Structural revisions of blumenol C glucoside and byzantionoside B.

The absolute stereochemistry of blumenol C glucoside and byzantionoside B was revised here as (6R,9S)- and (6R,9R)-9-hydroxymegastigman-4-en-3-one 9-O-beta-D-glucopyranosides, respectively, by modified Mosher's method. The empirical rules of (13)C-NMR chemical shift to determine the absolute stereochemistry of C-9 of 9-hydroxymegastigmane 9-O-beta-D-glucopyranoside were also discussed.