Chemistry Reference
In-Depth Information
SCHEME 19.1
enediynes are chromoproteins, being formed by a complex between a
protein and an unstable chromophore containing the enediyne moiety.
Probably, another four natural chromoproteins (largomycin, sporamycin,
actinoxanthin, and auromomycin) belong to the type III family, but their
structure has not been yet elucidated. Scheme 19.1 shows the structure of the
chromophores of lidamycin and neocarzinostatin, as examples of type II
and type III enediynes. In this chapter we will, however, discuss mainly of
type I natural enediynes and their artificial analogs.
19.1.2 T
HE
N
ATURAL
E
NEDIYNES OF
T
YPE
I
Calicheamicin
g
1
I
from Micromonospora echinospora
calichensis is the most prominent of the type I enediynes.
4,11
There are
currently about 15 different calicheamicins, characterized by small varia-
tions on the tetrasaccharide part. Apart from the enediyne moiety, these
molecules contain several unusual structural features, such as the acyl
enamine and the trisulfide in the aglycon, and the hexasubstituted aryl ring
and the thioester and hydroxylamine glycosidic linkages in the saccharide.
Namenamicin 2,
12
and the shishijimicins 3,
13
from the thin encrusting
orange ascidians Polysyncraton lithostrotum and Didemnum proliferum,have
the same aglycon, while in the esperamicins 4,
14
isolated from Actinomadura
verrucosospora, the aglycon is quite similar, having only an additional
hydroxy group. On the other hand, the saccharide portions of 2, 3, and
4 are much more different from that of 1. The last member of this
family, dynemicin 5
15,16
(
Scheme 19.2
)
from Michromonospora chersina, contains a novel
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