NSC676794 Olean-12-en-28-oic acid, 3-.beta.-(6-methyl-.beta.-D-glucopyranuronosyloxy)-, [2-O-[3-O-(D-.apio.-.beta.-D-ribofuranosy)- 4-O-(.beta.-D-xylopyranosyl)-6-deoxy- .beta.-D-gulopyranosyl]-.beta.-D-xylopyranosyl] ester