Plate 1 Spongia officinalis,
Greece. Photograph
courtesy E. Voultsiadou
et al., Creative Commons
2.5
25
O
O
O
O
OH
O
O
OH
O
O
O
HO
O
26
27
28
OH
O O
O O
OH
O
O
O
O
O
O
O
HO
O
O
O
O
O
Fig. 21 Structures of 25–
28. The furan ring moieties
are shown in red circles. The
other functional groups,
generated by oxidation,
reduction, and methyl ester
formation, are shown in
blue, orange, and purple,
respectively
OH
O
OH
H +
oxidation
furan ring moiety
O
O
H
HO
Fig. 20 Another pathway
for the formation of the
furan moiety
14
T. Mitsuhashi and I. Abe