N-trichloroethoxycarbonyl-glucosamine derivatives as glycosyl donors.
D-Glucosamine can be readily transformed into 1,3,4,6-tetra-O-acetyl-2-deoxy-2-(2,2,2-trichloroethoxycarbonylamino+ ++) -D-glucopyranose (2). From this intermediate valuable glycosyl donors can be obtained; reaction with ethanethiol in the presence of boron trifluoride etherate afforded ethyl 3,4,6-tri-O-acetyl-2-deoxy-1-thio-2-(2,2, 2-trichloroethoxycarbonylamino)-beta-D-glucopyranoside (4) which gave, upon N-acetylation, the N-acetyl-N-trichloroethoxycarbonyl derivative (5). Selective removal of the 1-O-acetyl group in 2 followed by treatment with trichloroacetonitrile in the presence of base afforded 3,4,6-tri-O-acetyl-2-deoxy-2-(2,2,2-trichloroethoxycarbonylamino)- alpha -D-glucopyranosyl trichloroacetimidate (6). Reaction of 5 with five selectively protected glycosides as glycosyl acceptors in the presence of N-iodosuccinimide/trifluoromethanesulfonic acid as the promoter system furnished the corresponding beta-glycosides in good yields, thus exhibiting the valuable glycosyl donor properties of 5. Reductive removal of the trichloroethoxycarbonyl (Teoc) group afforded the corresponding N-acetyl-protected saccharides in high yields. The imidate 6 reacted with three of the above acceptors in the presence of catalytic amounts of trimethylsilyl trifluoromethanesulfonate to give the beta-linked disaccharides in even better yields. The direct replacement of the N-Teoc group by the N-acetyl group using zinc/acetic anhydride, via the free amines as transient intermediates, adds to the high efficiency and convenience of this methodology.
Dullenkopf
W
W
Fakultät für Chemie, Universität Konstanz, Germany.
Castro-Palomino
J C
JC
Manzoni
L
L
Schmidt
R R
RR
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D004187:Disaccharides / Q000138:chemical synthesis; D005944:Glucosamine / Q000031:analogs & derivatives* / Q000138:chemical synthesis*; D006027:Glycosides / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D014312:Trisaccharides / Q000138:chemical synthesis
D004187:Disaccharides; D006027:Glycosides; D014312:Trisaccharides; D005944:Glucosamine