摘要:
The spacer containing trimer 4-(aminoethyl)phenyl 2,4-di-O-Me-3-O-[2-O-methyl-3-O-(4-O-acetyl-2-O-methyl-alpha-L-fucopyranosyl)-alpha-L-rhamnopyranosyl]-alpha-L-rhamnopyranoside (2) was prepared by stepwise extension of 4-[2-(benzyloxycarbonyl-amino)ethyl]phenyl 2,4-di-O-methyl-alpha-L-rhamnopyranoside (19) with property protected ethyl thioglycosides of L-rhamnose 8 and L-fucose 12 or 16 using iodonium ions as promotors. The resulting trimers 22 or 23 were deblocked in two steps to give homogeneous 2. Alternatively, fully protected trimer 22 was assembled by iodonium ion assisted condensation of the phenyl 1-thio-alpha-L-rhamnopyranoside 29 with 12 followed by extension of dimer 31 with 19.