The 1H and 13C NMR spectral features of 1 were in good
agreement with those reported for jasuroside A (10), which
had been isolated from J. urophyllum by Shen et al.,6
except for the assignments of H-2¢¢ and H-3¢¢. The absolute
stereochemistry of 10 was deduced solely using its NOESY
spectrum. This prompted us to establish the absolute
stereochemistry of 1 by chemical evidence. To determine
the absolute configuration at C-5¢¢ in triol 9 by a modification
of Mosher’s method,7 its (R)- and (S)-MTPA esters
(11,12) were prepared. The NOESY experiments with 12
confirmed the relative configurations at C-1¢¢, C-2¢¢, C-3¢¢
and C-5¢¢ (Figure 1). The ¢ä values of the MTPA derivatives
determined the absolute configuration of C-5¢¢ to be S,
indicating 9 to be the 5¢¢-epimer of triol 6. This was