The presence
of a carbamate moiety was suggested by an IR
band at 1650 cm-1, a signal at ä 154.7 in the 13C NMR
spectrum,20 and a mass fragment at m/z 341 [M - (CH2-
N-COOCH3) + H]+. The 1H and 13C NMR spectra of 3 were
similar to those of 2 except for the presence of a methoxy
signal, indicated by signals at ä 3.90 in 1H NMR and ä 59.8
in 13C NMR. Significant correlated sequences of OMe-3/
OMe-2/OMe-1/H-11/OMe-10/OMe-9/H-8/H-7/H-6a and H-4/
H-5 were observed in the NOESY spectrum (Figure 1),
confirming the positions of the methoxy groups. Thus, the
structure of 3 was determined as illustrated and named
romucosine G (3). Treatment of (+)-norpurpureine with
triethylamine and methyl chlorocarbonate gave a compound
whose mp, UV, TLC, and 1H NMR data were the
same as those of 3.