125
Structurally, the compounds N
α
-Dimethyl neocoprogen I (13) and N
α
-Dimethyl
isoneocoprogen I (14) are similar to isoneocoprogen I (ferric triornicin) (9) and
neocoprogen I (10), respectively, except that they possess N
α
-dimethyl groups
instead of the N
α
-acetyl group. These compounds contain an N
δ
-anhydromevalonoyl
group at one end of the molecule and an N
δ
-acetyl group at the other end. In N
α
-
dimethyl neocoprogen I (13), the N
δ
-acetyl group is at the diketopiperazine end,
while in N
α
-dimethyl isoneocoprogen I (14), this group is in the ester-linked ornithyl
residue (Jalal et al. 1988).
Structures of three hydroxycoprogens 6–8 are hydroxyl analogues of 4, 9 and 10,
respectively, in which one of the terminal trans-anhydromevalonic acid residues is
replaced by trans-4,5-dihydroxy-3-methyl-2-pentenoic acid residues (Jalal and
Helm 1989).
R
N
OH
O
NH
HN
O
O
N
R
O
OH
2 R = CH 3
3 R =
CH 3
OH
Fig. 8.5 The structures of
dihydroxamate coprogens
Fig. 8.6 Coprogen (4) and its Fe
3+ ion complex
8 Chemistry and Biomedical Applications of Fungal Siderophores