Synthesis of ( )-5α-Hydroxy-β-selinene and (-)-5β-Hydroxy-β-selinene

Eudesmanederivativeshavebeendrawingconsiderableattentionduetotheirwidespectrumofbiologicalproperties,particularlyantifeedant,cellgroWthinhibitoryandplantgroWthregulatingactivitiesl'2.Recently,twoepimericeudesmanederivatives( )-5a-hydroxy-6-selinene1and(-)-56-hydroxy-6-selinene2wereisolated3fromtheaerialpartsofCSubtraPicaFMell.,andtheirstructuresweredeterminedbyspectroscopicmethods.Herein,wereportafacilesynthesisofbothtwodiastereomers1and2from( )-dihydrocarvone3infivesteps,usingtheregioselect…     

β-(4-Nitrophenyl)-α,α′-dichlor-hydracrylsäure

Zusammenfassung Basenkatalysierte Kondensation von 4-Nitrobenzaldehyd mit Dichloracetonitril in Methanol lieferte ein als Methyliminoäther aufgefaßtes Kondensationsprodukt, dessen salzsaure Hydrolyse die im Titel genannte Säure ergab. Sie erwies sich als völlig ident mit einem Präparat, das in einer vorigen Arbeit durch Hydrolyse des 2-[-(4-Nitrophenyl)--oxy-,-dichlormethyl]-oxazolin erhalten wurde.     

Nitroderivate vonβ,β,β-Trihalo-α,α-bis-(4-alkoxybzw. 4-oxy-phenyl)-äthanen

Zusammenfassung Auf Grund von Modellbetrachtungen wurde die Existenz der in der Literatur beschriebenenOctanitro-Derivate von ,,-Trihalo-,-bis-(4-alkoxy-phenyl)-äthanen in Zweifel gezogen. Entsprechende Untersuchungen ergaben, daß es sich bei ihnen umTetranitro-Verbindungen handelt und daß es nicht möglich ist, diese DDT-Analogen mehr als vierfach zu nitrieren. Die Konstitution der Tetranitro-Verbindungen wurde durch Abbau bewiesen: Beim ,,-Trichlor-,-bis-(3,5-dinitro-4-methoxy-phenyl)-äthan (II) durch Überführung in das entsprechende Keton (VII), beim ,,-Trichlor-,-bis-(3,5-dinitro-4-äthoxy-phenyl)-äthan (IV) durch Entalkylierung und Methylierung zu II. Der Beweis der 3,3, 5,5-Stellung der Nitrogruppen in II und IV ist auch für andere Tetranitro-Derivate von ,,-Trihalo-,-bis-(4-X-phenyl)-äthanen (X=Substituenten I. Ordnung) von Bedeutung.Mitt. II der Reihe: Stereochemische Untersuchungen in der Diphenylmethanreihe.     

Dehydrochlorination of trichloro(α,β-dichlorophenethyl)-silane and of trichloro[α-chloro-α-(chloromethyl)benzyl]silane

Summary The general character of the rearrangement undergone by ,-dichloroalkyltrichlorosilanes in the course of their dehydrochlorination by means of aluminum chloride was confirmed by reference to a new example of the reaction.     

Possible conformations of the seven-membered rings and relative stabilities of 1β,5α,6β,7α(H)- and 1α,5α,6β,7α(H)-guai-11(13)-en-6,12-olides

A calculation has been made by the method of molecular mechanics, using the MM2 program, of a number of stereomeres of 1,5,6,7(H)- and 1,5,6,7(H)-guai-11(13)-en-6,12-olides. The possibilities of the adoption by the seven-membered ring of particular conformations according to the type of its linkage with the 5-membered carbocycle have been considered. Questions of the influence of the orientation of the Me groups on the degree of distortion of the conformation of the seven-membered ring from the ideal and the relative stabilities of the various conformers are discussed.A. N. Nesmeyanov Institute of Organometallic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 198–203, March–April, 1991.     

Synthesis and Reactivity of (β-Amino-α-acylalkenyl)phenyliodonium Salts

During the last few years alkenyl(phenyl)iodonium salts have risen from mere chemical curiosities to valuable synthetic intermediates. [1] Because of an excellent leaving group ability of a phenyliodonyl moiety, alkenyl(phenyl) iodonium salts undergo nucleophilic vinyl substitutions under mild conditions, thus providing a useful route for the synthesis of various kinds of olefins. Recently, some of functionalized alkenyl iodonium salts have been prepared. [2]     

Enzymatic resolution of (±)-2-(Nβ-t-butoxycarbonyl-Nα-methylhydrazino)cycloalkanols

Racemates of cis- and trans-2-(N_β-t-butoxycarbonyl-N_α-methylhydrazino)cyclopentanols and -cyclohexanols 1–4 were resolved through lipase PS- or Novozym 435-catalysed asymmetric acylation of the secondary OH group at the (R)-stereogenic centre. High enantioselectivity (E >200) was observed when vinyl acetate or vinyl butyrate was used in diisopropyl ether, resulting in the enantiopure hydrazino esters 1a–4a and hydrazino alcohols 1b–4b. Methanolysis of the esters 1a–4a afforded the corresponding 2-hydrazinocycloalkanols 1c–4c (ee usually >95%).     

α(β)-(2,4-二叔丁基苯氧基)酞菁钴的合成与表征

用概率缩合法合成了单取代酞菁配合物α-(2,4-二叔丁基苯氧基)酞菁钴和-β(2,4-二叔丁基苯氧基)酞菁钴。溶解度及质谱分析均表明此类单一取代基酞菁仍有很大的聚集倾向,除吡啶等具有强配位能力的溶剂以外,在大多数有机溶剂中溶解度均较小,在质谱中可检测到强度仅次于单体的二聚体信号。在THF和DMF溶剂中,与卢位单取代相比,α位单取代使酞菁的Q带最大吸收波长红移约5nm。     

α-氨基-β-酮酸酯(β-含氧二肽)的合成研究

对α-氨基-β-酮酸酯(β-含氧二肽)的合成进行了探讨.以Boc保护的(L)-缬氨酸及(L)-异亮氨酸为原料,分别与(D,L)-苏氨酸甲酯盐酸盐进行偶合,再用Dess-Martin试剂(DMP)氧化,分别以48%和38%的总收率得到相应的氨基酮酸酯二肽化合物.     

Possible conformations and relative stability of the 7-membered ring in 1α,5β,6,7α(H)-and 1β,5α,6,7α(H)-guai-11(13)-en-6,12-olides

Stereoisomers of 1,5,6,7(H)- and 1,5,6,7(H)-guai-11(13)-en-6,12-olides are calculated using molecular mechanics. The possibility of forming various conformations in the 7-membered ring is examined as a function of the fusion to the 5-membered C-ring. The effect of the methyl orientation on the conformation of the 7-membered ring and the relative stability of the conformers are discussed.Insitute of Phytochemistry, Karaganda, fax (3212)-43-37-73. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 54–56, January–February, 2000.     

四-α(β)-(4-吡啶氧基)酞菁锌的光物理性质研究

测定了新合成的α位取代和β位取代的四-(4-吡啶氧基)酞菁锌配合物的UV-Vis吸收光谱、荧光光谱及激发单重态寿命、纳秒瞬态吸收光谱与激发三重态寿命.在此基础上,与相关配合物进行了比较,探讨了取代基及其取代位置对酞菁锌配合物的吸收光谱、激发单重态寿命及激发三重态寿命的影响.     

α-Hydroxy- and (α-acyloxyimino)benzylphosphonates

N-Hydroxyfluorobenzimidoylphosphonates and their O-acyl derivatives are synthesized. Reaction of phosphorylated oximes with sulfinyl chloride proceeds with rearrangement and leads to synthetically prospective N-sulfonylimidoylphosphonates. By the method of ¹⁹F NMR are revealed values of σ-constants of N-hydroxy- and N-acyloxy substituted imidoylphosphonate groups.     

Palladium-catalyzed stereoconvergent formylation of (E/Z)-β-bromo-β-fluorostyrenes: straightforward access to (Z)-α-fluorocinnamic aldehydes and (Z)-β-fluorocinnamic alcohols

We report here the stereoconvergent formylation of (E/Z)-β-bromo-β-fluorostyrene mixtures with carbon monoxide and sodium formate catalyzed by palladium. Optimization of reaction conditions leads to the corresponding pure (Z)-α-fluorocinnamaldehydes in good yields. The reaction was extended to styrenes bearing electro-attracting or electro-donating groups. The obtained α-fluoroaldehydes were smoothly reduced to the corresponding (Z)-β-fluorocinnamic alcohol by NaBH(4). The reaction could be performed on functionalized substrates as demonstrated by the access to the glucoside of β-fluoroconiferyl alcohol, (Z)-β-fluoroconiferin, a strong inhibitor of lignin polymerization.     

从N-Fmoc-L-α-氨基酸合成同系物N-Fmoc-L-β-氨基酸(Ⅱ)

描述了应用Amdt-Eistert反应合成两种含酰胺基的N-Fmoc-L-β-氨基酸的方法,讨论了在Wolff重排过程中,N-Fmoc-L-β-谷氨酰胺重氮甲基酮和N-Fmoc-L-α-天冬酰胺重氮甲基酮的各自特点及反应过程中生成的副产物.     

(α,3pxn) or (α,αpxn) reactions on natural dysprosium

The (EC, ⁺) decay of¹⁶⁸Hf, produced by the¹⁵⁶Gd (¹⁶O,4n) reaction, has been studied, with high efficiency HPGe coaxial detectors, using on-line measurements with the RACHEL setup. Off-line measurements were also carried out using catcher collection technique. Energies and intensities of 119 -lines are reported among these only two were known in the earlier study ofChu andReednick. The¹⁶⁸Lu level scheme built on the basis of single - and X-spectra and - coincidence measurements, allows the interpretation of 79 -transitions, between 38 excited states reported for the first time.     

Stereoelective Conversion of Ethyl Pipecolinate into (±)-α- and (±)-β-Conhydrins

Reaction of ethyl N-benzhydrylpipecolinate with ethylmagnesium bromide in the presence of catalytic amount of titanium(IV) isopropoxide furnished in a high yield the corresponding hydroxypropyl-substituted piperidine that by treating with alcoholic alkali was quantitatively converted into 1-benzhydryl-2-propionylpiperidine. The reduction in the latter of carbonyl group with lithium aluminum hydride or sodium borohydride in methanol gave rise prevailingly to threo-aminoalcohol. With sodium borohydride in the presence of cerium chloride an erythro-aminoalcohol was the main product. Deprotection of the nitrogen atom from the benzhydryl group of the aminoalcohols obtained provided racemic - and -conhydrines.     

Synthesis and hetero-Diels-Alder reactions of (E)-α-perfluoroalkanesulfonyl-α,β-unsaturated ketones

Catalyzed by ammonium acetate, the Knoevenagel reactions of β-keto perfluoroalkanesulfones 1 with aromatic aldehydes 2 afforded α-perfluoroalkanesulfonyl-α,β-unsaturated ketones 4 in moderate to good yields. The possible mechanism for the reactions was proposed. These fluorine-containing α,β-unsaturated ketones, which are electron-poor 1-oxa-1,3-butadienes, could be used in inverse electron demand hetero Diels-Alder (HDA) reaction with electron-rich olefins to give tetrasubstituted dihydropyrans 6 in quantitative yields.     

A facile stereoselective synthesis of (Z)-α-arylsulfonyl-α,β-unsaturated ketones

Palladium-catalyzed hydrostannylation of acetylenic sulfones 1 in benzene at room temperature gives highly regio- and stereoselectively (E)-α-stannylvinyl sulfones 2 in high yields. (E)-α-Stannylvinyl sulfones 2 are new difunctional group reagents which undergo Stille coupling reactions with acyl chlorides 3 to afford stereoselectively (Z)-α-arylsulfonyl-α,β-unsaturated ketones 4 in good yields. A one-pot stereoselective synthesis of (Z)-α-arylsulfonyl-α,β-unsaturated ketones 4 has also been achieved by tandem hydrostannylation-Stille coupling reaction of acetylenic sulfones 1 under mild conditions.