Chemistry Reference
In-Depth Information
O
O
CH
3
NCH
3
N
O
O
O
HN
O
O
N
O
NH
O
N
H
N
NH
2
O
O
NCH
3
O
CH
3
N
O
O
O
O
41
Actinomycin D
N
O
NH
2
O
NH
2
O
H
N
HO
O
NH
2
NH
NN
HN
N
S
H
2
N
O
N
O
H
N
N
S
H
O
O
O
NH
OH
HO
O
OH
O
OH
HO
R
SMe
2
+
OH
42
Bleomycin A2; R = OCONH
2
Figure 13.11
Structures of actinomycin D and bleomycin A2.
structures of the related esperamicins were published simultaneously (78, 79).
Calicheamicin is one of the most potent biologically active natural products ever
discovered. It causes single-stranded and double-stranded DNA cleavage through
a unique mechanism that involves reductive cleavage of the trisulfide “trigger”
followed by Bergman cyclization to a diradical. It proved to be too potent and
