TY - JOUR T1 - Chiral 2-C-methylene glycosides and carbohydrate-derived pyrano[2,3-b][1]benzopyrans: synthesis via InCl3 catalyzed stereoselective ferrier rearrangement of 2-C-acetoxymethyl glycal derivatives JF - Tetrahedron Letters Y1 - 2005 A1 - Ghosh, R. A1 - Chakraborty, A. A1 - Maiti, D. K. A1 - Puranik, Vedavati G. KW - 2-C-methylene glycoside KW - InCl3 KW - pyranobenzopyran KW - Stereoselective AB -

2-C-Acetoxymethyl glycal derivatives react with aliphatic alcohols in the presence of InCl3 (30 mol %) to furnish the corresponding 2-C-methylene glycosides in excellent yields and with exclusive alpha-selectivity except for the methyl 2-C-methylene glycosides, which are formed in similar to 2:1 anomeric ratio in favour of the alpha-anomer. The reaction of 2-C-acetoxyglycals with phenols, however, produces the corresponding chiral carbohydrate-derived pyranobenzopyran derivatives via initial Ferrier rearrangement followed by tandem cyclization in excellent yields and moderate to high stereoselectivities in favour of the corresponding 10a-R-pyrano[2,3-b][1]benzopyran derivatives. (c) 2005 Elsevier Ltd. All rights reserved.

PB - PERGAMON-ELSEVIER SCIENCE LTD CY - THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND VL - 46 IS - 46 U3 -

Foreign

U4 -

2.347

ER -