Synthesis of C-glycopyranosylphloroacetophenone derivatives and their anomerization facilitated by 1,3-diaxial interactions.
The reaction of 2,3,4-tri-O-benzyl-6-deoxy-alpha-D-glucopyranosyl fluoride, 2,3,4,6-tetra-O-benzyl-alpha-D-allopyranosyl fluoride, and 2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl fluoride with 2,4-di-O-benzylphloroacetophenone, in the presence of boron trifluoride diethyl etherate, afforded, respectively, the corresponding 3-C-beta-D-glycopyranosylphloroacetophenone derivatives exclusively in anomerically pure form. Alternatively, the reaction of 2,3,4,6-tetra-O-benzyl-alpha-D-gulopyranosyl fluoride with 2,4-di-O-benzylphloroacetophenone afforded both the 3-C-beta-D-gulopyranosylphloroacetophenone derivative (4C(1) conformation) as the major product and the 3-C-alpha-D-gulopyranosylphloroacetophenone derivative (1C(4) conformation) as the minor product under identical conditions. Including the previously prepared C-glycosylphloroacetophenone derivatives that contain 3-C-beta-D-glucosyl, 3-C-beta-D-xylosyl, 3-C-beta-2-deoxy-D-arabino-hexosyl, 3-C-beta-D-galactosyl, 3-C-beta-L-arabinosyl, and 3-C-alpha-L-arabinosyl moieties, the conformation is dictated primarily by the preference of the bulky aromatic aglycon to orient equatorially, due to the strong repulsion of the aglycon. The anomerization is directed secondarily by the presence of 1,3-diaxial interactions in the sugar moiety.
Kumazawa
Toshihiro
T
Department of Chemistry and Chemical Engineering, Faculty of Engineering, Yamagata University, Jonan 4-3-16, Yonezawa, Japan.
Onda
Kanako
K
Okuyama
Hayato
H
Matsuba
Shigeru
S
Sato
Shingo
S
Onodera
Jun-ichi
J
D000098:Acetophenones / Q000138:chemical synthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy
D000098:Acetophenones; C476483:C-glycopyranosylphloroacetophenone