Chemistry Reference
In-Depth Information
R
2
R
2
H
N
H
N
palau'amine (revised) (
26
): R
1
= R
2
= H
N
N
H
2
N
H
2
N
tetrabromostyloguanidine (
27
)
H
HO
N
O
H
HO
N
O
O
H
HN
12
H
D
HN
H
R
1
=
R
2
= Br
17
H
E
H
Br
HN
HN
H
HN
NH
2
Cl
NHR
1
Cl
Br
25
Figure 10.8
Structures of palau
amine (26) and tetrabromostyloguanidine (27)
10.3.2.2 Crambescins, Ptilomycalins and Batzelladines
Berlinck et al. reported the isolation of polycyclic guanidine alkaloids from the Mediterra-
nean marine sponge Crambe crambe. The series of these compounds was at first named as
crambins [69], later on renamedas crambescins [70].CrambescinsA(28), B(29) [69] andC1
(30) [70,71] possess a common framework containing the six-membered ring cyclic
guanidine, a long alkyl chain and an ester function with terminal guanidine group. Only
crambescin B possess a spiro bicyclic ring. The stereochemistry of crambescin B (29)was
revised by synthetic studies of model compounds [72]. Ptilocaulin (31) is a polycyclic
guanidine derivative isolated from the Carribean Batzella sp, wrongly identified as
Ptilocaulis spiculifer, and a red sponge Hemimycale sp. from the Red Sea [73]. From other
marine sponges, ptilomycalins (A, 32) [74,75] and crambescidin 800 (33) [75] have also
been isolated as a series of guanidine alkaloids (Figure 10.9).
BatzelladineA (34) and the derivatives B-E (35-38) are the first natural products of small
molecule weight that have been shown to inhibit the gp120-CD4 interaction [76]. On the
other hand, batzelladines F-I (39-42) induced a dissociation of a p56ck-CD4 binding
complex [77]. The structures of batzelladines A (34), D (37) [78] and F (39) [79] have been
revised (revised structures are shown in Figure 10.10). Recently, ptilomycalin D (43) [80],
batzelladines J (44) [81] and K-N (45-48) [82] have been isolated from sponges
Monanchona dianchora and M. unguifera, respectively (Figure 10.10). Total syntheses
of batzelladines were recently reported [79,83,84].
10.3.3 Natural Guanidines from Higher Plant
10.3.3.1 Martinelline and Martinellic Acid
Two pyrroloquinoline alkaloids, martinelline (49) and martinellic acid (50), have been
isolated from an organic extract of root of Martinella iquitosensis A. Sampaio (Bigno-
niaceae) by Witherup et al. (part of Merck
s research group) as bradykinin receptor
antagonists (Figure 10.11) [85]. The optical rotations of natural 49 and 50 were reported
as [
]
D
รพ
9.4 and
8.5, respectively, however the synthetic (
)
50 showed a considerably
a
larger value with the same sense ([
]
D
122.7; [86,87]
164.3 [88]). A compound with the
a
