cytotoxicity evaluation of a number of the products is reported. The regioselectivity in Diels-Alder reactions of differently substituted benzoquinones with 2-aza-1,3-bis(t-butyldimethylsilyloxy)-1,3-butadiene is described.     

Synthesis of fluorine and iodine analogues of clorgyline and selective inhibition of monoamine oxidase A

A series of fluorine and iodine analogues of clorgyline was synthesized and evaluated for inhibitory potency and selectivity toward monoamine oxidase A (MAO-A). Among them, N-[3-(2,4-dichloro-6-iodophenoxy)propyl]-N-methyl-2-propynylami ne (3d), N-[3-(4-chloro-2-fluorophenoxy)propyl]-N-methyl-2-propynylamine (3f) and N-[3-(2-chloro-4-fluorophenoxy)propyl]-N-methyl-2-propynylamine (3g) were found to have high inhibitory potency and selectivity toward MAO-A comparable to those of clorgyline itself. Thus, they were considered for advanced development as radiofluorinated and radioiodinated ligands that may be useful for functional MAO-A studies in the living brain with positron emission tomography and single photon emission computer tomography.     

Synthesis of 8,9-disubstituted fluoranthenes by domino two-fold Heck/electrocyclization/dehydrogenation of 1,2-dibromoacenaphthylene

Fluoranthenes were prepared by domino two-fold Heck/electrocyclization/dehydrogenation reactions of 1,2-dibromoacenaphthylene.     

基于咔唑的单-/双-硫代碳酰腙衍生物的合成及Cdc25B/PTP1B抑制活性评价

合成了一系列新型的基于咔唑的单-/双-硫代碳酰腙衍生物.利用IR、1H NMR、13C NMR和元素分析对其进行了结构表征.评价了目标化合物对Cdc25B和PTP1B的抑制活性,讨论了其结构与活性的关系.实验结果显示,大部分目标化合物对Cdc25B和PTP1B表现出良好的抑制活性.其中,1,5-双[(9-戊基-3-咔唑基)亚甲基]硫代碳酰腙(4d)对Cdc25B的抑制活性最高,IC50为(0.23±0.02)μg/m L.1,5-双[(9-乙基-3-咔唑基)亚甲基]硫代碳酰腙(4a)对PTP1B的抑制活性最高, IC50为(1.00±0.16)μg/m L.对目标化合物4a和4d进行分子对接研究和密度泛函理论(DFT)计算,结果表明,目标化合物4d和4a分别进入到了Cdc25B和PTP1B酶的活性位点区域,有活性作用的主要是硫代碳酰腙和咔唑基团.     

Synthesis and biological activity of kalkitoxin and its analogues

Total syntheses of kalkitoxin, isolated from the Caribbean Lyngbya majuscula, and its analogues, 3-epi-, 7-epi-, 8-epi-, 10-epi-, 10-nor-, and 16-nor-kalkitoxin, were achieved via oxazolidinone-based diastereoselective 1,4-addition reaction of a methyl group and efficient TiCl(4)-mediated thiazoline ring formation as the key steps. The biological activities of synthetic kalkitoxin and its analogues were evaluated with brine shrimp.     

Formal Total Synthesis of Stevastelins B and B3

The formal total synthesis of stevastelins B and B3 ( 2 and 4 , resp.) have been accomplished employing a highly enantiomerically controlled Lewis acid catalyzed non‐aldol approach to obtain the syn aldol product and temperature controlled hydroboration oxidation reaction to construct four consecutive stereogenic centers. The other key reactions include Sharpless asymmetric epoxidation, macrolactonization, and macrolactamization towards building the core skeleton 2 and 4 .     

3-羟基-4-氨基丁酸及其类似物的合成进展

3-羟基-4-氨基丁酸（简称GABOB）是一类有趣的氨基酸，它的一些类似物如Statine等存在于一些具有抗肿瘤、抗病毒、抗炎症等生理活性的天然产物之中。从治疗的角度讲，3-羟基-4-氨基丁酸也具有重要意义。本文简要介绍GABOB类似物的天然存在及生理活性，并从不同的起始原料出发介绍它们的立体选择性合成。