Enantiospecific Synthesis of Natural (−)-Cocaine and Unnatural (+)-Cocaine from d- and l-Glutamic Acid
摘要:
Natural (-)-cocaine and unnatural (+)-cocaine have been synthesized enantiospecifically from D- and L-glutamic acid, respectively. The axial-equatorial substitutents were introduced by a stereo- and regiospecific dipolar cycloaddition to the corresponding (LR,5S)- and (1S,5R)-N-BOC-nortropenes with (ethoxycarbonyl)formonitrile N-oxide. A sequence of subsequent stereochemically controlled transformations converted the fused isoxazoline to the requisite P-hydroxy ester. Synthesis of the key intermediate N-BOC-nortropenes involved construction of the 8-azabicyclo[3.2.1]octane framework by Dieckmann condensation of cis-5-substituted D-and L-proline esters. For comparison, (1R,SS)-N-BOC-nortropene also was derived by degradation from natural cocaine. The cis-5-substituted D-and L-proline esters were obtained by sulfide contraction and subsequent catalytic hydrogenation to induce stereospecifically the C-5 stereochemistry from D-and L-thiopyroglutamate, which in turn were prepared from D-and L-glutamic acids, respectively.
Enantiospecific Synthesis of Natural (−)-Cocaine and Unnatural (+)-Cocaine from d- and l-Glutamic Acid
摘要:
Natural (-)-cocaine and unnatural (+)-cocaine have been synthesized enantiospecifically from D- and L-glutamic acid, respectively. The axial-equatorial substitutents were introduced by a stereo- and regiospecific dipolar cycloaddition to the corresponding (LR,5S)- and (1S,5R)-N-BOC-nortropenes with (ethoxycarbonyl)formonitrile N-oxide. A sequence of subsequent stereochemically controlled transformations converted the fused isoxazoline to the requisite P-hydroxy ester. Synthesis of the key intermediate N-BOC-nortropenes involved construction of the 8-azabicyclo[3.2.1]octane framework by Dieckmann condensation of cis-5-substituted D-and L-proline esters. For comparison, (1R,SS)-N-BOC-nortropene also was derived by degradation from natural cocaine. The cis-5-substituted D-and L-proline esters were obtained by sulfide contraction and subsequent catalytic hydrogenation to induce stereospecifically the C-5 stereochemistry from D-and L-thiopyroglutamate, which in turn were prepared from D-and L-glutamic acids, respectively.
Die sterischen Bedingungen der Fragmentierungsreaktion I. Teil. Stereoisomere 3-Chlortropane. Fragmentierungsreaktionen, 14. Mitteilung
作者:A. T. Bottini、C. A. Grob、E. Schumacher、J. Zergenyi
DOI:10.1002/hlca.19660490815
日期:——
The steric requirements for the synchronous fragmentation of γ-aminohalides as previously postulated have been confirmed by a study of the solvolysis of stereoisomeric 3β- and 3β-chloro-tropanes and -nortropanes. 3β-chloro-tropanes (7 a) and 3β-chloro-nortropane (7 b), which fulfil the stereoelectronic requirements, undergo quantitative fragmentation in 80 vol.% ethanol. They react 1.35 × 104 and 1
Cationic Tropidinyl Scandium Catalyst: A Perfectly Acceptable Substitute for Cationic Half-Sandwich Scandium Catalysts in <i>cis</i>-1,4-Polymerization of Isoprene and Copolymerization with Norbornene
作者:Siqian Liu、Gaixia Du、Jianyun He、Yingyun Long、Shaowen Zhang、Xiaofang Li
DOI:10.1021/ma500740m
日期:2014.6.10
tris(trimethylsilylmethyl) rare earth metal complexes with the readily available natural product tropidine. The polymerization experiments indicate that the monotropidinyl scandium dialkyl complex 1 displays reactivity akin to that of the analogous monocyclopentadienyl scandium dialkyl complexes. In the presence of activator and a small amount of AlMe3, complex 1 exhibits similar activities (up to 1.6
不同的非金属茂稀土金属烷基络合物,例如单tropidinyl(Trop)di二烷基络合物(Trop)Sc(CH 2 SiMe 3)2(THF)(1),ditropidinyl钇烷基络合物(Trop)2 Y(CH 2 SiMe 3)( THF)(3)以及带有一个四齿双阴离子6 - N-甲基-1,4-环庚二烯基(NMCH)配体[(NMCH)Lu(CH 2 SiMe 3)(THF)]的双核烷基络合物2(2)已通过一锅酸碱反应,通过使用三(三甲基甲硅烷基甲基)稀土金属配合物与现成的天然产品托帕定进行了高收率的合成。聚合实验表明,单斜环炔基scan二烷基络合物1显示出与类似的单环戊二烯基scan二烷基络合物相似的反应性。在存在活化剂和少量AlMe 3的情况下,配合物1表现出相似的活性(高达1.6×10 6 g mol Sc –1 h –1),但比cis -1,4-选择性(高达100%)高(C 5 H
Efficient Direct Synthesis of Tropidinyl Titanium and Zirconium Complexes by Allylic CH-Activation of 8-Methyl-8-azabicyclo[3.2.1]oct-2-ene (Tropidine)
A CH-activation and deprotonation of 8-methyl-8-azabicyclo[3.2.1]oct-2-ene (tropidine, 1) occurs upon reaction with TiCl4 and ZrCl4 to afford the allyl complexes monotropidinyl titanium trichloride (4) and ditropidinyl zirconium dichloride (7), respectively. Tropidine (1) itself acts as the HCl scavenger, and the reactions are accompanied by the formation of 1 equiv of the hydrochloride 1·HCl. The