Synthesis of pyrimidine 3'-allyl-2',3'-dideoxyribonucleosides by free-radical coupling

1989 ◽  
Vol 54 (11) ◽  
pp. 2767-2769 ◽  
Author(s):  
Chung K. Chu ◽  
B. Doboszewski ◽  
Walter Schmidt ◽  
Giliyar V. Ullas ◽  
Patrick Van Roey
Keyword(s):  
Free Radical ◽  
Radical Coupling

Evaluating the Effect of Termination by Chain - Chain Coupling in Living Free-Radical Polymerizations

2003 ◽  
Vol 56 (8) ◽  
pp. 775 ◽  
Author(s):  
Jeffrey Pyun ◽  
Ian Rees ◽  
Jean M. J. Fréchet ◽  
Craig J. Hawker
Keyword(s):  
Free Radical ◽  
Star Polymers ◽  
Star Polymer ◽  
Direct Result ◽  
Vinyl Monomers ◽  
Linear Polymers ◽  
Radical Coupling ◽  
Novel Approach ◽  
Vis Spectroscopy ◽  
Radical Polymerizations

A novel approach based on the reaction of multifunctional star polymers with chromophore-labelled linear polymers is presented for evaluating the extent of termination by chain–chain coupling during living free-radical polymerizations. A mixed initiating system consisting of an unlabelled, multifunctional initiator and an excess of a monofunctional alkoxyamine initiator containing a chromophore, such as pyrene, is used to initiate the living polymerization of vinyl monomers leading to a mixture of star and linear polymers. The occurrence of chain–chain coupling is readily identified and quantified by isolating the star polymer that is obtained and elucidating the level of incorporation of pyrene units by UV/vis spectroscopy. This allows the level of chain–chain coupling to be determined since the inclusion of pyrene into the star structure is a direct result of termination by radical coupling.

A non-enzymatic synthesis of (S)-(−)-rosmarinic acid and a study of a biomimetic route to (+)-rabdosiin

1997 ◽  
Vol 75 (12) ◽  
pp. 1783-1794 ◽  
Author(s):  
David E. Bogucki ◽  
James L. Charlton
Keyword(s):  
Lactic Acid ◽  
Free Radical ◽  
Caffeic Acid ◽  
Oxidative Coupling ◽  
Enzymatic Synthesis ◽  
Rosmarinic Acid ◽  
Radical Coupling ◽  
Preliminary Study

The synthesis of (S)-(−)-rosmarinic acid (30) in 9% overall yield is described. The synthesis was achieved by a convergent route in which 3-(3′,4′-dihydroxyphenyl)-(S)-lactic acid (23) and caffeic acid (25), both appropriately protected, were coupled to produce a pentaallyl precursor 29, which was then deprotected to give (S)-(−)-rosmarinic acid (30). A triallyl derivative 35 was similarly prepared and converted to (+)-rabdosiin (41) and its (1R,2S) isomer (42) via a biomimetic oxidative free radical coupling–cyclization followed by deallylation. The coupling–cyclization gave a ratio of rabdosiin diastereomers unlike that found in nature. A preliminary study showed that methyl (R)-mandelyl sinapate (15) could be dimerized diastereoselectively to give a 1,2-trans thomasidioate diester (16). Keywords: rabdosiin, rosmarinic acid, lignan, oxidative coupling.

Star Polymers of Sodium Styrenesulfonate Prepared by One-Pot TEMPO-Controlled SFRP

2012 ◽  
Vol 65 (8) ◽  
pp. 1117 ◽  
Author(s):  
Jianfu Ding ◽  
Steven Holdcroft
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Radical Polymerization ◽  
Star Polymers ◽  
One Pot ◽  
Stable Free Radical ◽  
Radical Coupling ◽  
Repeat Units ◽  
Divinyl Benzene ◽  
Sodium Styrenesulfonate

Star polymers of sodium styrenesulfonate with controlled arm length were prepared in a one-pot polymerization. Sodium styrenesulfonate was first polymerized with controlled molecular weight and narrow polydispersity by stable free radical polymerization. Poly(sodium styrenesulfonate) was terminated with divinyl benzene and star polymers prepared via stable free radical coupling of vinylic terminal groups. Star polymers based on arms of 20 and 32 repeat units possessed ~33 and ~41 arms per star respectively. Formation of star polymers with much longer arms was limited by poor coupling kinetics.

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