Synthesis of the First

A "true" allenophane with several rings and allenic bridges was synthesized. The key step in the preparation of 1 was the cyclization to a 28-membered macrocycle (52 % yield) starting from a linear molecule, which already contains three of the four allene units.     

甘油糖脂的合成I.1,2-二－O－脂酰基－3－O－（α-D-吡喃半乳糖基）－sn-甘油的合成

采用一种有效的方法合成了具有不同链长的二脂酰基α-D-半乳糖型甘油糖脂 。将半乳糖烯丙苷化，重结晶得到α－D－半乳糖烯丙苷。随后将糖环的羟基用苄 基保护，再利用OsO4/NMO(N-甲基－N－氧吗啉）的二羟基化条件将1－O烯丙基氧化 成为邻二羟基，得到3－O－（2′，3′，4′，6′－四－O－苄基－α－D－吡喃半 乳糖基）－sn-甘油。其与不同链长的脂酰氯进行脂酰化反应，然后氢解去掉苄基 得到五种二脂酰基α-D-半乳糖苷基甘油。利用^1H NMR,^13C NMR,2D NMR,IR和MS 对化合物的结构进行了确证。     

Total Synthesis of Siomycin A: Completion of the Total Synthesis

The total synthesis of siomycin A ( 1 ), a representative compound of the thiostrepton family of peptide antibiotics, was achieved by incorporating the five synthetic segments A ( 2 ), B ( 3 ), C ( 4 ), D ( 5 ), and E ( 6 ). The dehydropiperidine segment A ( 2 ) was esterified with the dihydroquinoline segment C ( 4 ), and the subsequent coupling with the β‐phenylselenoalanine dipeptide segment D ( 5 ) at the segment C portion followed by lactamization between the segments A and D gave segment A‐C‐D ( 27 ). This was amidated with the pentapeptide segment B ( 3 ) at the segment A portion followed by one‐pot cyclization (between segments A and B) and elongation (with the β‐phenylselenoalanine dipeptide segment E ( 6 ) at the segment A portion), thus furnishing siomycin A ( 1 ).     

A Convenient Synthesis of Hydrophenanthrenes the Synthesis of Ferrugindl and Xanthoperol

We wish to report an approach (equation 1) to hydrophenanthrenes which shows considerable promise of providing a general synthetic route for diterpenes, steroids, triterpenes, and tetraterpenes. Herein we illustrate the utility of this Friedel-Crafts type of procedure^3,6 by describing a synthesis of ferruginol (6) ⁷ and xanthoperol (8).⁸     

费-托合成制液态烃研究进展

天然气先转化为合成气, 再经F ischer-Trop sch 反应合成液体烃类(GTL ) 是近年来天然气转化利用研究的主流。Shell、Sasol、Exxon、Syntroleum 等公司都分别开发了各自的GTL 专利技术。GTL 产品中液体燃料基本上由直链烷、烯烃组成, 具有无硫、无氮、无金属、无芳烃等特点, 是对环境友好的燃料油和化学品。由于合成气生成技术、F-T 合成催化剂和反应工艺的不断改进, 用GTL 技术开发利用边远地区和分散的中小气田的天然气资源在价格上已能和原油竞争。本文对F-T 合成催化剂、反应器及GTL 技术发展动态等方面做了综述, 讨论了其今后的发展趋势, 并指出在我国开展GTL 技术研究的必要性。     

Total Synthesis of the Hamigerans

The first total synthesis of hamigerans D, G, L, and N–Q has been accomplished. A convergent approach was used to build the basic tricarbocyclic ring system bearing a 5‐6‐6 structure. A sequence of oxidative cleavage, homologation, and ring regeneration provided access to the 5‐7‐6 skeleton of hamigeran G. Based on the biogenetic hypothesis, elegant and highly efficient biomimetic transformations of hamigeran G into hamigerans D, N–Q, and L were achieved.     

Synthesis of the perfluoroacetyldiisopropylmethyl radical

A stable trifluoroacetylperfluorodiisopropylmethyl radical has been prepared by interaction of the (-fluorosulfonyloxytetrafluoroethyl)perfluorodiisopropylmethyl radical with anhydrous CsF. This reaction is the first example of a chemical transformation of a C-centered radical which is not resonance-stabilized with retention of the radical center.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 226–227, January, 1993.     

Chemical Synthesis of the Englerins

In the long lasting battle against cancer, Nature sometimes gives a helping hand to researchers to find new drugs for the treatment of diseases and improvement of patients′ well‐being. Englerin A has emerged as a promising anticancer candidate as well as being an exciting synthetic challenge for organic chemists. This focus review summarizes the total syntheses reported to date and the synthetic approaches toward analogues of this fascinating natural product.     

First Synthesis of Cotarnone,the Key Intermediate for the Synthesis of Cotarnine

The first synthesis of cotarnone (2), a degradation product of cotarnine (1), was achieved from 2-hydroxy-3-methoxy-benzaldehyde (o-vanillin), and 2 can be converted to 1 by a known method.     

芳氨基硫脲类化合物的合成

报道了用固-液相转移催化法制得烃基异硫氰酸酯, 不经分离直接与溴代邻肼基苯甲酸作用, 合成11种新的芳氨基硫脲类化合物。讨论了生成烃基异硫氰酸酯的可能机理。     

Synthesis of the silaisocyanoacetylene molecule

The hitherto elusive silaisocyanoacetylene molecule (HCCNSi)-a member of the silaisocyanide family-has been synthesized for the first time through the reaction of the silicon nitride radical (SiN) with acetylene (C(2)H(2)) in the gas phase under single collision conditions. Compared to the isoelectronic reaction of the cyano radical (CN) with acetylene, the replacement of the carbon atom in the cyano group by an isovalent silicon atom has a pronounced effect on the reactivity. Whereas the silicon nitride radical was found to pass an entrance barrier and adds with the nitrogen atom to the acetylene molecule, the cyano radical adds barrierlessly with the carbon atom forming the HCCH(NSi) and HCCH(CN) intermediates, respectively. These structures undergo hydrogen loss to form the linear silaisocyanoacetylene (HCCNSi) and cyanoacetylene molecules (HCCCN), respectively. Therefore, the isovalency of the silicon atom was found to bear little resemblance with the carbon atom having a dramatic effect not only on the reactivity, but also on the reaction mechanism, thermochemistry, and chemical bonding of the isoelectronic silaisocyanoacetylene and cyanoacetylene products, effectively reversing the thermodynamical stability of the nitrile versus isonitrile and silanitrile versus isosilanitrile isomer pairs.     

Synthesis of the monomeric antioxidant

The thermal decomposition oftrans-3,5-di-tert-butyl-4-hydroxy-cinnamic acid (BHC) in the solid state, in aqueous solution and in solutions in organic solvents was studied in order to develop a preparative method for the synthesis of the monomeric antioxidant 3,5-di-tertbutyl-4-hydroxystyrene (BHS). Thermal methods of analysis showed that, during the solidstate decomposition of BHC, its decarboxylation was accompanied by desalkylation and polymerization of the styrenic decomposition products. BHC decarboxylation is aqueous solution was also accompanied by polymerization. A kinetic study of BHC decomposition in organic solvents by 1 H-NMR spectrometry revealed that only the decomposition of BHC in aprotic dipolar solvents such as dimethylsulphoxide and dimethylformamide, at temperatures lower than 150°C, could be used as a preparative method for the synthesis of BHS. The decarboxylation of BHC took place by zero-order kinetics through a mechanism involving the ionization of BHC in the aprotic dipolar solvent. The reaction rate increased drastically with increasing solvent polarity and in the presence of trace amounts of BHC sodium salt. Both monomeric antioxidants, i.e. BHS and BHC, may be used to obtain polymer-bound antioxidants, e.g. by melt-grafting onto polyethylene.

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Zusammenfassung Für die Ausarbeitung eines Verfahrens zur Herstellung des monomeren Antioxidans 3,5-Di-terc-butyl-4-hydroxystyrol (BHS) wurde die thermische Zersetzung vontrans-3,5-Di-terc-butyl-4-hydroxyzimtsäure (BHC) im festen Zustand, in wäßriger Lösung und in Lösungen mit organischen Lösungsmitteln untersucht. Thermoanalytische Verfahren zeigten, daß bei der Feststoffzersetzung von BHC ihre Decarboxylierung durch Desalkylierung und durch Polymerisierung der Styrol-Zersetzungsprodukte begleitet wird. Auch die BHC-Decarboxylierung in wäßriger Lösung wurde durch Polymerisierung begleitet. Mittels 1H-NMR Spektroskopie angefertigte kinetische Studien der Zersetzung von BHC in organischen Lösungsmitteln zeigten, daß die Zersetzung von BHC nur in aprotischen dipolaren Lösungsmitteln, wie z.B. in Dimethylsulfoxid und Dimethylformamid und nur bei Temperaturen unterhalb von 150C als präparatives Verfahren zur Synthese von BHS geeignet ist. Die Decarboxylierung von BHC verlief nach einer Reaktionsordnung 0-ter Ordnung, am Mechanismus ist die Ionisierung von BHC im aprotischen dipolaren Lösungsmittel beteiligt. Die Reaktionsgeschwindigkeit wird mit steigender Lösungsmittelpolarität und in Gegenwart von Spuren von BHC-Natriumsalz drastisch angehoben. Beide monomeren Antioxidationsmittel, d.h. BHS und BHC, können verwendet werden, um Polymerbindungs-Antioxidationsmittel herzustellen, z.B. durch Schmelz-Auf-polymerisieren auf Polyethylen.

     

Synthesis of the hexapeptides glycyl-L-valyl-L-seryl-L-prolyl-L-lysyl-L-leucine

Summary The synthesis of the methyl ester of the hexapeptide N-Cbo-glycyl-L-valyl-L-seryl-L-prolyl-N-tos-L-lysyl-L-leucine, not described in the literature, has been affected.T. G. Shevchenko Kiev State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 41–43, January–February, 1975.     

Synthesis of the landomycinone skeleton

The synthesis of the highly functionalized tetracyclic skeleton of landomycinone (2), the aglycon of landomycins, was performed using two pivotal steps relying on metal-catalyzed reactions. They are (1) a [2 + 2 + 2] cycloaddition of alkynes promoted by Wilkinson's catalyst to build rings B and C concomitantly and (2) a ring-closing metathesis followed by aromatization to build ring D.     

Towards the Synthesis of Azoacetylenes

The synthesis of azoacetylenes (=dialkynyldiazenes) 1 and 2 has been investigated. They represent a still elusive class of chromophores with potentially very interesting applications as novel bistable photochemical molecular switches or as antitumor agents (Fig. 1). Our synthetic efforts have led us alongside three different approaches (Scheme 1). In a first route, it was envisioned to generate the azo (=diazene) bond by photolysis of N,N′‐dialkynylated 1,3,4‐thiadiazolidine‐2,5‐diones that are themselves challenging targets (Scheme 2). Attempts are described to obtain the latter by alkynylation of the parent heterocycle with substituted alkynyliodonium salts. In a conceptually similar approach, the no‐less‐challenging dialkynylated 9,10‐dihydro‐9,10‐diazanoanthracene ( 29 ) was to be generated by alkynylation of the unsubstituted hydrazine 28 (Scheme 6). In a second route, the generation of the N?N bond from Br‐substituted divinylidenehydrazines (ketene‐azines) 35 was attempted in a synthetic scheme involving an aza‐Wittig reaction between azinobis(phosphorane) 36 and (triisopropylsilyl)ketene 37 (Scheme 7). Finally, a third approach, based on the formation of the central azo bond as the key step, was explored. This route involved the extrapolation of a newly discovered condensation reaction of N,N‐disilylated anilines with nitroso compounds (Scheme 11, and Tables 1 and 2) to the transformation of N,N‐disilylated ynamine 55 and nitroso‐alkyne 54 (Scheme 13).     

Synthesis of the himandrine skeleton

The hexacyclic himandrine skeleton 5, which is present in the most complex alkaloids of the tropical rain forest tree Galbulimima belgraveana, has been prepared for the first time. The synthesis begins from the known [3.2.1]benzobicyclooctene intermediate 10. Key steps include a Diels-Alder cycloaddition, Curtius rearrangement, Birch reduction, an intramolecular nucleophilic amination, and a palladium-mediated alkene amination. [reaction: see text]     

Optimizing the Synthesis of Tetratellurafulvalene

A systematic synthetic study of the pi-donor tetratellurafulvalene (TTeF, 6) has resulted in an optimized preparation producing repeatable yields of over 20%. The use of a "one-step" Li/Sn metal exchange/Te(0) insertion procedure and freshly prepared microcrystalline Te(0) serve to drive toward products, the equilibria converting (Z)-1,2-bis(trimethylstannyl)ethylene (1) to its corresponding metal-exchanged vinyllithium species and subsequently to lithium ditellurolate 5. Furthermore, the use of LiCl as an additive to enhance the reactivity of n-BuLi in these metal exchange reactions also increases yields and reproducibility. The slow addition of 1 equiv of tetrahaloethylene during the final cyclization step favors intramolecular reactions which produce TTeF vs intermolecular reactions that lead to oligomeric byproducts. The use of tetrabromoethylene in place of tetrachloroethylene in this step also reduces byproduct formation.     

Synthesis of the hexapeptide L-phenylalanyl-L-prolyl-L-glutamyl-DL-phenylalanyl-L-valyl-L-leucine

Summary The synthesis of the ,-dimethyl ester of N-Cbo-L-phenylalanyl-L-prolyl-L-glutamyl-DL-phenylalanyl-L-valyl-L-leucine, not previously described in the literature, has been effected.T. G. Shevchenko Kiev State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 44–46, January–February, 1975.