Approach to Animated Anthracyclines via an Intramolecular Marschalk Reaction

An anionic cyclization based approach to a novel daunomycin analog is described.     

Synthesis of Optically Active Vasicinone Based on Intramolecular Aza-Wittig Reaction and Asymmetric Oxidation(1)

Both optical isomers of a quinazoline alkaloid, vasicinone, were synthesized by two different methods. The first method used (3S)-3-hydroxy-gamma-lactam as a chiral synthon, which was, after O-TBDMS protection, o-azidobenzoylated followed by treatment with tri-n-butylphosphine to afford (S)-(-)-vasicinone via the tandem Staudinger/intramolecualr aza-Wittig reaction. The second method utilized asymmetric oxygenation of deoxyvasicinone with (1S)-(+)- or (1R)-(-)-(10-camphorsulfonyl)oxaziridine (the Davis reagent), respectively. The aza-enolate anion of deoxyvasicinone was treated with (S)-(+)-reagent to afford (R)-(+)-vasicinone in 71% ee, while the reaction with (R)-(-)-reagent gave (S)-(-)-vasicinone in 62% ee. The optical purity was analyzed by HPLC on specially modified cellulose as a stationary phase. These results provided a facile method to prepare both optical isomers of vasicinone and confirmed the recently reversed stereochemistry of natural (-)-vasicinone.     

Asymmetric Cyclopropanation of Optically Active Vinyl Sulfoxides: A New Synthetic Approach to Biologically Active Compounds

Abstract

The influence of adjacent substituents on stereochemical course of cyclopropanation of vinyl sulfoxides with stabilized and nonstabilized ylides, as well as dependence on reaction conditions, was investigated. Application of optically active cyclopropanes obtained in the synthesis of conformationally constrained analogs of L-glutamic acid, the useful pharmacological tools in investigation of excitatory amino acid receptors, is presented.     

Asymmetric Hydrogenation of Vinylthioethers: Access to Optically Active 1,5‐Benzothiazepine Derivatives

A novel asymmetric hydrogenation of vinylthioethers was developed using a ruthenium(II) NHC complex. This method provides an efficient approach to optically active 1,5‐benzothiazepines featuring stereocenters with C?S bonds. Excellent enantioselectivities (up to 95 % ee) and high yields (up to 99 %) were obtained for a variety of substrates bearing a range of useful functional groups. Moreover, this methodology could be directly applied to the synthesis of the antidepressant drug R‐(?)‐thiazesim.     

手性配体催化二烷基锌—羰基不对称加成制光活性醇的反应

关于手性配体催化二烷基锌一羰基的不对称加成生成光活性醇的反应,从催化剂、不对称催化机理与自催化过程、手性放大等方面进行了概述,参考文献50篇。     

Unexpected cis-Selective 1,4-Addition Reaction of Lower Order Cyanocuprates to Optically Active 5-(tert-Butyldimethylsiloxy)-2-cyclohexenone

A remarkable cis selectivity has been observed in the 1,4-addition of lower order primary and secondary alkylcyanocuprates to 5-silyloxy- and 5-benzyloxy-substituted cyclohexenones. This enables the preparation of both enantiomers of the corresponding 5-alkyl-substituted cyclohexenones (S)- and (R)- 3 by the reaction of the readily available 5-(tert-butyldimethylsiloxy)-2-cyclohexenone ( 1 ) with either the lower or higher order cyanocuprate. DBU=1,8-diazabicyclo[5.4.0]undec-7-ene.     

A Highly Efficient Synthesis of Optically Active Ferrocenylethylamines via Hydride Reduction of Chiral Ferrocenylketimines

Due to using (R)‐ or (S)‐α‐methylbenzylamine as a chiral auxiliary, and low‐temperature regime for reduction of the intermediate ferrocenyl‐mono‐ or 1,1′‐bis‐ketimines, the corresponding secondary mono‐ or 1,1′‐bis‐amines were prepared with high diastereoselectivity. Removal of the α‐methylbenzyl group afforded the optically active primary mono‐ and bis‐ferrocenylethylamines in high yields. The absolute configuration of (R,R)‐ 3a and (S,S)‐ 3b was determined by X‐ray single crystal diffraction.     

Novel Chiral Aminophosphine Ligand:Synthesis and Application in Saymmetric Catalytic Hydrogenation Reaction

A new chiral aminophosphine ligand 6,6′-dimethoxy-2,2′-bis(diphenylphosphinoamino)biphenyl(DMBDPPABP) was prepared and its rhodium complex was found to be an effective catalyst for the asymmetric hydrogenation of amidoacrylic acid and its dervatives.The effects of solvent and reaction temperature on enantioselectivity were also studied.     

Novel Chiral Aminophosphine Ligand: Synthesis and Application in Asymmetric Catalytic Hydrogenation Reaction

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A Stereocontrolied Entry to Racemic Eremophilane and Valencane Sesquiterpenes via an Intramolecular Diels-Alder Reaction

A stereocontrolied route to racemic eremophilane and valencane sesquiterpenes is described via a common intermediate 15 , accessible from an intramolecular Diels-Alder reaction. ¹³ C - NMR .-shift assignments of the bicyclic intermediates and products are presented.     

Dual Asymmetric Induction in the Addition Reaction of Chiral Phosphites to C = N Compounds

Russian Journal of General Chemistry -     

A Total Synthesis of α-Kainic Acid by an Intramolecular Ene Reaction. Preliminary communication

The neurotoxin α-kainic acid ( 7 ) was synthesized from 1 via the thermal key step 5 → 6 in 41% overall yield.     

Ene Reaction with Pummerer-Type Reaction Intermediate of 1-[(2-Methylthio)ethanoyl]pyrrolidine: A Novel Synthesis of Trichonine

Pummerer-type reaction intermediate 2 of 1-[(2-methylthio)ethanoyl]pyrrolidine (1) has been found to react with 1-alkenes to afford ene adducts 3 . Trichonine 4 was synthesized from the adduct 3g .     

Biocatalytic Synthesis of Optically Active Hydroxyesters via Lipase-Catalyzed Decarboxylative Aldol Reaction and Kinetic Resolution

A two-step sequential biocatalytic process for the synthesis of chiral hydroxyesters that combines a lipase-catalyzed decarboxylative aldol reaction followed by kinetic resolution has been developed. The excellent combination of conventional and unconventional functions provides an attractive route for expanding the applications of biocatalysis.