Synthesis of C-mannopyranosylphloroacetophenone derivatives and their anomerization.
The reaction of 2,3,4-tri-O-benzyl-alpha-L-rhamnopyranosyl fluoride (6-deoxy-2,3,4-tri-O-benzyl-alpha-L-mannopyranosyl fluoride) with 2,4-dibenzylphloroacetophenone, in the presence of boron trifluoride.diethyl etherate, afforded both the 3-C-alpha-L- and the 3-C-beta-L-rhamnopyranosylphloroacetophenone derivatives. The 3-C-alpha-L-rhamnoside was produced as a major product, while the 3-C-beta-L-rhamnoside was produced as a minor product via anomerization of the 3-C-alpha-L-rhamnoside. Alternatively, the reaction of 2,3,4,6-tetra-O-benzyl-alpha-D-mannopyranosyl fluoride with 2,4-dibenzylphloroacetophenone afforded both the 3-C-alpha-D- and the 3-C-beta-D-mannnopyranosylphloroacetophenone derivatives under identical conditions. The 3-C-beta-D-mannoside was produced as a major product via anomerization of the 3-C-alpha-D-mannoside during the reaction. These differences in composition result apparently from the magnitude of the 1,3-diaxial interactions between the C-3 and C-5 positions in these sugar moieties.
Kumazawa
T
T
Department of Chemistry and Chemical Engineering, Faculty of Engineering, Yamagata University, Yonezawa, Japan. tk111@dip.yz.yamagata-u.ac.jp
Sato
S
S
Matsuba
S
S
Onodera
J I
JI
D000098:Acetophenones / Q000138:chemical synthesis*; D005419:Flavonoids / Q000138:chemical synthesis; D008358:Mannose / Q000031:analogs & derivatives* / Q000138:chemical synthesis*
D000098:Acetophenones; D005419:Flavonoids; D008358:Mannose