Direct umpolung of glycals and related 2,3-unsaturated N-acetylneuraminic acid derivatives using samarium diiodide.
The umpolung of glycals with samarium diiodide offers a simple route to novel carbohydrate-derived nucleophilic reagents in a single step using a readily available reductant. The corresponding allyl samarium reagent that arises from the hexose series reacts with ketones at the C3 position with high stereoselectivity; carbon-carbon bond formation takes place only anti to the substituent at the C4 position of the dihydropyran ring. For the sialic acid series, the completely regio- and stereoselective coupling process of the samarium reagent occurs at the anomeric carbon atom and provides a new approach to the α-C-glycosides of N-acetyl neuraminic acid.
Université Paris-Sud and CNRS, Laboratoire de Synthèse de Biomolécules, Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182, 91405 Orsay (France); Department of Chemical Engineering, HCMC University of Technology, VNU-HCM, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City (Vietnam).
Tien Xuan
TX
Le
Caroline
C
Papin
Gilles
G
Doisneau
Jean-Marie
JM
Beau
D007454:Iodides / Q000737:chemistry*; D015394:Molecular Structure; D012493:Samarium / Q000737:chemistry*; D012794:Sialic Acids / Q000737:chemistry*
D007454:Iodides; D012794:Sialic Acids; D012493:Samarium; C409809:samarium diiodide
carbohydrates; reductive coupling; samarium; sialic acids; umpolung