The 4,6-O-[alpha-(2-(2- iodophenyl)ethylthiocarbonyl)benzylidene] protecting group: stereoselective glycosylation, reductive radical fragmentation, and synthesis of beta-D-rhamnopyranosides and other deoxy sugars.
[reaction: see text] In the thioglycoside/BSP/Tf(2)O glycosylation method, the 4,6-O-[alpha-(2-(2-iodophenyl)ethylthiocarbonyl)benzylidene] group enforces beta-selectivity in mannopyranosylations. Following glycosylation, treatment with Bu(3)SnH in toluene at reflux affords regioselective, reductive fragmentation to the 6-deoxy-beta-mannosides (beta-rhamnosides). Applied to glucosides, the radical fragmentation provides 6-deoxyglucosides, whereas 4-deoxygalactosides are the preferred products in the galactose series. The radical fragmentation is fully compatible with the presence of benzyl and p-methoxybenzyl ethers and with acetate esters
Crich
David
D
Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061, USA. dcrich@uic.edu
Yao
Qingjia
Q
D001597:Benzylidene Compounds / Q000737:chemistry*; D003837:Deoxy Sugars / Q000138:chemical synthesis*; D006031:Glycosylation; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry; D012210:Rhamnose / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D013237:Stereoisomerism; D013865:Thioglycosides / Q000737:chemistry
D001597:Benzylidene Compounds; D003837:Deoxy Sugars; D011714:Pyrans; D013865:Thioglycosides; D012210:Rhamnose