Chemistry Reference
In-Depth Information
bottromycins [10-12] and coformycin [13,14] has been reported from Strepromyces sp.
Other amidines were isolated from fungi, marine invertebrates and plants.
10.2.1 Natural Amidines from Microorganisms and Fungi
10.2.1.1 Birnbaumins
Bartsch et al. reported the isolation of birnbaumins A and B (1-2), unusual 1-hydroxyindole
pigments from fungus, the
Leucocoprinus birnbaumii (Corda) Singer
[15]. The structure of birnbaumin A (1) consisted of 1-hydroxyindoleglyoxyl amide with a
side chain containing a very rare N-hydroxybisamidine moiety, which was determined by
the permethylation with diazomethane and the comparison of spectral data with the
calculated value of another structural candidate (Figure 10.1).
flower pot parasol
10.2.1.2
Efrapeptins and Neoefrapeptins
Efrapeptins are a complex mixture of peptide antibiotics produced by the fungus Tolypo-
cladium niveum (syn. Tolypocladium inflatum, Beauveria nivea), a soil hyphomycete. The
peptides are inhibitors of mitochondrial oxidative phosphorylation and ATPase activity and
photophosphorylation in chloroplasts. The structure of efrapeptin D was first proposed by
Bullough [16] as polypeptides composed of 15 amino acid residues including a large
number of
-alanine and
L
-isovaline
(Iva) with an uncharacterized C-terminal group (X), which consisted of a basic part with
leucine residue. Gupta et al. [17] reported the full characterization of efrapeptin C (3) and
the derivatives D (4)-G based on 2D-NMR analysis and mass fragmentation. They showed
that the C-terminal group contains the bicyclic amidine ring, the same structure as that of the
versatile artificial bicyclic amidine 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) (Figure 10.2
for efrapeptin D; Table 10.1). Efrapeptins C (3) and E (5) showed insect toxicity against
beetle Leptinotarsa decemlineata (Coleoptera) (LC
50
at 18.9 and 8.4 ppm, respectively).
Efrapeptins C-G showed mitochondrial ATPase inhibitory activity against fungi (Metar-
hizium anisopliae and T. niveum) and insect (flight muscles from Musca domstica).
Recently, Fredenhagen et al. [18] reported the isolation of neoefrapeptins A (6)toN
from the culture broth of the strain SID 22 780, identified as Geotrichum candidum Link:F.
The structures were very similar to those of efrapeptins, which contain a bicyclic amidine
part at the C-terminus and Aib, Iva and Pip, as well as other unnatural amino acids such as
3-methylproline (3M-Pro) and 1-aminocyclopropanecarboxylic acid (Acc).
a
-aminoisobutyric acid (Aib), pipecolic acid (Pip),
b
O
NH
OH
N
N
birnbaumin A (
1
): R = H
birnbaumin B (
2
): R = OH
H
O
NH
2
N
OH
R
Figure 10.1
Structures of birnbaumins A-B (1-2)
