Benzothiazines in synthesis. Formal synthesis of erogorgiaene

A benzothiazine, readily available in enantiomerically pure form via a completely selective, intramolecular addition of a sulfoximine-stabilized carbanion to an α,β-unsaturated ester, could be converted to a precursor to erogorgiaene in good overall yield.     

金属蒸气合成在金属有机合成中的应用

本文简要地介绍了金属蒸气合成法的基本原理、仪器和实验技术, 并按金属原子分别与炔、单烯、多烯、环烯、芳烃体系、卤代烃、有机混和物的反应及有机金属硼化合物的合成, 对金属蒸气合成法在金属有机合成中的应用进行了讨论。     

Asymmetric synthesis of cyclobutanones: synthesis of cyclobut-G

A simple, efficient, and stereoselective approach has been developed for obtaining chiral cis- and trans-disubstituted cyclobutanones from readily available alkyl- and functionalized alkyl-substituted enol ethers. The usefulness of these cyclobutanones is illustrated by an enantioselective synthesis of cyclobut-G (Lobucavir).     

Total synthesis of apoptolidin: completion of the synthesis and analogue synthesis and evaluation

The total synthesis of apoptolidin (1) is reported together with the design, synthesis, and biological evaluation of a number of analogues. The assembly of key fragments 6 and 7 to vinyl iodide 3 via dithiane coupling technology was supplemented by a second generation route to this advanced intermediate involving a Horner-Wadsworth-Emmons coupling of fragments 22 and 25. The final stages of the synthesis featured a Stille coupling between vinyl iodide 3 and vinylstannane 2, a Yamaguchi lactonization, a number of glycosidations, and final deprotection. The developed synthetic technology was applied to the construction of several analogues including 74, 75, and 77 which exhibit significant bioactivity against tumor cells.     

Radical-mediated synthesis of 3,4-dihydroisocoumarins: total synthesis of hydrangenol

A radically promoted synthesis of 3,4-dihydroisocoumarins has been achieved in moderate to good yields using titanocene(III) chloride (Cp₂TiCl) as the radical initiator. The total synthesis of (±)-hydrangenol has been completed using this radical technology. Cp₂TiCl was prepared in situ from commercially available titanocene dichloride (Cp₂TiCl₂) and Zn-dust in THF under argon.     

Benzothiazines in synthesis. Toward the synthesis of pseudopteroxazole

[reaction: see text] The tricyclic benzothiazine 15 was prepared in a straightforward fashion via a completely stereoselective intramolecular Friedel-Crafts alkylation. This compound represents a potential precursor to the antitubercular agent, pseudopteroxazole. Its synthesis proceeded via a completely selective, intramolecular addition of a sulfoximine-stabilized carbanion to an alpha,beta-unsaturated ester, followed by functional group manipulations.     

Formal synthesis of nitidine through palladium-catalyzed isocoumarin synthesis

The isoquinolone intermediate 9 for the synthesis of nitidine was synthesized through palladium-catalyzed formation of isocoumarin 7 from o-styrylbenzoic acid derivative 5, which was prepared from palladium-catalyzed coupling reactions of aryl iodide 1 and 2 with vinylsilane.     

Recent developments in oligosaccharide synthesis: tactics,solid-phase synthesis and library synthesis

Oligosaccharides, commonly found on the cell surfaces, are deeply involved in a variety of important biological functions, yet demanding difficulties synthesizing such structures limit the investigation of their functions. Technologies to chemically synthesize these oligosaccharides have dramatically advanced during the last two decades mainly due to the introduction of good anomeric leaving groups. In addition, tactical analyses have been addressed to enhance the overall efficiency of oligosaccharide synthesis. Based on the advancement of solution-phase chemistry, solid-phase technologies are being investigated in connection with the current trend of combinatorial chemistry and high throughput screening. This review summarizes the necessary solution-phase methodologies, the status of solid-phase synthesis of oligosaccharides, and combinatorial synthesis of oligosaccharide libraries.     

Studies towards the total synthesis of Sch 56036; isoquinolinone synthesis and the synthesis of phenanthrenes

The isoquinolinone hemisphere of Sch 56036 has been prepared using a modified Pomeranz-Fritsch reaction and the synthesis of the phenanthrene core has been modelled via a Suzuki coupling and subsequent ring closing metathesis.     

Tellurium in organic synthesis: synthesis of bioactive butenolides

Reduction of (Z)-β-butyltelluro-enones gives the corresponding γ-hydroxy vinylic tellurides with retention of the double bond configuration. Reaction of γ-hydroxy vinylic tellurides with 2 equiv of n-butyllithium produces 1,4-C,O-dianions, which on reaction with carbon dioxide give the corresponding butenolides.     

Benzothiazines in synthesis. A total synthesis of pseudopteroxazole

An enantioselective total synthesis of the naturally occurring antitubercular agent pseudopteroxazole is described. The synthesis is organized around the use of a stereoselective, intramolecular addition of a sulfoximine carbanion to an alpha,beta-unsaturated ester to form an enantiomerically pure benzothiazine. Other important processes include a completely stereoselective intramolecular Friedel-Crafts alkylation and a stereoselective and regioselective hydrogenation. [structure: see text]     

生物质合成气一步法合成LPG的实验研究

由生物质气化合成液体燃料(甲醇、二甲醇和低碳烃类),是理想的碳中性绿色燃料,将其用作城市交通和民用燃料,已经引起全世界的广泛关注.[1,2]     

Toward the synthesis of thapsigargin: enantioselective synthesis of 7,11-dihydroxyguaianolides

[reaction: see text] The enantioselective synthesis of a 7,11-dihydroxyguaianolide bearing the stereochemistry present in thapsigargin, a potent and selective inhibitor of the Ca(2+) SERCA-ATPase pumps, is described. Starting from (+)-dihydrocarvone, the synthesis presents two key steps. The first one involves the photochemical rearrangement of a gamma,delta-unsaturated ketone eudesmane into the corresponding guaiane. The second step consists of the regioselective oxidation of an unprotected tetrahydroxylated ketone to provide a dihydroxylactone with the required stereochemistry.     

Stereocontrolled synthesis of functionalized 1-azaspirans : Efficient synthesis of perhydrohistrionicotoxin

A formal total synthesis of perhydrohistrionicotoxin (H₁₂-HTX) is described based on a stereocontrolled α-acyliminium ion-olefin cyclisation. In the key step of the synthesis three asymmetric C atoms (C₆ C₇ and C₈) are introduced in a single operation leading to the formation of the spiro formate ester 15. Compound 15 is converted to the spirothiolactam alcohol 17, a known precursor of H₁₂-HTX.The versatility of the synthetic approach is further demonstrated by the stereocontrolled syntheses of other functionalized 1-azaspirans, viz the 6-Endo-Trig products 20 and 24 and the 5-Exo-Trig products 26 and 28. The formation of the latter two compounds is remarkable with respect to the mechanism.¹³C NMR data of a series of 1-azaspirans are provided, which inter alia show the existence of a conformational equilibrium in 1-azaspiro alcohol 16,Mass spectral criteria are used for assignment 5-Exo-or 6-Endo-cyclisation products.     

Formal synthesis of dictyostatin and synthesis of two dictyostatin analogues

A formal convergent synthesis of dictyostatin from (R)-Roche ester is described. Synthetic highlights include a Ni-catalyzed Nozaki-Hiyama-Kishi coupling between an aldehyde and a Z vinyl iodide to assemble the two main fragments, a diastereoselective Myers alkylation, a stereoselective Evans aldolization, two asymmetric Duthaler crotyltitanations, and a stereoselective Pd-catalyzed Marshall allenylindium addition to install the stereogenic centers of dictyostatin. The synthesis of (9R)-epi-dictyostatin and a new ring-contracted dictyostatin isomer were also achieved.     

Biology-oriented synthesis

Which compound classes are best suited as probes and tools for chemical biology research and as inspiration for medicinal chemistry programs? Chemical space is enormously large and cannot be exploited conclusively by means of synthesis efforts. Methods are required that allow one to identify and map the biologically relevant subspaces of vast chemical space, and serve as hypothesis‐generating tools for inspiring synthesis programs. Biology‐oriented synthesis builds on structural conservatism in the evolution of proteins and natural products. It employs a hierarchical classification of bioactive compounds according to structural relationships and type of bioactivity, and selects the scaffolds of bioactive molecule classes as starting points for the synthesis of compound collections with focused diversity. Navigation in chemical space is facilitated by Scaffold Hunter, an intuitively accessible and highly interactive software. Small molecules synthesized according to BIOS are enriched in bioactivity. They facilitate the analysis of complex biological phenomena by means of acute perturbation and may serve as novel starting points to inspire drug discovery programs.     

Heterodiene synthesis

Transamination occurs in the reaction of amidines of benzoic and trichloro- and trifluoroacetic acids with azomethines obtained from aniline and various aromatic aldehydes; two molecules of the resulting benzylideneamidines react to give 1,2-dihydro-sym-triazines via the Diels-Alder scheme with the liberation of imino aldehydes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 281–283, February, 1973.See [1] for communication IV.     

Recent progress toward synthesis of chlorosulfolipids: total synthesis and methodology

Chlorosulfolipids (CSLs) are an intriguing family of natural products featuring highly chlorinated linear hydrocarbon skeletons. Although CSLs were first isolated in 1962, chemical synthesis of CSLs was hampered because relevant methods for stereoselective construction of the polychlorinated motifs of CSLs were scarce. Since Carreira’s first total synthesis of the CSL mytilipin A in 2009, several groups, including our own, have reported total syntheses of CSLs. As a result of these total syntheses, important progress has been made in the development of reliable synthetic methods for stereoselective polychlorination. In this digest, we summarize the total syntheses of CSLs by focusing on synthetic methods for stereoselective polychlorination of the organic frameworks of CSLs.     

离子热法合成沸石咪唑骨架材料及其溶解-结晶机理研究

基于沸石咪唑骨架材料在离子液体和低共熔溶剂中冷却结晶的析出方式,开发了一种离子热法合成沸石咪唑骨架材料的新途径,采用X射线衍射、扫描电镜、核磁共振光谱、红外光谱以及热重分析等方法对制备的产物进行了表征,研究了合成条件对产物结晶度、尺寸和形貌的影响,探讨了沸石咪唑骨架材料在离子热合成体系中的溶解-结晶析出机理.研究发现,冷却速率能够影响产物形貌,急速冷却时,sod(RCSR代码)型产物的形貌为球形,zni(RCSR代码)型产物为棒状或平板状;程序控制冷却时,sod型产物的形貌为多面体,zni型产物呈团簇状.     

Solid-phase synthesis of beta-mannosides

The linkage of S-phenyl 2,3-di-O-benzyl-alpha-D-thiomannopyranoside to a cross-linked polystyrene support in the form of its 4,6-O-polystyrylborinate ester is described. The activation of this polymer-supported mannosyl donor is achieved at -60 degrees C in dichloromethane in the presence of 2,4,6-tri-tert-butylpyrimidine with the combination 1-benzenesulfinyl piperidine and trifluoromethanesulfonic anhydride. Addition of the donor alcohol at -60 degrees C followed by warming to room temperature and subsequent cleavage from the resin by gentle heating in aqueous acetone yields anomerically pure 2,3-di-O-benzyl-beta-D-mannopyranosides in excellent yield. Successful, diastereoselective coupling is demonstrated with a range of primary, secondary, and tertiary glycosyl acceptors, including typical carbohydrates and threonine derivatives.