Under iron-depleted culture conditions, the entomopathogenic fungus Metarhizium robertsii (Bischoff, Humber, and Rehner) (= M. anisopliae) produces a complex of extracellular siderophores including novel O-glycosylated and N-oxidized coprogen-type compounds as well as the known fungal siderophores N(α)-dimethylcoprogen (NADC) and dimerumic acid (DA). Metachelin A (1), the most abundant component in the M. robertsii siderophore mixture, was characterized as a 1094 Da analogue of NADC that is O-glycosylated by β-mannose at both terminal hydroxyl groups and N-oxidized at the dimethylated α-nitrogen. The mixture also contained a 1078 Da analogue, metachelin B (2), which lacks the N-oxide modification. Also characterized were the aglycone of 1, i.e., the N-oxide of NADC (3), and the monomannoside of DA (6). N-Oxide and O-glycosyl substituents are unprecedented among microbial siderophores. At high ESIMS source energy and at room temperature in DMSO, 1 underwent Cope elimination, resulting in loss of the N(α)-dimethyl group and dehydration of the α-β bond. High-resolution ESIMS data confirmed that all tri- and dihydroxamate siderophores (1-6) complex with trivalent Fe, Al, and Ga. In a chrome azurol S assay, all of the M. robertsii siderophores showed iron-binding activity roughly equivalent to that of desferrioxamine B.

metachelin, iron-depleted culture conditions, Metarhizium robertsii, fungal siderophore

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6	C7	C8	C9	C10	C11	C12	C13	C14	C15	C16	C17	C18	C19	C20	C21	C22	C23	C24	C25	C26	C27	C28	C29	C30	C31	C32	C33	C34	C35
11	bDManp	101.8	72.6	75.4	68.7	78.5	63.0
22	bDManp	101.8	72.6	75.4	68.7	78.5	63.0
	Subst	170.5	55.8	32.5	23.7	48.5	169.9	117.9	152.7	41.7	68.3	19.3	170.6	55.8	32.5	23.7	48.5	169.4	119.1	150.6	40.3	64.7	18.6	168.6	80.9	26.3	24.4	47.8	169.9	117.5	153.4	41.7	68.3	19.3	57.5	54.9


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6	H7	H8	H9	H10	H11	H12	H13	H14	H15	H16	H17	H18	H19	H20	H21	H22	H23	H24	H25	H26	H27	H28	H29	H30	H31	H32	H33	H34	H35
11	bDManp	4.54	3.85	3.45	3.55	3.22	3.72-3.88
22	bDManp	4.54	3.85	3.45	3.55	3.22	3.72-3.88
	Subst	-	4.03	1.85	1.74	3.68	-	6.34	-	2.467	3.74-4.07	2.09	-	4.03	1.85	1.74	3.68	-	6.35	-	2.58	4.46	2.08	-	4.26	1.97-2.06	1.63-1.71	3.65-3.75	-	6.37	-	2.474	3.75-4.07	2.10	3.39	3.41


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6	C7/H7	C8/H8	C9/H9	C10/H10	C11/H11	C12/H12	C13/H13	C14/H14	C15/H15	C16/H16	C17/H17	C18/H18	C19/H19	C20/H20	C21/H21	C22/H22	C23/H23	C24/H24	C25/H25	C26/H26	C27/H27	C28/H28	C29/H29	C30/H30	C31/H31	C32/H32	C33/H33	C34/H34	C35/H35
11	bDManp	101.8/4.54	72.6/3.85	75.4/3.45	68.7/3.55	78.5/3.22	63.0/3.72-3.88
22	bDManp	101.8/4.54	72.6/3.85	75.4/3.45	68.7/3.55	78.5/3.22	63.0/3.72-3.88
	Subst		55.8/4.03	32.5/1.85	23.7/1.74	48.5/3.68		117.9/6.34		41.7/2.467	68.3/3.74-4.07	19.3/2.09		55.8/4.03	32.5/1.85	23.7/1.74	48.5/3.68		119.1/6.35		40.3/2.58	64.7/4.46	18.6/2.08		80.9/4.26	26.3/1.97-2.06	24.4/1.63-1.71	47.8/3.65-3.75		117.5/6.37		41.7/2.474	68.3/3.75-4.07	19.3/2.10	57.5/3.39	54.9/3.41

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

C/C(=C\C(=O)N(O)CCC[C@@H]1NC(=O)[C@H](CCCN(O)C(=O)/C=C(\C)CCO[C@@H]2O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]2O)NC1=O)CCOC(=O)[C@H](CCCN(O)C(=O)/C=C(\C)CCO[C@@H]1O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]1O)[N+](C)(C)[O-]

1095.16 g/mol (C₄₇H₇₈N₆O₂₃)

Under iron-depleted culture conditions, the entomopathogenic fungus Metarhizium robertsii (Bischoff, Humber, and Rehner) (= M. anisopliae) produces a complex of extracellular siderophores including novel O-glycosylated and N-oxidized coprogen-type compounds as well as the known fungal siderophores N(α)-dimethylcoprogen (NADC) and dimerumic acid (DA). Metachelin A (1), the most abundant component in the M. robertsii siderophore mixture, was characterized as a 1094 Da analogue of NADC that is O-glycosylated by β-mannose at both terminal hydroxyl groups and N-oxidized at the dimethylated α-nitrogen. The mixture also contained a 1078 Da analogue, metachelin B (2), which lacks the N-oxide modification. Also characterized were the aglycone of 1, i.e., the N-oxide of NADC (3), and the monomannoside of DA (6). N-Oxide and O-glycosyl substituents are unprecedented among microbial siderophores. At high ESIMS source energy and at room temperature in DMSO, 1 underwent Cope elimination, resulting in loss of the N(α)-dimethyl group and dehydration of the α-β bond. High-resolution ESIMS data confirmed that all tri- and dihydroxamate siderophores (1-6) complex with trivalent Fe, Al, and Ga. In a chrome azurol S assay, all of the M. robertsii siderophores showed iron-binding activity roughly equivalent to that of desferrioxamine B.

metachelin, iron-depleted culture conditions, Metarhizium robertsii, fungal siderophore

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

C/C(=C\C(=O)N(O)CCC[C@@H]1NC(=O)[C@H](CCCN(O)C(=O)/C=C(\C)CCO[C@@H]2O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]2O)NC1=O)CCOC(=O)/C=C/CCN(O)C(=O)/C=C(\C)CCO[C@@H]1O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]1O

1034.076 g/mol (C₄₅H₇₁N₅O₂₂)

Under iron-depleted culture conditions, the entomopathogenic fungus Metarhizium robertsii (Bischoff, Humber, and Rehner) (= M. anisopliae) produces a complex of extracellular siderophores including novel O-glycosylated and N-oxidized coprogen-type compounds as well as the known fungal siderophores N(α)-dimethylcoprogen (NADC) and dimerumic acid (DA). Metachelin A (1), the most abundant component in the M. robertsii siderophore mixture, was characterized as a 1094 Da analogue of NADC that is O-glycosylated by β-mannose at both terminal hydroxyl groups and N-oxidized at the dimethylated α-nitrogen. The mixture also contained a 1078 Da analogue, metachelin B (2), which lacks the N-oxide modification. Also characterized were the aglycone of 1, i.e., the N-oxide of NADC (3), and the monomannoside of DA (6). N-Oxide and O-glycosyl substituents are unprecedented among microbial siderophores. At high ESIMS source energy and at room temperature in DMSO, 1 underwent Cope elimination, resulting in loss of the N(α)-dimethyl group and dehydration of the α-β bond. High-resolution ESIMS data confirmed that all tri- and dihydroxamate siderophores (1-6) complex with trivalent Fe, Al, and Ga. In a chrome azurol S assay, all of the M. robertsii siderophores showed iron-binding activity roughly equivalent to that of desferrioxamine B.

metachelin, iron-depleted culture conditions, Metarhizium robertsii, fungal siderophore

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6	C7	C8	C9	C10	C11	C12	C13	C14	C15	C16	C17	C18	C19	C20	C21	C22	C23	C24	C25	C26	C27	C28	C29	C30	C31	C32	C33	C34	C35
11	bDManp	101.8	72.7	75.4	68.7	78.5	63.0
22	bDManp	101.8	72.7	75.4	68.7	78.5	63.0
	Subst	170.6	55.9	32.6	23.7	48.5	169.9	117.8	152.7	41.7	68.3	19.3	170.6	55.9	32.6	23.7	48.5	169.9	118.7	151.3	40.8	63.8	18.7	172.0	68.5	27.2	24.5	48.5	169.9	117.8	153.0	41.7	68.3	19.3	42.3	42.3


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6	H7	H8	H9	H10	H11	H12	H13	H14	H15	H16	H17	H18	H19	H20	H21	H22	H23	H24	H25	H26	H27	H28	H29	H30	H31	H32	H33	H34	H35
11	bDManp	4.54	3.85	3.45	3.55	3.22	3.72-3.88
22	bDManp	4.54	3.85	3.45	3.55	3.22	3.72-3.88
	Subst	-	4.02	1.84-1.85	1.76	3.68	-	6.33	-	2.47	3.75-4.07	2.09	-	4.02	1.84-1.85	1.76	3.68	-	6.33	-	2.55	4.39	2.10	-	3.52	1.80	1.72	3.68	-	6.33	-	2.47	3.75-4.07	2.09	2.53	2.53


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6	C7/H7	C8/H8	C9/H9	C10/H10	C11/H11	C12/H12	C13/H13	C14/H14	C15/H15	C16/H16	C17/H17	C18/H18	C19/H19	C20/H20	C21/H21	C22/H22	C23/H23	C24/H24	C25/H25	C26/H26	C27/H27	C28/H28	C29/H29	C30/H30	C31/H31	C32/H32	C33/H33	C34/H34	C35/H35
11	bDManp	101.8/4.54	72.7/3.85	75.4/3.45	68.7/3.55	78.5/3.22	63.0/3.72-3.88
22	bDManp	101.8/4.54	72.7/3.85	75.4/3.45	68.7/3.55	78.5/3.22	63.0/3.72-3.88
	Subst		55.9/4.02	32.6/1.84-1.85	23.7/1.76	48.5/3.68		117.8/6.33		41.7/2.47	68.3/3.75-4.07	19.3/2.09		55.9/4.02	32.6/1.84-1.85	23.7/1.76	48.5/3.68		118.7/6.33		40.8/2.55	63.8/4.39	18.7/2.10		68.5/3.52	27.2/1.80	24.5/1.72	48.5/3.68		117.8/6.33		41.7/2.47	68.3/3.75-4.07	19.3/2.09	42.3/2.53	42.3/2.53

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

C/C(=C\C(=O)N(O)CCC[C@@H]1NC(=O)[C@H](CCCN(O)C(=O)/C=C(\C)CCO[C@@H]2O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]2O)NC1=O)CCOC(=O)[C@H](CCCN(O)C(=O)/C=C(\C)CCO[C@@H]1O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]1O)N(C)C

1079.161 g/mol (C₄₇H₇₈N₆O₂₂)

Under iron-depleted culture conditions, the entomopathogenic fungus Metarhizium robertsii (Bischoff, Humber, and Rehner) (= M. anisopliae) produces a complex of extracellular siderophores including novel O-glycosylated and N-oxidized coprogen-type compounds as well as the known fungal siderophores N(α)-dimethylcoprogen (NADC) and dimerumic acid (DA). Metachelin A (1), the most abundant component in the M. robertsii siderophore mixture, was characterized as a 1094 Da analogue of NADC that is O-glycosylated by β-mannose at both terminal hydroxyl groups and N-oxidized at the dimethylated α-nitrogen. The mixture also contained a 1078 Da analogue, metachelin B (2), which lacks the N-oxide modification. Also characterized were the aglycone of 1, i.e., the N-oxide of NADC (3), and the monomannoside of DA (6). N-Oxide and O-glycosyl substituents are unprecedented among microbial siderophores. At high ESIMS source energy and at room temperature in DMSO, 1 underwent Cope elimination, resulting in loss of the N(α)-dimethyl group and dehydration of the α-β bond. High-resolution ESIMS data confirmed that all tri- and dihydroxamate siderophores (1-6) complex with trivalent Fe, Al, and Ga. In a chrome azurol S assay, all of the M. robertsii siderophores showed iron-binding activity roughly equivalent to that of desferrioxamine B.

metachelin, iron-depleted culture conditions, Metarhizium robertsii, fungal siderophore

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6	C7	C8	C9	C10	C11	C12	C13	C14	C15	C16	C17	C18	C19	C20	C21	C22
11	bDManp	101.8	72.7	75.4	68.7	78.5	63.0
	Subst	170.5	54.8	31.4	22.4	48.1	170.0	117.1	151.8	42.8	67.7	18.5	170.5	54.8	31.4	22.4	48.1	170.0	117.2	152.2	39.9	59.9	18.5


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6	H7	H8	H9	H10	H11	H12	H13	H14	H15	H16	H17	H18	H19	H20	H21	H22
11	bDManp	4.67	3.96	3.62	3.56	3.36	3.72-3.93
	Subst	-	4.18	1.81-1.88	1.70-1.75	3.70	-	6.21	-	2.48	3.82-4.05	1.97	-	4.18	1.81-1.88	1.70-1.75	3.70	-	6.19	-	2.41	3.76	1.97


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6	C7/H7	C8/H8	C9/H9	C10/H10	C11/H11	C12/H12	C13/H13	C14/H14	C15/H15	C16/H16	C17/H17	C18/H18	C19/H19	C20/H20	C21/H21	C22/H22
11	bDManp	101.8/4.67	72.7/3.96	75.4/3.62	68.7/3.56	78.5/3.36	63.0/3.72-3.93
	Subst		54.8/4.18	31.4/1.81-1.88	22.4/1.70-1.75	48.1/3.70		117.1/6.21		42.8/2.48	67.7/3.82-4.05	18.5/1.97		54.8/4.18	31.4/1.81-1.88	22.4/1.70-1.75	48.1/3.70		117.2/6.19		39.9/2.41	59.9/3.76	18.5/1.97

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

C/C(=C/C(=O)N(O)CCC[C@@H]1NC(=O)[C@H](CCCN(O)C(=O)/C=C(\C)CCO)NC1=O)CCO[C@@H]1O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]1O

646.691 g/mol (C₂₈H₄₆N₄O₁₃)