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3-Hydroxy-6,7-dimethoxydifuroxanthone - a new metabolite from aspergillus flavus
~~~~~~~~~~
Letters
~0.28,
pp.
3207-3210,
1968.
PergamonPress. Printed in Great Britain.
3-HYDROEy-6,?-DINETNOEYDIFUROEANlNONE - A NEW KETABCLITEFROM ASPERGILLUSFLAWS A. C. Waiss, Jr., M. Wiley, D. R. Black, and R. E. Lundin Western RegionalResearchLaboratory,AgriculturalResearch Service,U.S. Departmentof Agriculture,Albany, California94710
(Receivedin USA 15 Narch 1968; received in UE fc.rpublication15 April 1968) During the isolationof aflatoxinfrom culturesof Aspernillusflavue (1) a
new
metabolite
was isolated. The structureof the compoundwas establishedas 3-hydroxy-6,7-dimethoxydifuroxanthone (Ia) by chemicaland spectroscopicmethods.
Ia
R = CH R' = OH 3'
IIa
R=H
Ib
R = CH R' = H 3'
IIb
R = OH
Ic
R - 8, R' = H
The new metaboliteIa (Rf - 0.65) (2) appears as
a
single blue fluorescentspot on thin-layer
chromatographic plate migratingslightlyahead of aflatoxinMl (IIb,Rf - 0.60). Upon separation and purificationon fine silica Se1 H columns,by gradientelutionwith CHC13 and 5X, MeOH-CHC13 mixture, Ia is obtainedas white needles,m.p. 325-327';[a], 2'-1406 (C = 0.015, DMF) insolublein most organic solvents,however,crystallizablefrom hot d~ethylfor~ide.
The compoundanalyecs
for C19H1407 (Calcd.C, 64.4; H, 3.98. Found: C, 64.1; H, 4.08) and gives a molecularion peak by high resolutionmass spectroscopyof mfe 354.0772,and exhibitshi:: 309 (13,000)and 241 mp (39,000)suggestingthe possibilityof a 6,7-dimethoxydifuroxanthone Q-methylsterigmatocystin), fb nucleus (3). In support of this Ia gives a negativeFeC13 test and its W
spectrumis unaffectedby
the additionof AlCl3, evidencewhich eliminatesthe possibilityof a G-hydroxybenzophenone structure. A negativeGibbs test (5) supportsthe same conclusion. The IR (KBr) spectrumof Ia, absorbing at 1660 (C=O) and 3280 cm-1, (OH) is consistentwith the proposedstructureand furtherreveals
3208
No.28
the prasence of a hydroxy group (4). details (Fig. (I$,
of the proposed structure. Ib)
and the new metabolite
The NWRspectrum of Ia provides A comparison of the NMRspectra
Ia (Fig.
Ia)
clearly
additional
evidence for
of 6,7~~etho~difu~~et~ne
shows the similarity
in the aromatic protons
Hg, W9 and WIO) of the two compounds. With the cumulative diamsgnetic effects
ortho and a para - ethereal
oxygen ataus,
higher
aromatic
field
than
any other
lower field
as a triplet
dashielding
carbonyl functions.
by a six proton singlet
at 2.39 T (J w 8Hx) since it
at 6.07 T.
veraicolor
in 1962 (6),
anthraquinones
is orrho to Hg and 810 and u
Introduction
at
to the
of a hydroxyl group at C3 expectedly
into doublets,
while 114(3.62 T) collapses
of the firet
difuro-mold
numerous other aatural
100 NW_ NM spectra
Bl (IIa)
metabolite,
atigmatocystin,
and synthetic
difuro-containing
(7, 8) and coumarine (9, 10) have been obtained.
FIG. 1.
absorbing
On the other hand, Ii9 appears at
is completely analogous to the one between aflataxin
Since the discovery
from two
The presence of two aromatic methoxyl groups is substantiated
Hl and 82 (3.28 and 4.24 r, respectively) This transformation
83 (3.44 T) is axpected to be a singlet
protons in the molecules.
the
of (a)
Ia and (b)
transforms to a singlet.
and ii1 (IIb).
from Asnerxillw xanthones (3, 6, 7)
With the recent enhanced interest
Ib in gMF-d6 at 90..
No.28
3209
in mold metaboliteait is not unreasonableto expect that many more linear difuro derivativeswill soon be discovered. The nomenclatureof this class of compounds,however,has become increasingly complex (e.g.,aflatoxinB2a and G2a (ll),not to mention the indescribablesyntheticderivatives) so that c-on
names should now be introduced. Since the linear difuro-structure is the only
common feature of these metabolites,any meaningfulsystem of nomenclatureshould be based on this unit. Thus we suggest the name 3-hydroxy-6.8-dimethoxydifuroxanthone for Ia, 6_qethoxydifuro(IIIa)for aflatoxinGl, and 'coumarone(IIa) for aflatoxinBl, 6-methoxydifurocoumarolactone 7,9,10-trihydroxy-difuroanthroquinone for versicolorinA
IIIa
R=H
IIIb
R - OH
(IV)
(8). respectively. i
Iv
The isolationof Ia from Asuernilluaflavus culture is worth noting for at least tvo reasons: Prom a biogeneticpoint of view the co-occurrenceof 6-methoxydifuroxanthone. 6_methoxydifuroco-rone,
6+aethoxycoumarolactone, and some of their 3-hydroxy-and 1,2-dihydro-derivatives
stronglysuggestsa c-on
biosyntheticscheme for these compoundsand that compoundssuch as
IIIb and dihydro-difuroxanthones which are not yet discoveredmight be present also in the culture. Although chemotoxonomyhas been widely applied in higher plants, the occurrenceof difuroxanthonederivativesin both Asnernillusversicolorand flavus indicatesthat chemotoxonomy may be applicablealso for lower organisms. Acknowledgement--The authorswish to acknowledgeseveralhelpful discussionsfrom Drs. R. J. Molyneux and A. C. Keyl. REFERENCES
1. The authorswish to thank Dr. C. W. Resseltineof RURDD, ARS. Peoria, Ill. for the culture used in this work. 2. TLC plates were preparedaccordingto the method describedin M. Wiley, J. Assoc. Offlc. Anal. Chem. 49, 1223 (1966).and were elutedwith 5% MeGIlin CRCl3. --
X0.28
3210 3.
8. .I. Burkhart and J. Forgaca, Tetrahedron ,&
4.
Mass spectroscopic, W, Aauernillus
flaws
717 (1968).
and IR data seem to indicate that Ia and aspertoxin, a metabolite of
of unknown structure [J. V. Rodricks, K. R. Henry-Logan, A. D. Campbell,
L. Stoloff and M. J. Verrett, Nature u,
668 (1968)] are identical.
5.
H. 0. Gibbs, J. Biol. Chem. &,
6.
E. Bullock, J. C. Roberts, and J. G. Underwood, J. Chem. Sot., 4179 (1962).
7.
E. Bullock, D. Kirkaldy, J. C. Roberts, and J. G. Underwood, w.,
8.
T. Ramasaki, Y. Iiatsuda, N. Terashima, and M. Renbutsu, ARr. Biol. Chem. (Japan) a,
9.
T. Asao, G. BUchi, M. M. Abdel Kader, S. B. Chang, E. L. Wick, and G. N. Wogan, J. Amer. Chem. Sot. 4,
649 (1927).
829 (1963). 11 (1967).
1706 (1963).
10.
C. W. Rolzapfel, P. S. Steyn, and I. F. H. Purchase, Tetrahedron Letters, 2799 (1966).
11.
M. F.
Dutton and J. G. Heathcote, Biochem. J. u,
21P (1966).
Letters
~0.28,
pp.
3207-3210,
1968.
PergamonPress. Printed in Great Britain.
3-HYDROEy-6,?-DINETNOEYDIFUROEANlNONE - A NEW KETABCLITEFROM ASPERGILLUSFLAWS A. C. Waiss, Jr., M. Wiley, D. R. Black, and R. E. Lundin Western RegionalResearchLaboratory,AgriculturalResearch Service,U.S. Departmentof Agriculture,Albany, California94710
(Receivedin USA 15 Narch 1968; received in UE fc.rpublication15 April 1968) During the isolationof aflatoxinfrom culturesof Aspernillusflavue (1) a
new
metabolite
was isolated. The structureof the compoundwas establishedas 3-hydroxy-6,7-dimethoxydifuroxanthone (Ia) by chemicaland spectroscopicmethods.
Ia
R = CH R' = OH 3'
IIa
R=H
Ib
R = CH R' = H 3'
IIb
R = OH
Ic
R - 8, R' = H
The new metaboliteIa (Rf - 0.65) (2) appears as
a
single blue fluorescentspot on thin-layer
chromatographic plate migratingslightlyahead of aflatoxinMl (IIb,Rf - 0.60). Upon separation and purificationon fine silica Se1 H columns,by gradientelutionwith CHC13 and 5X, MeOH-CHC13 mixture, Ia is obtainedas white needles,m.p. 325-327';[a], 2'-1406 (C = 0.015, DMF) insolublein most organic solvents,however,crystallizablefrom hot d~ethylfor~ide.
The compoundanalyecs
for C19H1407 (Calcd.C, 64.4; H, 3.98. Found: C, 64.1; H, 4.08) and gives a molecularion peak by high resolutionmass spectroscopyof mfe 354.0772,and exhibitshi:: 309 (13,000)and 241 mp (39,000)suggestingthe possibilityof a 6,7-dimethoxydifuroxanthone Q-methylsterigmatocystin), fb nucleus (3). In support of this Ia gives a negativeFeC13 test and its W
spectrumis unaffectedby
the additionof AlCl3, evidencewhich eliminatesthe possibilityof a G-hydroxybenzophenone structure. A negativeGibbs test (5) supportsthe same conclusion. The IR (KBr) spectrumof Ia, absorbing at 1660 (C=O) and 3280 cm-1, (OH) is consistentwith the proposedstructureand furtherreveals
3208
No.28
the prasence of a hydroxy group (4). details (Fig. (I$,
of the proposed structure. Ib)
and the new metabolite
The NWRspectrum of Ia provides A comparison of the NMRspectra
Ia (Fig.
Ia)
clearly
additional
evidence for
of 6,7~~etho~difu~~et~ne
shows the similarity
in the aromatic protons
Hg, W9 and WIO) of the two compounds. With the cumulative diamsgnetic effects
ortho and a para - ethereal
oxygen ataus,
higher
aromatic
field
than
any other
lower field
as a triplet
dashielding
carbonyl functions.
by a six proton singlet
at 2.39 T (J w 8Hx) since it
at 6.07 T.
veraicolor
in 1962 (6),
anthraquinones
is orrho to Hg and 810 and u
Introduction
at
to the
of a hydroxyl group at C3 expectedly
into doublets,
while 114(3.62 T) collapses
of the firet
difuro-mold
numerous other aatural
100 NW_ NM spectra
Bl (IIa)
metabolite,
atigmatocystin,
and synthetic
difuro-containing
(7, 8) and coumarine (9, 10) have been obtained.
FIG. 1.
absorbing
On the other hand, Ii9 appears at
is completely analogous to the one between aflataxin
Since the discovery
from two
The presence of two aromatic methoxyl groups is substantiated
Hl and 82 (3.28 and 4.24 r, respectively) This transformation
83 (3.44 T) is axpected to be a singlet
protons in the molecules.
the
of (a)
Ia and (b)
transforms to a singlet.
and ii1 (IIb).
from Asnerxillw xanthones (3, 6, 7)
With the recent enhanced interest
Ib in gMF-d6 at 90..
No.28
3209
in mold metaboliteait is not unreasonableto expect that many more linear difuro derivativeswill soon be discovered. The nomenclatureof this class of compounds,however,has become increasingly complex (e.g.,aflatoxinB2a and G2a (ll),not to mention the indescribablesyntheticderivatives) so that c-on
names should now be introduced. Since the linear difuro-structure is the only
common feature of these metabolites,any meaningfulsystem of nomenclatureshould be based on this unit. Thus we suggest the name 3-hydroxy-6.8-dimethoxydifuroxanthone for Ia, 6_qethoxydifuro(IIIa)for aflatoxinGl, and 'coumarone(IIa) for aflatoxinBl, 6-methoxydifurocoumarolactone 7,9,10-trihydroxy-difuroanthroquinone for versicolorinA
IIIa
R=H
IIIb
R - OH
(IV)
(8). respectively. i
Iv
The isolationof Ia from Asuernilluaflavus culture is worth noting for at least tvo reasons: Prom a biogeneticpoint of view the co-occurrenceof 6-methoxydifuroxanthone. 6_methoxydifuroco-rone,
6+aethoxycoumarolactone, and some of their 3-hydroxy-and 1,2-dihydro-derivatives
stronglysuggestsa c-on
biosyntheticscheme for these compoundsand that compoundssuch as
IIIb and dihydro-difuroxanthones which are not yet discoveredmight be present also in the culture. Although chemotoxonomyhas been widely applied in higher plants, the occurrenceof difuroxanthonederivativesin both Asnernillusversicolorand flavus indicatesthat chemotoxonomy may be applicablealso for lower organisms. Acknowledgement--The authorswish to acknowledgeseveralhelpful discussionsfrom Drs. R. J. Molyneux and A. C. Keyl. REFERENCES
1. The authorswish to thank Dr. C. W. Resseltineof RURDD, ARS. Peoria, Ill. for the culture used in this work. 2. TLC plates were preparedaccordingto the method describedin M. Wiley, J. Assoc. Offlc. Anal. Chem. 49, 1223 (1966).and were elutedwith 5% MeGIlin CRCl3. --
X0.28
3210 3.
8. .I. Burkhart and J. Forgaca, Tetrahedron ,&
4.
Mass spectroscopic, W, Aauernillus
flaws
717 (1968).
and IR data seem to indicate that Ia and aspertoxin, a metabolite of
of unknown structure [J. V. Rodricks, K. R. Henry-Logan, A. D. Campbell,
L. Stoloff and M. J. Verrett, Nature u,
668 (1968)] are identical.
5.
H. 0. Gibbs, J. Biol. Chem. &,
6.
E. Bullock, J. C. Roberts, and J. G. Underwood, J. Chem. Sot., 4179 (1962).
7.
E. Bullock, D. Kirkaldy, J. C. Roberts, and J. G. Underwood, w.,
8.
T. Ramasaki, Y. Iiatsuda, N. Terashima, and M. Renbutsu, ARr. Biol. Chem. (Japan) a,
9.
T. Asao, G. BUchi, M. M. Abdel Kader, S. B. Chang, E. L. Wick, and G. N. Wogan, J. Amer. Chem. Sot. 4,
649 (1927).
829 (1963). 11 (1967).
1706 (1963).
10.
C. W. Rolzapfel, P. S. Steyn, and I. F. H. Purchase, Tetrahedron Letters, 2799 (1966).
11.
M. F.
Dutton and J. G. Heathcote, Biochem. J. u,
21P (1966).