scholarly journals Synthesis of Optically Pure (+)-Puraquinonic Acid and Assignment of Absolute Configuration to Natural (-)-Puraquinonic Acid. Use of Radical Cyclization for Asymmetric Generation of a Quaternary Center.

ChemInform ◽  
2004 ◽  
Vol 35 (44) ◽  
Author(s):  
Derrick L. J. Clive ◽  
Maolin Yu ◽  
Mousumi Sannigrahi
Keyword(s):  
Absolute Configuration ◽  
Radical Cyclization ◽  
Quaternary Center ◽  
Puraquinonic Acid ◽  
Optically Pure

Synthesis and resolution of an asymmetric arsonium cation. Crystal and molecular structures of (R)-Benzyl(methyl)(4-methylphenyl)(naphthalen-1-yl)- arsonium bromide and hexafluorophosphate

1984 ◽  
Vol 37 (6) ◽  
pp. 1171 ◽  
Author(s):  
DG Allen ◽  
CL Raston ◽  
BW Skelton ◽  
AH White ◽  
SB Wild
Keyword(s):  
Ion Exchange ◽  
Absolute Configuration ◽  
Optically Active ◽  
Molecular Structures ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Ion Exchange Column ◽  
Optically Pure

The (�)-benzyl(methyl)(4-methylphenyl)(naphthalen-1-yl)arsonium cation has been synthesized and subsequently resolved by fractional crystallization of monohydrogen [R-(R*,R*)]-2,3-bis(benzoyloxy)- butanedioate salts. The separated diastereoisomers were converted into the corresponding optically active arsonium bromides by ion-exchange column chromatography. The absolute configuration of the arsonium cation exhibiting a positive rotation at 589 nm (sodium D line) has been established as (R) by single-crystal X-ray analysis of both the bromide and hexafluorophosphate salts. The arsonium bromide with [α]D + 54.8�(c, 0.62 in CH2Cl2) crystallizes in the orthorhombic space group P212121 (D24, No.19) with a 22.472(8), b 15.724(7), c 12.585(5) � and U 4447(3) �3. The corresponding hexafluorophosphate with [α]D + 19.3� (c, 0.5 in CH2Cl2) crystallizes in the same space group with a 23.56(2), b 16.40(1), c 13.12(1) � and U 5067(6) � 3. Benzylidene transfer to benzaldehyde from the arsonium ylide derived from either of the arsonium salts produced optically pure (–)-(S)-methyl(4-methylphenyl)(naphthalen-1-yl)arsine, [α]D - 115.9� (c, 0.593 in CHCl3), and partly resolved [R-(R*,R*)]-2,3-diphenyloxiran.

scholarly journals Expedient Access to Enantiopure Cyclopentanic Natural Products: Total Synthesis of (-)-Cyclonerodiol

2015 ◽  
Vol 10 (1) ◽  
pp. 1934578X1501000
Author(s):  
Carmen Pérez Morales ◽  
M. Mar Herrador ◽  
José F. Quílez del Moral ◽  
Alejandro F. Barrero
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
Radical Cyclization ◽  
Formal Synthesis ◽  
Common Precursor ◽  
Enantiospecific Synthesis ◽  
Optically Pure

Following the principles of collective total synthesis, a number of natural products sharing an optically pure, multifunctional, cyclopentanic core were synthesized from a common precursor: plinol A (1). This intermediate was efficiently obtained in only four steps from (-)-linalool (2) using as the key step a Ti(III)-mediated diastereoselective radical cyclization. The feasibility of this approach was confirmed with the expedient enantiospecific synthesis of cyclonerodiol (3), and the formal synthesis of chocol G (4) and piperitone (5).

Enantioselective Arylation of 3-Carboxamide Oxindoles with Quinone Monoimines and Synthesis of Chiral Spirooxindole-benzofuranones

Synlett ◽  
2019 ◽  
Vol 30 (09) ◽  
pp. 1067-1072
Author(s):  
Hui Chen ◽  
Hui Liu ◽  
Si-Han Zhao ◽  
Shao-Bing Cheng ◽  
Xiao-Ying Xu ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Absolute Configuration ◽  
Tertiary Amine ◽  
The Other ◽  
X Ray ◽  
Quaternary Center ◽  
Crystal Structural ◽  
The Absolute

A highly enantioselective arylation of 3-carboxamide oxoindoles with quinone monoimines is described. Various 3-aryl-3-carboxamide oxindoles with an all-carbon quaternary center were obtained in moderate to good yields (up to 99%) with moderate to good enantioselectivities (up to 98%) in the presence of a bifunctional thiourea-tertiary amine catalyst. The absolute configuration of one product was determined by an X-ray crystal structural analysis and the absolute configurations of the other products can be assigned by analogy. Moreover, several chiral spirooxindole-benzofuranones were synthesized from the 3-aryl-3-carboxamide oxindoles in moderate yields with moderate to good enantioselectivities.

Stereoselective Quaternary Center Construction via Atom-Transfer Radical Cyclization Using Silicon Tethers on Acyclic Precursors

2009 ◽  
Vol 11 (14) ◽  
pp. 3148-3151 ◽  
Author(s):  
Martin Duplessis ◽  
Marie-Eve Waltz ◽  
Mohammed Bencheqroun ◽  
Benoit Cardinal-David ◽  
Yvan Guindon
Keyword(s):  
Radical Cyclization ◽  
Atom Transfer ◽  
Quaternary Center ◽  
Silicon Tethers ◽  
Atom Transfer Radical Cyclization

Synthesis of polyquinanes via bicyclo [2.1.0] pentane intermediates. An easy access to optically pure diquinane alcohols of known absolute configuration.

1993 ◽  
Vol 4 (12) ◽  
pp. 2475-2482 ◽  
Author(s):  
Michel Franck-Neumann ◽  
Michel Miesch ◽  
Alain Cotté ◽  
Laurence Gross ◽  
Bernard Metz
Keyword(s):  
Absolute Configuration ◽  
Easy Access ◽  
Optically Pure
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