Preparation of (1R∗,2S∗,5R∗,6R∗)-1-Methyl-2,5,6-Tribromo-Cyclooctane and 3-Methyl-6,7-Dibromocyclooctene

Abstract

Reaction of 4,5-dibromobicyclo[6.1.0]non-4-ene with anhydrous AlBr₃ forms (1R?,2S?,5R?,6R?)-1-methyl-2,5,6-tribromocyclooctane and 3-methyl-6,7-dibromocyclooctene.

     

Asymmetric synthesis of (−)-(1R,7aS)-absouline

The most efficient and concise asymmetric synthesis of (?)-(1R,7aS)-absouline to date, which was accomplished in eight steps and 20% overall yield from commercially available starting materials, is described. The doubly diastereoselective conjugate addition of lithium (S)-N-benzyl-N-(α-methylbenzyl)-amide to an enantiopure α,β-unsaturated ester derived from l-proline was employed as the key step. Subsequent hydrogenolytic N-debenzylation and acid-promoted cyclisation of the resultant β-amino ester produced the 1-aminopyrrolizidin-3-one scaffold, then reduction with DIBAL-H was followed by DCC-mediated coupling with (E)-p-methoxycinnamic acid to complete the synthesis of (?)-(1R,7aS)-absouline.     

A New Approach to the Construction of Pyrrolizidine and Indolizidine Skeleton: Enantioselective Synthesis of (1S, 7aS)-1-hydroxypyrrolizidine and (1S, 8aS)-1-hydroxyindolizidine

Pyrrolizidineandindolizidineareconunonstructura1elementsofmanynaturallyoccurringalkaloidsfoundinplantsandmicroorganisms.Thediverseandpotentbiologicalactivitiesofthesealkaloidshavedrawnmuchattentioninthestudiesoftheirpharmacologyandpreparation'.Ingeneral,mostconventionalsyntheticmethodologiesinvolvedthefinalformationofoneortwoC-Nbondsofpyrrolizidineandindolizidineskeleton'.andtheseresultedintheinefficientprotectinggroupchemistry,especiallywithrespecttohandlingtheaminoresidueTherefore.themostef…     

Versatile methodology for the synthesis and α-functionalization of (2R,3aS,7aS)-octahydroindole-2-carboxylic acid

An improved strategy for the effective synthesis of enantiomerically pure (2R,3aS,7aS)-octahydroindole-2-carboxylic acid (Oic), based on the formation of a trichloromethyloxazolidinone derivative, has been developed. Additionally, the completely diastereoselective α-alkylation of such oxazolidinone provides a very convenient and concise route to enantiopure α-tetrasubstituted derivatives of this Oic stereoisomer.     

Synthesis of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)-octahydroquinolin-7-ones

A synthesis of the enamine (−)-(1′S)-5-ethyl-1-(1′-phenylethyl)-1,2,3,4-tetrahydropyridine 4 and its application in a synthesis of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)-octahydroquinolin-7-ones 5 and 6 is described. In addition, an X-ray study of 6 is reported. Finally, the preparation of (+)-(4aS,8aR)-4a-ethyl-octahydroquinolin-7-one 7 is described.     

Unexpected retro-Michael reaction of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1-phenylethyl)octahydroquinolin-7-ones

An unexpected retro-Michael reaction of (−)-(1′S,4aS,8aR)-and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)octahydroquinolin-7-ones 1 and 2 is described. In addition, a diastereospecific intramolecular Michael reaction of 3·HCl and 4·HCl is reported.     

(+)-(1S,7aS)-1-羟基-7a-甲基-茚满-4-烯-5-酮的合成及其烷基化反应研究

以2-甲基-2-(3-丁酮)环戊烷-1,3-二酮为原料,经环合和还原反应合成了手性(+)-(1S,7aS)-1-羟基-7a-甲基-茚满-4-烯-5-酮(3);3在其羟基未进行保护情况下与不同芳香侧链进行α,β-不饱和酮的α-位烷基化反应,制备了5个3的衍生物,其结构经1H NMR确证。     

6α-取代的(1S, 7aS)-(+)-1-叔丁氧基-7a-甲基-2, 3, 5, 6, 7, 7a-六氢茚-5- 酮的合成

用化学动力学控制的方法在化合物3的5-C上C=O与6-C发生烯醇化生成锂盐,然后可在6-C位分别引入甲基、烯丙基、苄基、溴以及羟基取代基。产物6、7、8、9a和11经鉴定,除9α外其他都是α和β构型的混合物,其中以α-构型取代物为主。     

6α-取代的(1S, 7aS)-(+)-1-叔丁氧基-7a-甲基-2, 3, 5, 6, 7, 7a-六氢茚-5- 酮的合成

用化学动力学控制的方法在化合物3的5-C上C=O与6-C发生烯醇化生成锂盐,然后可在6-C位分别引入甲基、烯丙基、苄基、溴以及羟基取代基.产物6、7、8、9a和11经鉴定,除9a外其他都是α和β构型的混合物,其中以α构型取代物为主.     

(2S,3aR,7aS)-八氢-1H-吲哚-2-甲酸苄酯的合成

通过合成路线的改进以及合成工艺的优化,方便高效地得到了抗高血压药物群多普利的关键中间体(2S,3aR,7aS)-八氢-1H-吲哚-2-甲酸苄酯.产品结构及绝对构型通过NMR及HPLC进行表征,与文献报道的数据完全一致.最终以99%的对映选择性及13.2%的产率得到目标化合物.为群多普利关键中间体的合成提供了一条可工业化的途径.     

3-((1R,3aS,3aS,10aR)-十氢-(1H,4H)-吡啶并[1,6]萘啶-1-基)丙-1-胺的合成

以廉价易得的苦参碱为起始原料,经过开环、酯化反应、水解等步骤,得到4-((3aS,3aS,10aR)-2-(叔丁氧基羰基)十氢-(1H,4H)-吡啶并[1,6]萘啶-1-基)丁酸(5)。5再经过Curtius重排反应,得到叔丁基(1R,3aS,3aS,10aR)-1-(3-(((苄氧基)羰基)氨基)丙基)八氢-(1H,4H)-吡啶并[1,6]萘啶-2(3H)-羧酸叔丁酯(6)。然后,6脱去Cbz基团得到(1R,3aS,3aS,10aR)-1-(3-氨基丙基)八氢-(1H,4H)-吡啶并[1,6]二氮杂萘-2(3H)-羧酸叔丁酯(7),最后,7脱去Boc基团成功得到苦参碱衍生物的重要中间体3-((1R,3aS,3aS,10aR)-十氢-(1H,4H)-吡啶并[1,6]萘啶-1-基)丙-1-胺(8),总收率28%。目标化合物和中间体的结构经¹H NMR, ¹³C NMR和HR-MS确证。      

Reactive epitaxy of beryllium on Si(1 1 1)-(7×7)

Scanning tunneling microscopy (STM) and photoelectron spectroscopy (PES) have been used to investigate the nucleation, growth, and structure of beryllium on Si(1 1 1)-(7×7). STM indicates that a chemical reaction occurs at temperatures as low as 120 K, resulting in a nano-clustered morphology, presumed to be composed of a beryllium silicide compound. Upon annealing to higher temperatures, PES data indicate that beryllium diffuses into the selvage region. High temperature annealing (∼1175 K) results in the formation of a universal ring cluster structure suggesting a Be–Si bond length less than 2.5 Å, in agreement with previous calculations regarding hypothetical Be₂Si.     

1, 7-二酮的成环反应 Ⅲ. 1, 7-二苯庚二酮-1, 7的酮-环醇互变异构

1,6-二酮在碱性试剂存在下能生成环戊烯衍生物,如1,6-二苯己二酮-1,6(1a)在氢氧化钾的乙醇溶液中,生成1-苯-2-苯甲酰环戊烯(2a)和2-苯-3-苯甲酰环戊烯(3a)^[1].1,7-二苯庚二酮-1,7(1b)也生成相应的环己烯的衍生物(2b,3b).^[2]     

Synthesis and Crystal Structure of N-[（3aR,4R,4aR,5aS,6S,6aS）-1,3-Dioxooctahydro-4,6-ethenocyclopropa[f]isoindol-2（1H）-yl]-3-（trifluoromethyl）phenylmethanimine

The crystal structure of the title compound(C19H15F3N2O2,Mr = 360.33) was determined by single-crystal X-ray diffraction.The crystal belongs to triclinic,space group P1,with a = 6.5604(7),b = 13.9614(16),c = 18.1790(18) ,α = 102.749(7),β = 97.542(6),γ = 94.355(4)°,V = 1600.5(3) 3,Z = 4,Dc = 1.495 g/cm3,λ(MoKα) = 0.71070,F(000) = 744,μ(MoKα) = 0.122 mm-1,R = 0.0434 and wR = 0.1051.A total of 7590 unique reflections were collected,of which 5429 with |F|2 ≥ 2σ|F|2 were observed.The two cyclohexene rings in the molecule adopt boat-boat conformations with the deviations of ring atoms C(9) and C10 from the C(5)/C(6)/C(7)/C(8) plane(Ⅰ) by 1.1204(0.0023) and 1.1132(0.0023) ,respectively,whereas from the C(2)/C(3)/C(5)/C(8) plane(Ⅱ) by 1.1627(0.0022) and 1.1818(0.0021) ,respectively.In the cyclopropane and lactam rings,atoms C(11) and N(1) point towards the double bond of C(9)-C(10) and the dihedral angle between the ring plane(Ⅲ) containing C(1),C(2),C(3) and C(4) and plane(IV) consisting of C(6),C(7) and C(11) is 55.76(0.07)°.The dihedral angles between planes Ⅳ and Ⅰ and Ⅱ and Ⅲare 63.58(0.07)° and 58.10(0.06)°,respectively.The dihedral angle between the benzene ring C(13)～ C(18) and plane Ⅳ is 42.41(0.06)°.     

1～7岁儿童309例发铁观察

１～７岁儿童发铁检查３０９例，其中血红蛋白正常范围１３２例，血红蛋白９～１２ｇ％１７７例．血红蛋白正常范围组，发铁低于正常值占２６．５％，有部分儿童存在非贫血型铁缺乏．血红蛋白９～１２ｇ％组，发铁低于正常值占１９．７％．血红蛋白下降的儿童，仅部分是铁元素缺乏引起．铁元素缺乏的发病率，两组相比，无显著性差异（Ｐ＞０．０５）     

二氧六环-水体系的^1H和^1^7O NMR研究

本工作用配位平衡和快交换方法定量描述了二氧六环水体系中^1H和^1^7O化学位移随浓度的变化. 讨论了未配位水的结构破坏程度及其存在形式.     

应用^1H NMR法比较7种海藻酸钠序列结构

海藻酸钠的质量和应用与其序列片段比例密切相关,该研究将海藻酸钠温和水解成20个单体长度的片段后,采用1H NMR法分别测定了7种不同来源海藻酸钠样品的序列结构含量,图谱数据分析显示3种来源相同、粘度不同的国产样品M/G比例差别不大,分别为1.55(220 cps)、1.74(430 cps)和1.58(530 cps);而4种进口样品因来源不同,其比例差别较大,分别为1.35(Kecosol)、0.47(DMB)、1.14(LVCR)和1.42(HVCR).7种样品的η值均为0 ～1,表明其结构以嵌段共聚为主,其中DMB型号的样品以GG嵌段居多,而其余6种均以MM嵌段居多.此结果表明采用核磁共振法可以较准确地测定海藻酸钠的序列结构及其各片段的比例,方法可用于海藻酸钠的质量控制,对其药用具有实际指导意义.     

An Efficient Approach to 6, 7-Disubstituted-1H-quinoxalin-2-ones

A novel approach to the synthesis of 6, 7-disubstituted-1H-quinoxalin-2-ones is described.The title compounds were regioselectively prepared by starting from substituted phenylamines andchloroacetyl chloride through the efficient sequence of acylation, nitration, reduction, intramolecularalkylation, and oxidation. 6, 7 -Disubstituted-1H-quinoxalin-2-ones, regioselective, substituted phenylamine.     

Efficient Synthesis of the C1-C7 Fragment of Didemnaketal A

The stereoselective synthesis of the CI-C7 fragment (3R,4S,6R)-3,4-di[(tert-butyldimethylsilyl)oxy]-7-hydroxy-6-methylheptan-2-one, which is the crucial intermediate for synthesis ofthe HIV-1 protease inhibitive didemnaketals, was developed via 12 steps from the natural ( )-pulegone.