General syntheses of 1-alkyltoxoflavin and 8-alkylfervenulin derivatives of biological significance by the regioselective alkylation of reumycin derivatives and the rates of transalkylation from 1-alkyltoxoflavins into nucleophiles

Article abstract of DOI:10.1039/b007302o

Regioselective alkylations of reumycin derivatives under alkaline conditions with a dialkyl sulfate or alkyl halide in 1,4-dioxane or DMF to provide 1-alkyltoxoflavin or 8-alkylfervenulin derivatives of biological significance, are described. Namely, the primary and secondary alkylations of reumycin derivatives with appropriate dialkyl sulfates or alkyl bromides under alkaline conditions in 1,4-dioxane gave predominantly 1-alkyltoxoflavin derivatives, while the same alkylations in DMF instead of 1,4-dioxane gave predominantly 8-alkylfervenulin derivatives. In the case of tertiary alkylation, the reumycin derivative with 2-bromo-2-methylpropane in both solvents under the same conditions yielded only the 1-alkyltoxoflavin derivative. Moreover, the rates of transalkylation from 1-alkyltoxoflavin derivatives into nucleophiles, e.g. DMF and n-butylamine, are also described. That is, the toxoflavin derivatives possessing a primary alkyl group at the 1-position were easily dealkylated from the 1-position by heating with DMF, whereupon reumycin (i.e., 1-dealkyltoxoflavin, 8-dealkylfervenulin) derivatives were formed. In other words, transalkylation from the toxoflavin derivatives into DMF took place, However, the transalkylation of 1-alkyltoxoflavin derivatives possessing a secondary or tertiary alkyl group at the 1-position was not observed under such conditions. On the other hand, when heating 1-alkyltoxoflavin derivatives with n-butylamine in 1,4-dioxane, the transalkylations were more easily observed even in the case of 1-alkyltoxoflavin derivatives substituted by a tertiary alkyl group.

Full text of DOI:10.1039/b007302o

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General syntheses of 1-alkyltoxoflavin and 8-alkylfervenulin
derivatives of biological significance by the regioselective
alkylation of reumycin derivatives and the rates of transalkylation
from 1-alkyltoxoflavins into nucleophiles
1
Tomohisa Nagamatsu* and Hirofumi Yamasaki
Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530,
Japan. E-mail: nagamatsu@pheasant.pharm.okayama-u.ac.jp
Received (in Cambridge, UK) 8th September 2000, Accepted 10th November 2000
First published as an Advance Article on the web 18th December 2000
Regioselective alkylations of reumycin derivatives under alkaline conditions with a dialkyl sulfate or alkyl halide in
1,4-dioxane or DMF to provide 1-alkyltoxoflavin or 8-alkylfervenulin derivatives of biological significance, are
described. Namely, the primary and secondary alkylations of reumycin derivatives with appropriate dialkyl sulfates
or alkyl bromides under alkaline conditions in 1,4-dioxane gave predominantly 1-alkyltoxoflavin derivatives, while
the same alkylations in DMF instead of 1,4-dioxane gave predominantly 8-alkylfervenulin derivatives. In the case
of tertiary alkylation, the reumycin derivative with 2-bromo-2-methylpropane in both solvents under the same
conditions yielded only the 1-alkyltoxoflavin derivative. Moreover, the rates of transalkylation from 1-alkyltoxoflavin
derivatives into nucleophiles, e.g. DMF and n-butylamine, are also described. That is, the toxoflavin derivatives
possessing a primary alkyl group at the 1-position were easily dealkylated from the 1-position by heating with
DMF, whereupon reumycin (i.e., 1-dealkyltoxoflavin, 8-dealkylfervenulin) derivatives were formed. In other
words, transalkylation from the toxoflavin derivatives into DMF took place. However, the transalkylation
of 1-alkyltoxoflavin derivatives possessing a secondary or tertiary alkyl group at the 1-position was not observed
under such conditions. On the other hand, when heating 1-alkyltoxoflavin derivatives with n-butylamine in
1,4-dioxane, the transalkylations were more easily observed even in the case of 1-alkyltoxoflavin derivatives
substituted by a tertiary alkyl group.
Introduction
Since the isolation and characterisation of the naturally
occurring antibiotics of 7-azapteridines (pyrimido[5,4-e][1,2,4]-
triazines), e.g. toxoflavin 1,1 fervenulin 22 and reumycin 33
isolated from Pseudomonas cocovenenans, Streptomyces fervens
n. sp. and Actinomyces, respectively, the 7-azapteridines have
been the subject of a great deal of synthetic study,4 because
of their marked biological activities5,6 (Scheme 1). We have
recently developed several convenient synthetic procedures
for preparation of toxoflavin 1 and its 3- and/or 6-substituted
derivatives,7 and evaluated their potent anti-viral6 and anti-
tumour activities8 and their ability as herbicides.9 These
findings prompted us to explore synthetic methods to prepare
1-substituted toxoflavin type derivatives and the structure–
activity relationships for such activities. However, we
encountered difficulties when attempting to prepare the
derivatives possessing a substituent of some kind at the 1-
position of the toxoflavin skeleton 1 by a method of nitrosative
or nitrative cyclisation of the aldehyde hydrazones of 6-(1-
alkylhydrazino)uracils.6,7 Because it was not easy to get
monosubstituted hydrazines except for methylhydrazine, the
Scheme 1 Reagents and conditions: i, MeI, K2CO3, DMF, reflux;
preparation of several 6-(1-alkylhydrazino)uracils as inter-
mediates of the hydrazones was difficult. Moreover, we have
previously reported that toxoflavin 1 and its 3-substituted
derivatives readily undergo demethylation at the 1-position
upon heating with some nucleophiles, e.g. DMF and dimethyl-
acetamide, to give the corresponding 1-demethyltoxoflavin
(i.e., 8-demethylfervenulin, reumycin) derivatives, while the
nucleophiles themselves were methylated by the methyl group
eliminated, and during the reactions novel radical species were
observed.10 On the other hand, the methylation of reumycin
ii, DMF, reflux.
and its 3-substituted derivatives under alkaline conditions
with dimethyl sulfate or methyl iodide in DMF provided not
toxoflavins but fervenulins.11
We have formerly investigated that the biological activities
of toxoflavins were mostly stronger than those of fervenulins
and reumycins.6,8,9 Despite various biological activities being
expected for the 1-substituted toxoflavin derivatives, no report
130
J. Chem. Soc., Perkin Trans. 1, 2001, 130–137
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b007302o

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on the synthesis except for the methyl derivatives at the
1-position is available so far. In our recent communication12
and a patent,13 we reported a convenient and general method-
ology for the preparation of 1-alkyltoxoflavin derivatives by
the regioselective alkylation of reumycin derivatives under
alkaline conditions with a dialkyl sulfate or alkyl halide in
1,4-dioxane. Herein we report full details of the general syn-
theses of 1-alkyltoxoflavin and 8-alkylfervenulin derivatives
by the regioselective alkylation of reumycin derivatives.
Furthermore, we also report here the rates of transalkylation
from 1-alkyltoxoflavins into nucleophiles, e.g. DMF and
n-butylamine.
Results and discussion
As we reported previously, 3-phenyltoxoflavin 5a was trans-
formed into 3-phenylfervenulin 7a via 3-phenylreumycin 6a
by heating with methyl iodide and potassium carbonate in
DMF in usual alkylating conditions.11 As a consequence of
the demethylation at the 1-position of 3-phenyltoxoflavin
5a due to DMF, the alkylation of the resulting 3-phenyl-
reumycin 6a by methyl iodide proceeded predominantly in
the direction of the 8-position to afford 3-phenylfervenulin
7a. In a similar manner as noted above, we also observed
the transformation of 3,6-diphenyltoxoflavin analogue 5h into
3,6-diphenylfervenulin analogue 7h as described in the Experi-
mental section (Scheme 2).
Fig. 1
Fig. 2
absorption spectra of 3-phenylreumycins 6a,b in different media
as shown in Scheme 1 and the Experimental section. The UV
spectrum of 3-phenyltoxoflavin 5a in 1,4-dioxane showed two
maxima at 293 and 434 nm, while that of 3-phenylfervenulin
7a showed two maxima at 277 and 375 nm (Fig. 1). The
spectra of 3-phenylreumycin 6a in 1,4-dioxane (maxima at 271
and 367 nm) and in acidic medium (pH 1, maxima at 270 and
367 nm) resemble that of 3-phenylfervenulin 7a in 1,4-dioxane
(Fig. 2). On the contrary, the spectrum of 3-phenylreumycin 6a
as the anion in basic medium (pH 10, maxima at 298 and 430
nm) was strikingly similar to that of 3-phenyltoxoflavin 5a in
1,4-dioxane. The UV spectra of 6-phenyl analogue 6b in these
media were also similar to those of 3-phenylreumycin 6a. For
the purpose of the regioselective alkylation at the 1-position of
reumycins 6a,b it is clear that the choice of reaction solvent in the
basic medium was the most important. We found 1,4-dioxane
as the most suitable solvent in the basic medium for the
regioselective alkylation. Indeed, we successfully performed the
alkylation at the 1-position of reumycins 6a,b in basic medium
and 1,4-dioxane, whereupon 1-alkyltoxoflavin derivatives 5a–o
were formed. Incidentally, the same alkylation in DMF instead
of 1,4-dioxane afforded principally fervenulin derivatives 7a–n.
3-Phenyltoxoflavins 5a,h were prepared by nitrosative
cyclisation of the corresponding 6-(2-benzylidene-1-methyl-
hydrazino)-3-methyl (or phenyl)uracils 4b,d according to
our previous methods.6,7 Compounds 5a,h thus obtained were
heated in DMF at 140 ЊC for 5–6 h to afford the desired key
intermediates for the alkylation, i.e., 3-phenylreumycins 6a,b.6,11
Compounds 6a,b were also prepared by nitrosation of 6-benzyl-
idenehydrazino-3-methyl (or phenyl)uracils 4a,c, followed by
refluxing the 5-nitroso intermediates formed in acetic anhydride
for 1 h.15
Scheme 2 Reagents and conditions: i, NaNO2, AcOH, 5–10 ЊC;
ii, Ac2O, reflux; iii, DMF, 140 ЊC or BuNH2, 1,4-dioxane, 100 ЊC;
iv, (R2O)2SO2, R2I or R2Br, K2CO3, DMF, 140 ЊC; v, (R2O)2SO2
or R2Br, K2CO3, 1,4-dioxane, 120 ЊC.
Liao et al.14 suggested that an equilibrium between toxoflavin
type and fervenulin type structures existed under different
environmental conditions with respect to reumycin 3. We also
observed a similar equilibrium in comparison of the ultraviolet
J. Chem. Soc., Perkin Trans. 1, 2001, 130–137
131

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Table 1 Preparative conditions and yields for toxoflavin 5a–o and fervenulin derivatives 7a–n by alkylation of reumycin derivatives 6a,b
Substituents
Reaction conditionsa Isolated product and yield (%)b
Toxoflavin-type Fervenulin-type
Alkylating
agent
Run
Substrate
R1
R2
Solvent
Temp/ЊC
Time/h
1
2
3
4
5
6
7
8
9
6a
6a
6a
6a
6a
6a
6a
6a
6a
6a
6a
6a
6a
6a
6a
6a
6b
6b
6b
6b
6b
6b
6b
6b
6b
6b
6b
6b
6b
6b
6b
6b
6b
6b
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Me
Me
Me
Et
Et
Et
Pr
Pr
(R2O)2SO2
(R2O)2SO2
R2I
1,4-Dioxane
DMF
1,4-Dioxane
1,4-Dioxane
DMF
1,4-Dioxane
1,4-Dioxane
DMF
1,4-Dioxane
DMF
1,4-Dioxane
DMF
1,4-Dioxane
DMF
1,4-Dioxane
DMF
1,4-Dioxane
DMF
1,4-Dioxane
1,4-Dioxane
DMF
1,4-Dioxane
1,4-Dioxane
DMF
1,4-Dioxane
DMF
1,4-Dioxane
DMF
1,4-Dioxane
DMF
1,4-Dioxane
DMF
1,4-Dioxane
DMF
120
140
120
120
140
120
120
140
120
140
120
140
120
140
120
140
120
140
120
120
140
120
120
140
120
140
120
140
120
140
120
140
120
140
2
2
2
2
2
2
2
2
2
2
5
5
5
5
3
3
2
2
2
2
2
2
2
2
2
2
5
5
5
5
3
3
7
9
5a (91)
N.I.
N.I.
5b (79)
N.I.
N.I.
5c (80)
N.I.
5d (82)
N.I.
5e (81)
N.I.
5f (79)
5f (33)
5g (85)
N.I.
5h (86)
N.I.
N.I.
5i (76)
N.I.
N.I.
5j (88)
N.I.
5k (82)
N.I.
5l (85)
N.I.
5m (81)
5m (40)
5n (78)
N.I.
5o (85)
N.I.
N.I.
7a (89)
7a (80)
N.I.
7b (86)
7b (85)
N.I.
7c (78)
N.I.
7d (81)
N.I.
7e (65)
N.I.
7f (42)
N.I.
7g (67)
N.I.
7h (85)
7h (78)
N.I.
7i (75)
7i (81)
N.I.
7j (84)
N.I.
7k (80)
N.I.
7l (72)
N.I.
7m (49)
N.I.
7n (82)
N.I.
N.I.
(R2O)2SO2
(R2O)2SO2
R2I
(R2O)2SO2
(R2O)2SO2
(R2O)2SO2
(R2O)2SO2
R2Br
Bu
Bu
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
Cyclopentyl
Cyclopentyl
Cyclohexyl
R2Br
R2Br
Cyclohexyl
R2Br
Pri
R2Br
Pri
R2Br
Me
Me
Me
Et
Et
Et
Pr
Pr
(R2O)2SO2
(R2O)2SO2
R2I
(R2O)2SO2
(R2O)2SO2
R2I
(R2O)2SO2
(R2O)2SO2
(R2O)2SO2
(R2O)2SO2
R2Br
Bu
Bu
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Cyclopentyl
Cyclopentyl
Cyclohexyl
Cyclohexyl
Pri
R2Br
R2Br
R2Br
R2Br
Pri
R2Br
But
R2Br
Ph
But
R2Br
a All reactions were heated in the presence of anhydrous potassium carbonate as a base (method A). b N.I. means not isolated.
The primary alkylation of reumycin derivatives 6a,b is
described below. As can be seen from runs 1, 4, 7, 9, 17, 20, 23
and 25 in Table 1, a mixture of compound 6a or 6b, dialkyl
sulfate (3 equiv.) and anhydrous potassium carbonate (2 equiv.)
in 1,4-dioxane was heated in a sealed vessel under an atmos-
phere of argon at 120 ЊC for 2 h to afford the corresponding
1-alkyltoxoflavin type compounds 5a–d,h–k in 76–91% yields
(method A). The above alkylations of reumycins 6a,b with other
bases, e.g. sodium hydride and sodium hydrogen carbonate, were
also accomplished in the same direction to get the toxoflavin
derivatives 5a–d,h–k in 65–88% yields as shown in the Experi-
mental section (methods B and C). However, the use of alkyl
iodides as the alkylating agent in the above reaction gave not
the corresponding 1-alkyltoxoflavin type compounds 5a,b,h,i
but 8-alkylfervenulin type compounds 7a,b,h,i in 78–85% yields
(method D, runs 3, 6, 19 and 22). When the same reactions were
carried out in DMF instead of 1,4-dioxane at 140 ЊC for 2 h, the
corresponding 8-alkylfervenulin type compounds 7a–d,h–k
formed in 75–89% yields (method E, runs 2, 5, 8, 10, 18, 21,
24 and 26). The secondary alkylation is as follows: the similar
reaction of reumycins 6a,b with an appropriate alkyl bromide
(3 equiv.), e.g. cyclopentyl bromide, cyclohexyl bromide and 2-
bromopropane, and anhydrous potassium carbonate (2 equiv.)
in 1,4-dioxane afforded the corresponding 1-alkyltoxoflavin
type compounds 5e–g,l–n in 78–85% yields (method F, runs 11,
13, 15, 27, 29 and 31). In the same manner, the secondary
alkylation with sodium hydride or sodium hydrogen carbonate
instead of potassium carbonate also yielded the corresponding
1-alkyltoxoflavin type compounds 5e–g,l–n in 73–87% yields
(methods G and H). On the other hand, the alkylation of
reumycins 6a,b with an appropriate cyclopentyl bromide or 2-
bromopropane (3 equiv.) and anhydrous potassium carbonate
(2 equiv.) in DMF gave the corresponding 8-alkylfervenulin
derivatives 7e,g,l,n in 65–82% yields (method I, runs 12, 16,
28 and 32). In the case of the above reaction with cyclohexyl
bromide (3 equiv.) as an alkylating agent, the alkylated product
was a mixture of 1-alkyltoxoflavin 5f (33%), 5m (40%) and
8-alkylfervenulin derivative 7f (42%), 7m (49%), respectively
(runs 14 and 30). Finally, the tertiary alkylation is as follows.
The reaction of reumycin derivative 6b with 2-bromo-2-
methylpropane (3 equiv.) and anhydrous potassium carbonate
(2 equiv.) in 1,4-dioxane at 120 ЊC for 7 h afforded 1-tert-
butyltoxoflavin derivative 5o in 85% yield (method J, run 33).
When the same reaction was carried out in DMF, no alkylated
product was obtained owing to steric hindrance between the
carbonyl at the 7-position and the tert-butyl group at the
8-position to produce the expected 8-tert-butylfervenulin 7o
(run 34). The structures of the products 5a,h and 7a–c,g were
1
determined by comparison of IR and H NMR spectral data
of the authentic samples, respectively, and other new com-
pounds 5 and 7 were assigned on the basis of elemental
analyses and satisfactory spectral data as shown in Tables 2
and 3. As a general rule, the ultraviolet spectra of toxoflavin
type compounds 5a–o in 1,4-dioxane showed two maximum
absorption bands at ca. 295 and 435 nm, while those of
fervenulin type compounds 7a–n did at ca. 280 and 375 nm.
That is, bathochromic shifts of about 60 nm at the longer
wavelength band for toxoflavins 5a–o were observed in com-
parison with those for fervenulins 7a–n. The mechanism of the
above regioselective alkylations is as follows. The real structure
of reumycins 3 and 6 in basic solution may be of toxoflavin type
structure rather than the fervenulin type structure as noted in
132
J. Chem. Soc., Perkin Trans. 1, 2001, 130–137

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Table 2 Physical and analytical data for the compounds 5a–o and 7a–n
Found (%) (Required)
Compound
(Formula)
λmax/nm
f
Mp/ЊCa
TLC (Rf)e
νmax(KBr)/cmϪ1
(log ε/dm3 molϪ1 cmϪ1
)
C
H
N
b
5a
228 (Decomp.)b
163 (Decomp.)
169 (Decomp.)
172 (Decomp.)
228–230
0.48
0.51
0.53
0.57
0.58
0.58
0.50
0.42
0.50
0.55
0.57
0.58
0.59
0.55
0.55
0.73
0.72
0.73
0.72
0.76
0.76
0.74
0.65
0.65
0.65
0.66
0.76
0.76
0.66
1660, 1700 (C᎐O)
293 (4.29), 434 (3.30)
291 (4.35), 436 (3.36)
294 (4.33), 436 (3.35)
294 (4.41), 435 (3.47)
295 (4.38), 436 (3.45)
294 (4.41), 434 (3.51)
294 (4.30), 436 (3.33)
296 (4.37), 434 (3.38)
298 (4.41), 436 (3.42)
295 (4.41), 436 (3.36)
294 (4.48), 436 (3.47)
299 (4.48), 436 (3.53)
296 (4.50), 434 (3.60)
297 (4.41), 435 (3.41)
296 (4.43), 436 (3.46)
277 (4.30), 375 (3.41)
279 (4.30), 372 (3.48)
276 (4.34), 375 (3.33)
281 (4.36), 377 (3.46)
280 (4.33), 376 (3.43)
280 (4.38), 374 (3.47)
276 (4.31), 375 (3.32)
280 (4.38), 377 (3.44)
281 (4.36), 377 (3.40)
281 (4.29), 376 (3.55)
280 (4.41), 376 (3.49)
282 (4.47), 374 (3.53)
281 (4.49), 374 (3.55)
281 (4.41), 374 (3.44)
᎐
C13H11N5O2
5b
1660, 1715 (C᎐O)
59.5
(59.4)
60.5
(60.6)
61.85
(61.7)
63.0
(63.15)
63.9
(64.1)
60.9
4.8
(4.6)
5.2
(5.1)
5.6
(5.5)
5.4
(5.3)
5.6
24.8
(24.7)
23.7
(23.6)
22.55
(22.5)
21.6
(21.7)
20.65
(20.8)
23.5
᎐
C14H13N5O2
5c
1670, 1715 (C᎐O)
᎐
C15H15N5O2
5d
1665, 1710 (C᎐O)
᎐
C16H17N5O2
5e
1660, 1710 (C᎐O)
᎐
C17H17N5O2
5f
273–275
1660, 1715 (C᎐O)
᎐
C18H19N5O2
(5.7)
5.2
5g
252–254
1665, 1715 (C᎐O)
᎐
C15H15N5O2
(60.6)
(5.1)
(23.6)
c
5h
245 (Decomp.)c
192 (Decomp.)
135 (Decomp.)
178 (Decomp.)
224–226
1660, 1720 (C᎐O)
᎐
C18H13N5O2
5i
1675, 1720 (C᎐O)
66.0
(66.1)
66.6
(66.8)
66.8
(66.7)
68.7
(68.6)
68.9
(69.2)
66.7
(66.8)
67.6
4.3
(4.4)
5.0
(4.8)
5.1
(5.2)
5.1
(5.0)
5.1
(5.3)
4.7
(4.8)
5.15
20.2
(20.3)
19.4
(19.5)
18.7
(18.5)
18.35
(18.2)
17.6
(17.5)
19.4
᎐
C19H15N5O2
5j
1680, 1720 (C᎐O)
᎐
C20H17N5O2
5k
1670, 1720 (C᎐O)
᎐
C21H19N5O2ؒ1/4 H2O
5l
1675, 1720 (C᎐O)
᎐
C22H19N5O2
5m
C23H21N5O2
286–288
1680, 1720 (C᎐O)
᎐
5n
237–239
1675, 1720 (C᎐O)
᎐
C20H17N5O2
(19.5)
18.9
(18.75)
5o
275–277
1670, 1715 (C᎐O)
᎐
C21H19N5O2
(67.55)
(5.1)
d
7a
277–279d
1680, 1730 (C᎐O)
᎐
C13H11N5O2
d
d
7b
226–228d
1675, 1725 (C᎐O)
᎐
C14H13N5O2
7c
212–214d
1680, 1730 (C᎐O)
᎐
C15H15N5O2
7d
179–181
1680, 1730 (C᎐O)
61.55
(61.7)
63.0
(63.15)
63.95
(64.1)
5.5
(5.5)
5.1
(5.3)
5.8
22.7
(22.5)
21.8
(21.7)
20.7
᎐
C16H17N5O2
7e
211–213
1685, 1730 (C᎐O)
᎐
C17H17N5O2
7f
207–209
1680, 1730 (C᎐O)
᎐
C18H19N5O2
(5.7)
(20.8)
d
7g
224–226d
1680, 1730 (C᎐O)
᎐
C15H15N5O2
7h
269–271
1690, 1735 (C᎐O)
65.4
(65.25)
64.45
(64.4)
66.7
(66.8)
67.3
(67.55)
68.3
(68.6)
69.35
(69.2)
66.7
4.2
(3.95)
4.45
(4.55)
4.8
(4.8)
4.9
(5.1)
4.8
(5.0)
5.1
21.3
(21.1)
19.8
(19.8)
19.35
(19.5)
18.8
(18.8)
18.3
(18.2)
17.6
᎐
C18H13N5O2
7i
242–244
1690, 1730 (C᎐O)
᎐
C19H15N5O2ؒ1/2 H2O
7j
237–239
1690, 1735 (C᎐O)
᎐
C20H17N5O2
7k
220–222
1690, 1735 (C᎐O)
᎐
C21H19N5O2
7l
C22H19N5O2
7m
C23H21N5O2
7n
C20H17N5O2
247–249
1690, 1730 (C᎐O)
᎐
282–284
1690, 1735 (C᎐O)
᎐
(5.3)
4.7
(4.8)
(17.5)
19.4
(19.5)
244–246
1685, 1730 (C᎐O)
᎐
(66.8)
a All products were recrystallised from 40% aqueous 1,4-dioxane and were obtained as yellow or orange needles. b Ref. 7. c Ref. 6. d Ref. 11. e All
thin-layer chromatograms (TLC) were obtained by developing in ethyl acetate. f All UV spectra were measured in 1,4-dioxane.
the UV spectra. Therefore, the alkylation of reumycins 6 under
basic conditions in 1,4-dioxane gave predominantly 1-alkyl-
toxoflavins 5. However, the same alkylation in DMF instead
of 1,4-dioxane afforded predominantly 8-alkylfervenulins 7
because of the character of facile dealkylation of 1-alkyl-
toxoflavins 5 produced by the alkylation in heating DMF.
By the way, the 1-alkyltoxoflavins 5 were stable for more than
12 hours on heating in 1,4-dioxane, water and ethanol.
5a–o into nucleophiles such as DMF and n-butylamine. Thus
the reactions were carried out by heating compounds 5a–o
(3 mmol) with DMF (10 cm3) at 140 ЊC for 3 h and by heating
compounds 5d–g,k–o (3 mmol) with a mixture of n-butyl-
amine (1 cm3) and 1,4-dioxane (10 cm3) at 100 ЊC for 1 h.
The dealkylation of 3-phenyltoxoflavins 5a–d in DMF was
readily observed (runs 1–4), while the rate of dealkylation of
3,6-diphenyltoxoflavins 5h–k was apparently retarded with
increasing the alkyl chain length at the 1-position (runs 5–8).
On the other hand, the dealkylation of compounds 5e–g,l–o
possessing a secondary or tertiary alkyl group was not observed
It is necessary to evaluate the extent of dealkylation of 1-
alkyltoxoflavin type derivatives 5 for their chemical stabilities.
Table 4 shows the transalkylation from toxoflavin derivatives
J. Chem. Soc., Perkin Trans. 1, 2001, 130–137
133

View Article Online
Table 3 1H NMR spectroscopic data for the compounds 5a–o and 7a–n
Compound
δH [200 MHz; (CD3)2SO; Me4Si]
5aa
5ba
3.29 (3 H, s, 6-Me), 4.06 (3 H, s, 1-Me), 7.53–7.65 (3 H, m, Ph-m,pH), 8.08–8.28 (2 H, m, Ph-oH)
1.48 (3 H, t, J 7.0, CH2CH3), 3.29 (3 H, s, 6-Me), 4.50 (2 H, q, J 7.0, CH2CH3), 7.50–7.72 (3 H, m, Ph-m,pH), 8.15–8.30 (2 H, m,
Ph-oH)
1.00 (3 H, t, J 7.0, [CH2]2CH3), 1.97 (2 H, pseudosextet, CH2CH2CH3), 3.29 (3 H, s, 6-Me), 4.42 (2 H, t, J 7.0, CH2CH2CH3), 7.50–7.70
(3 H, m, Ph-m,pH), 8.12–8.31 (2 H, m, Ph-oH)
0.95 (3 H, t, J 7.3, [CH2]3CH3), 1.41 (2 H, sex, J 7.3, [CH2]2CH2CH3), 1.90 (2 H, quin, J 7.4, CH2CH2CH2CH3), 3.27 (3 H, s, 6-Me),
4.45 (2 H, t, J 7.2, CH2[CH2]2CH3), 7.58–7.62 (3 H, m, Ph-m,pH), 8.18–8.21 (2 H, m, Ph-oH)
1.70–2.26 (8 H, m, cyclopentyl-H), 3.27 (3 H, s, 6-Me), 5.67 (1 H, pseudoquintet, cyclopentyl-H), 7.55–7.64 (3 H, m, Ph-m,pH),
8.14–8.23 (2 H, m, Ph-oH)
5ca
5d
5e
5f
1.13–2.06 (10 H, m, cyclohexyl-H), 3.27 (3 H, s, 6-Me), 5.10–5.28 (1 H, m, cyclohexyl-H), 7.56–7.66 (3 H, m, Ph-m,pH), 8.18–8.27
(2 H, m, Ph-oH)
1.50 (6 H, d, J 6.5, CH[CH3]2), 3.29 (3 H, s, 6-Me), 5.55 (1 H, quin, J 6.5, CH[CH3]2), 7.50–7.70 (3 H, m, Ph-m,pH), 8.15–8.37 (2 H,
m, Ph-oH)
5ga
5h
4.11 (3 H, s, 1-Me), 7.19–7.29 (2 H, m, 6-Ph-mH), 7.41–7.66 (6 H, 3-Ph-m,pH and 6-Ph-o,pH), 8.17–8.27 (2 H, m, 3-Ph-oH)
1.52 (3 H, t, J 7.1, CH2CH3), 4.55 (2 H, q, J 7.1, CH2CH3), 7.16–7.34 (2 H, m, 6-Ph-mH), 7.42–7.65 (6 H, m, 3-Ph-m,pH and 6-Ph-
o,pH), 8.12–8.34 (2 H, m, 3-Ph-oH)
5ia
5j
0.98 (3 H, t, J 7.3, [CH2]2CH3), 1.86 (2 H, sex, J 7.3, CH2CH2CH3), 3.96 (2 H, t, J 7.1, CH2CH2CH3), 7.46–7.55 (4 H, m, 3-Ph-pH
and 6-Ph-m,pH), 7.57–7.67 (2 H, m, 3-Ph-mH), 7.69–7.76 (2 H, m, 6-Ph-oH), 8.21–8.29 (2 H, m, 3-Ph-oH)
0.95 (3 H, t, J 7.3, [CH2]3CH3), 1.42 (2 H, sex, J 7.3, [CH2]2CH2CH3), 1.83 (2 H, quin, J 7.4, CH2CH2CH2CH3), 4.01 (2 H, t, J 7.1,
CH2[CH2]2CH3), 7.48–7.55 (4 H, m, 3-Ph-pH and 6-Ph-m,pH), 7.58–7.67 (2 H, m, 3-Ph-mH), 7.70–7.76 (2 H, m, 6-Ph-oH), 8.21–8.29
(2 H, m, 3-Ph-oH)
5k
5l
1.70–2.30 (8 H, m, cyclopentyl-H), 5.74 (1 H, pseudoquintet, cyclopentyl-H), 7.20–7.27 (2 H, m, 6-Ph-mH), 7.38–7.66 (6 H, m, 3-Ph-
m,pH and 6-Ph-o,p-H), 8.14–8.26 (2 H, m, 3-Ph-oH)
5m
5na
1.20–2.15 (10 H, m, cyclohexyl-H), 5.10–5.30 (1 H, m, cyclohexyl-H), 7.17–7.27 (2 H, m, 6-Ph-mH), 7.42–7.57 (6 H, m, 3-Ph-m,pH
and 6-Ph-o,pH), 8.15–8.29 (2 H, m, 3-Ph-oH)
1.54 (6 H, d, J 6.5, CH[CH3]2), 5.62 (1 H, quin, J 6.5, CH[CH3]2), 7.15–7.34 (2 H, m, 6-Ph-mH), 7.42–7.66 (6 H, m, 3-Ph-m,pH and
6-Ph-o,p-H), 8.14–8.38 (2 H, m, 3-Ph-oH)
1.89 (9 H, s, 3 × Me), 7.23–7.70 (8 H, m, 3-Ph-m,pH and 6-Ph-o,m,pH), 8.14–8.36 (2 H, m, 3-Ph-oH)
3.37 (3 H, s, 6-Me), 3.73 (3 H, s, 8-Me), 7.54–7.80 (3 H, m, Ph-m,pH), 8.34–8.56 (2 H, m, Ph-oH)
1.32 (3 H, t, J 7.0, CH2CH3), 3.37 (3 H, s, 6-Me), 4.42 (2 H, q, J 7.0, CH2CH3), 7.57–7.76 (3 H, m, Ph-m,pH), 8.35–8.57 (2 H, m,
Ph-oH)
5oa
7a
7ba
7c
7d
7e
7f
0.97 (3 H, t, J 7.4, [CH2]2CH3), 1.94 (2 H, sex, J 7.3, CH2CH2CH3), 3.35 (3 H, s, 6-Me), 4.31 (2 H, t, J 7.2, CH2CH2CH3), 7.58–7.64
(3 H, m, Ph-m,pH), 8.39–8.46 (2 H, m, Ph-oH)
0.94 (3 H, t, J 7.3, [CH2]3CH3), 1.41 (2 H, sex, J 7.3, [CH2]2CH2CH3), 1.71 (2 H, pseudoquintet, CH2CH2CH2CH3), 3.35 (3 H, s, 6-Me),
4.35 (2 H, t, J 7.3, CH2[CH2]2CH3), 7.58–7.64 (3 H, m, Ph-m,pH), 8.38–8.46 (2 H, m, Ph-oH)
1.60–1.75 (2 H, m, cyclopentyl-H), 1.88–2.10 (4 H, m, cyclopentyl-H), 2.14–2.30 (2 H, m, cyclopentyl-H), 3.34 (3 H, s, 6-Me), 5.86
(1 H, pseudoquintet, cyclopentyl-H), 7.59–7.64 (3 H, m, Ph-m,pH), 8.38–8.45 (2 H, m, Ph-oH)
1.18–1.56 (3 H, m, cyclohexyl-H), 1.65–1.96 (5 H, m, cyclohexyl-H), 2.40–2.63 (2 H, m, cyclohexyl-H), 3.33 (3 H, s, 6-Me), 5.31
(1 H, br pseudotriplet, cyclohexyl-H), 7.58–7.67 (3 H, m, Ph-m,pH), 8.38–8.47 (2 H, m, Ph-oH)
1.61 (6 H, d, J 7.0, CH[CH3]2), 3.35 (3 H, s, 6-Me), 5.65 (1 H, quin, J 7.0, CH[CH3]2), 7.55–7.70 (3 H, m, Ph-m,pH), 8.34–8.50
(2 H, m, Ph-oH)
7ga
7ha
7ia
3.75 (3 H, s, 8-Me), 7.23–7.74 (8 H, m, 3-Ph-m,pH and 6-Ph-o,m,pH), 8.36–8.57 (2 H, m, 3-Ph-oH)
1.36 (3 H, t, J 7.0, CH2CH3), 4.44 (2 H, q, J 7.0, CH2CH3), 7.23–7.76 (8 H, m, 3-Ph-m,pH and 6-Ph-o,m,pH), 8.34–8.60 (2 H, m,
3-Ph-oH)
7j
0.99 (3 H, t, J 7.4 [CH2]2CH3), 1.79 (2 H, sex, J 7.3, CH2CH2CH3), 4.34 (2 H, t, J 7.3, CH2CH2CH3), 7.30–7.36 (2 H, m, 6-Ph-mH),
7.46–7.56 (3 H, m, 6-Ph-o,pH), 7.60–7.66 (3 H, m, 3-Ph-m,pH), 8.41–8.48 (2 H, m, 3-Ph-oH)
0.94 (3 H, t, J 7.3, [CH2]3CH3), 1.43 (2 H, sex, J 7.3, [CH2]2CH2CH3), 1.75 (2 H, pseudoquintet, CH2CH2CH2CH3), 4.37 (2 H, t, J 7.3,
CH2[CH2]2CH3), 7.30–7.37 (2 H, m, 6-Ph-mH), 7.47–7.56 (3 H, m, 6-Ph-o,pH), 7.60–7.68 (3 H, m, 3-Ph-m,pH), 8.41–8.49 (2 H, m,
3-Ph-oH)
7k
7l
1.55–1.74 (2 H, m, cyclopentyl-H), 1.87–2.07 (4 H, m, cyclopentyl-H), 2.14–2.35 (2 H, m, cyclopentyl-H), 5.88 (1 H, br pseudotriplet,
cyclopentyl-H), 7.30–7.39 (2 H, m, 6-Ph-mH), 7.47–7.70 (6 H, m, 3-Ph-m,pH and 6-Ph-o,pH), 8.40–8.52 (2 H, m, 3-Ph-oH)
1.15–1.55 (3 H, m, cyclohexyl-H), 1.62–1.95 (5 H, m, cyclohexyl-H), 2.40–2.60 (2 H, m cyclohexyl-H), 5.31 (1 H, br pseudotriplet),
7.29–7.37 (2 H, m, 3-Ph-mH), 7.46–7.56 (3 H, m, 6-Ph-o,pH), 7.60–7.66 (3 H, m, 3-Ph-m,pH), 8.41–8.48 (2 H, m, 3-Ph-oH)
1.61 (6 H, d, J 7.0, CH[CH3]2), 5.65 (1 H, quin, J 7.0, CH[CH3]2), 7.22–7.80 (8 H, m, 3-Ph-m,pH and 6-Ph-o,m,pH), 8.34–8.60
(2 H, m, 3-Ph-oH)
7m
7na
a This compound was measured at 60 MHz.
under these conditions (runs 9–15). However, the dealkylation
of compounds 5d–g,k–o, even compound 5o possessing a
tert-alkyl group, by n-butylamine as a stronger nucleophile
took place easily, and the nucleophile itself is presumably
alkylated by the alkyl groups eliminated (runs 16–24). Previ-
ously, we have reported a possible reaction mechanism as
follows. That was, toxoflavin 1 and its 3-substituted derivatives
readily underwent demethylation with several nucleophiles
e.g. DMF and dimethylacetamide, to give the corresponding
Conclusion
Thus, we reported the first successful synthesis of 1-substituted
toxoflavin derivatives 5 by the regioselective alkylation of
reumycins 6, and this simple methodology provided a facile and
convenient route to the preparation of 1-alkyltoxoflavins 5
which are biologically more active than 8-alkylfervenulins 7.
Moreover, the rates of transalkylation from 1-alkyltoxoflavin
derivatives 5 into nucleophiles such as DMF and n-butylamine
to produce reumycins 6 were also determined.
1-demethyltoxoflavin (reumycin)
3 and its 3-substituted
derivatives and during the reactions novel radical species,
i.e. toxoflavin radical anions, were observed.10 On the other
hand, DMF or dimethylacetamide could be methylated into
reactive dimethylformamide ether or dimethylacetamide ether,
which is readily hydrolysed into methanol and the original
solvents.
Experimental
General
Mps were obtained on a Yanagimoto micro melting point
apparatus and were uncorrected. Microanalyses were measured
134
J. Chem. Soc., Perkin Trans. 1, 2001, 130–137

View Article Online
Table 4 Transalkylation from toxoflavins 5a–o into nucleophiles such
as DMF and n-butylamine to produce reumycins 6a,b
was evaporated in vacuo to leave a solid, which was recrystal-
lised to afford the pure fervenulin derivative 7h (0.43 g, 65%) as
yellow needles and shown in Tables 2 and 3.
Proportion
Starting material
of analysed
materials
6-Methyl-3-phenylpyrimido[5,4-e][1,2,4]triazine-5,7(6H,8H)-
dione (3-phenylreumycin) 6a
Run
R1
R2
Nucleophilea
5:6 (%)b
A solution of 3-phenyltoxoflavin 5a7 (5.0 g, 18.6 mmol) in
DMF (70 cm3) was heated at 140 ЊC for 5 hours. Concentration
of the solution in vacuo and recrystallisation of the residue
from EtOH gave 3-phenylreumycin 6a (4.1 g, 86%), which was
identical with an authentic sample,11 as pale green crystals,
mp > 320 ЊC; Rf (EtOAc) 0.59; νmax/cmϪ1 3170 (NH), 1735
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
5a
5b
5c
5d
5h
5i
Me
Me
Me
Me
Ph
Ph
Ph
Me
Et
Pr
Bu
Me
Et
Pr
Bu
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
BuNH2
BuNH2
BuNH2
BuNH2
BuNH2
BuNH2
BuNH2
BuNH2
BuNH2
0:100 (91)
0:100 (93)
0:100 (89)
0:100 (86)
0:100 (90)
10: 90 (95)
10: 90 (91)
50: 50 (88)
5j
and 1670 (C᎐O); δH [200 MHz; (CD3)2SO] 3.30 (3 H, s, 6-Me),
᎐
5k
5e
5f
5g
5l
5m
5n
5o
5d
5e
5f
5g
5k
5l
Ph
7.58–7.66 (3 H, m, Ph-m,pH), 8.37–8.45 (2 H, m, Ph-oH)
and 12.48 (1 H, s, 8-H); λmax (1,4-dioxane)/nm 271 (log ε
4.26) and 367 (3.42); λmax (pH 1 buffer)/nm 270 (log ε 4.21)
and 367 (3.11); λmax (pH 10 buffer)/nm 298 (log ε 4.19) and
430 (3.39).
Me
Me
Me
Ph
Ph
Ph
Cyclopentyl
Cyclohexyl
Pri
100:
100:
100:
100:
100:
100:
100:
0
0
0
0
0
0
0
Cyclopentyl
Cyclohexyl
Pri
Ph
But
Bu
3,6-Diphenylpyrimido[5,4-e][1,2,4]triazine-5,7(6H,8H)-dione
(3,6-diphenylreumycin) 6b
Me
Me
Me
Me
Ph
Ph
Ph
0:100 (86)
0:100 (88)
0:100 (84)
0:100 (87)
0:100 (83)
0:100 (85)
0:100 (82)
0:100 (80)
50: 50 (78)
Cyclopentyl
Cyclohexyl
Pri
A solution of 3,6-diphenyltoxoflavin 5h6 (10.0 g, 30.2 mmol)
in DMF (120 cm3) was heated at 140 ЊC for 6 hours. Concen-
tration of the solution in vacuo and recrystallisation of the
residue gave 3,6-diphenylreumycin 6b (7.9 g, 82%), which was
identical with an authentic sample,6 as yellow crystals, mp
328–330 ЊC; Rf (EtOAc) 0.64; νmax/cmϪ1 3420 (NH), 1735 and
1690 (C᎐O); δ [60 MHz; (CD3)2SO] 7.21–7.78 (8 H, m, 3-Ph-
Bu
Cyclopentyl
Cyclohexyl
Pri
5m
5n
5o
Ph
Ph
But
a The dealkylation in DMF was carried out at 140 ЊC for 3 h, while
in n-butylamine–1,4-dioxane (1:10) it was carried out at 100 ЊC for
1 h. b The yields given in parentheses represent isolated total yields.
᎐
H
m,pH and 6-Ph-o,m,pH), 8.36–8.52 (2 H, m, 3-Ph-oH) and
12.96 (1 H, s, 8-NH); λmax (1,4-dioxane)/nm 276 (log ε 4.40)
and 373 (3.52); λmax (pH 1 buffer)/nm 277 (log ε 4.39) and
372 (3.22); λmax (pH 10 buffer)/nm 294 (log ε 4.40) and 413
(3.54).
on a Yanaco CHN Corder MT-5 apparatus. IR spectra were
recorded on a JASCO IRA-102 spectrometer. Ultraviolet (UV)
spectra were recorded with a Beckman DU-68 spectrophoto-
meter. 1H NMR spectra were obtained using Hitachi FT-NMR
R-1500 (60 MHz) and Varian VXR 200 MHz spectrometers.
In all cases, chemical shifts are in δ (ppm) relative to TMS
as internal standards, J-values are given in Hz, and signals are
quoted as follows: s, singlet, d, doublet; t, triplet; q, quartet;
quin, quintet; sex, sextet; br, broad; m, multiplet. All reagents
were of commercial quality from freshly opened containers
and were used without further purification. Organic solvents
were dried by standard methods and distilled before use.
Reaction progress was monitored by analytical thin layer
chromatography (TLC) on pre-coated aluminium-backed
plates (Merck Kieselgel 60 F254) using ethyl acetate as the
developing solvent and products were visualised by UV light.
Column chromatography was run on Kiesel gel 60 (70–230
mesh ASTM, Merck) and eluted with benzene–EtOAc (9:1).
All reactions in a sealed vessel were carried out under an
atmosphere of argon and all products were recrystallised from
1,4-dioxane, unless otherwise noted. The reaction temperatures
are indicated as the temperature of the oil bath.
Regioselective alkylation of reumycin derivatives 6a,b by primary
alkylating agents
Toxoflavin derivatives 5a–d,h–k; general procedure. Method A.
To reumycin 6a or 6b (2.0 mmol) and anhydrous potassium
carbonate (0.55 g, 4.0 mmol) in 1,4-dioxane (50 cm3) was added
an appropriate dialkyl sulfate (6.0 mmol) and the stirring
mixture was heated under reflux at 120 ЊC for 2 hours. After
cooling, the precipitated potassium carbonate was filtered off
and the filtrate was concentrated in vacuo. A solution of the
residue in water (100 cm3) was extracted with ethyl acetate
(3 × 30 cm3) and the combined extracts were dried over
anhydrous MgSO4. Then the extract was evaporated in vacuo
to leave a solid, which was recrystallised to afford the corre-
sponding pure toxoflavin derivatives 5a–d,h–k as shown in
Tables 1 (runs 1, 4, 7, 9, 17, 20, 23 and 25), 2 and 3.
Method B. To reumycin 6a or 6b (2.0 mmol) and 60% sodium
hydride (oil dispersion, 0.16 g, 4.0 mmol) in 1,4-dioxane
(50 cm3) was added an appropriate dialkyl sulfate (6.0 mmol)
and the mixture was stirred at room temperature for 10–20
hours. After the reaction monitored by TLC was complete,
the precipitated sodium hydride was filtered off and the fil-
trate was concentrated in vacuo. A solution of the residue
in water (100 cm3) was extracted with ethyl acetate (3 × 30
cm3) and the combined extracts were dried over anhydrous
MgSO4. Then the extract was evaporated in vacuo to leave
a solid, which was washed with diethyl ether and recrystallised
to afford the corresponding pure toxoflavin derivatives 5a
(81), 5b (85), 5c (79), 5d (76), 5h (72), 5i (75), 5j (65) and 5k
(70%).
Transformation of 1-methyl-3,6-diphenylpyrimido[5,4-e][1,2,4]-
triazine-5,7(1H,6H)-dione 5h (toxoflavin type) into 8-methyl-
3,6-diphenylpyrimido[5,4-e][1,2,4]triazine-5,7(6H,8H)-dione 7h
( fervenulin type)
A stirring mixture of toxoflavin analogue 5h6 (0.66 g, 2.1 mmol),
methyl iodide (1.42 g, 10.0 mmol) and anhydrous potassium
carbonate (0.7 g, 5.1 mmol) in DMF (50 cm3) was heated at
140 ЊC for 2 hours. After cooling, the precipitated potassium
carbonate was filtered off and the filtrate was concentrated in
vacuo. A solution of the residue in water (100 cm3) was
extracted with ethyl acetate (3 × 30 cm3) and the combined
extracts were dried over anhydrous MgSO4. Then the extract
Method C. The same alkylations of reumycin 6a or 6b (2.0
mmol), with sodium hydrogen carbonate (0.34 g, 4.0 mmol)
instead of anhydrous potassium carbonate, as method A
afforded the corresponding toxoflavin derivatives 5a (88), 5b
(86), 5c (76), 5d (81), 5h (77), 5i (76), 5j (82) and 5k (78%).
J. Chem. Soc., Perkin Trans. 1, 2001, 130–137
135

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Fervenulin derivatives 7a–d,h–k; general procedure. Method D.
To reumycin 6a or 6b (2.0 mmol) and anhydrous potassium
carbonate (0.55 g, 4.0 mmol) in 1,4-dioxane or DMF (50 cm3)
was added an appropriate alkyl iodide (10.0 mmol) and the
stirring mixture was heated at 120 or 140 ЊC for 2 hours. After
the same work-up as noted in method A, a recrystallisation
of the crude crystals gave the corresponding pure fervenulin
derivatives 7a,b,h,i as shown in Tables 1 (runs 3, 6, 19 and 22),
2 and 3.
Method E. The same alkylations of reumycin 6a or 6b (2.0
mmol), in DMF (50 cm3) instead of in 1,4-dioxane, as method A
afforded the corresponding fervenulin derivatives 7a–d,h–k as
shown in Tables 1 (runs 2, 5, 8, 10, 18, 21, 24 and 26), 2 and 3.
Transalkylation from toxoflavin derivatives (5a–o) into DMF
(dealkylation of toxoflavin derivatives). A stirring solution of
an appropriate 3-phenyltoxoflavin derivatives 5a–g (3.0 mmol)
in DMF (10 cm3) was heated at 140 ЊC for 3 hours. After
heating, the solution was evaporated in vacuo and the residue
was recrystallised from EtOH or 40% aqueous 1,4-dioxane
to afford the corresponding 3-phenylreumycin 6a or starting
materials 5e–g in high yields as shown in Table 4 (runs 1–4
and 9–11). On the other hand, in the reaction of 3,6-diphenyl-
toxoflavin derivatives 5h–o in the same reaction conditions,
the reaction residue evaporated was triturated with a small
amount of ethanol or 1,4-dioxane to isolate the corresponding
3,6-diphenylreumycin derivative 6b or starting materials 5l–o
(runs 5 and 12–15). In the case of no single compound being
obtained, the residue was subject to column chromatography
to isolate the corresponding 3,6-diphenylreumycin derivative 6b
and starting materials 5i–k, respectively (runs 6–8).
Regioselective alkylation of reumycin derivatives 6a,b by
secondary alkylating agents
Toxoflavin derivatives 5e–g,l–n; general procedure. Method F.
To reumycin 6a or 6b (2.0 mmol) and anhydrous potassium
carbonate (0.55 g, 4.0 mmol) in 1,4-dioxane (50 cm3) was added
an appropriate cyclopentyl bromide, cyclohexyl bromide or 2-
bromopropane (6.0 mmol) and the stirring mixture was heated
under reflux at 120 ЊC for 3–5 hours. After the same work-up as
noted in method A, recrystallisation of the crude crystals gave
the corresponding pure toxoflavin derivatives 5e–g,l–n as shown
in Tables 1 (runs 11, 13, 15, 27, 29 and 31), 2 and 3.
Method G. To reumycin 6a or 6b (2.0 mmol) and 60%
sodium hydride (oil dispersion, 0.16 g, 4.0 mmol) in 1,4-dioxane
(50 cm3) was added an appropriate cyclopentyl bromide,
cyclohexyl bromide or 2-bromopropane (6.0 mmol) and the
mixture was stirred at room temperature for 10–24 hours. After
the same work-up as noted in method B, recrystallisation
of the crude crystals gave the corresponding pure toxoflavin
derivatives 5e (73), 5f (73), 5g (83), 5l (76), 5m (79) and 5n
(76%).
Transalkylation from toxoflavin derivatives (5d–g,k–o) into n-
butylamine (dealkylation of toxoflavin derivatives). A stirring
solution of an appropriate toxoflavin derivative 5d–g,k–o
(3.0 mmol) with n-butylamine (1.0 cm3) in 1,4-dioxane (10.0
cm3) was heated at 100 ЊC for one hour. After heating, the
solution was evaporated in vacuo and the residue was triturated
with EtOH to afford the corresponding reumycin derivatives
6a,b in high yields as shown in Table 4 (runs 16–23). In the
case of the reaction of 1-tert-butyltoxoflavin derivative 5o,
the residue was subject to column chromatography to isolate
the reumycin derivative 6b and starting material 5o (run 24).
Acknowledgements
We are grateful to the SC-NMR Laboratory of Okayama
University for 200 MHz proton NMR experiments. We also
thank Mr T. Fujita for his skillful technical assistance.
Method H. The same alkylations of reumycin 6a or 6b (2.0
mmol) with sodium hydrogen carbonate (0.34 g, 4.0 mmol)
instead of anhydrous potassium carbonate as the method F
afforded corresponding toxoflavin derivatives 5e (81), 5f (80),
5g (87), 5l (78), 5m (76) and 5n (83%).
References
1 A. G. van Veen and J. K. Baars, Proc. Akad. Wet. (Amsterdam),
1937, 40, 498; R. A. Machlowitz, W. P. Fisher, B. S. McKay,
A. A. Tytell and J. Charney, Antibiot. Chemother., 1954, 4, 259.
2 C. DeBoer, A. Dietz, J. S. Evans and R. M. Michael, Antibiot.
Annu., 1959–1960, 220; K. Tanabe, Y. Asahi, M. Nishikawa,
T. Shima, Y. Kuwada, T. Kanzawa and K. Ogata, Takeda Kenkyusho
Nempo., 1963, 22, 133 (Chem. Abstr., 1964, 60, 13242).
Fervenulin derivatives 7e–g,l–n; general procedure. Method I.
To reumycin 6a or 6b (2.0 mmol) and anhydrous potassium
carbonate (0.55 g, 4.0 mmol) in DMF (50 cm3) was added
an appropriate cyclopentyl bromide, cyclohexyl bromide or 2-
bromopropane (6.0 mmol) and the stirring mixture was heated
at 140 ЊC for 3–5 hours. After the same work-up as noted
in method A, recrystallisation of the crude crystals gave the
corresponding pure fervenulin derivatives 7e,g,l,n as shown in
Tables 1 (runs 12, 16, 28 and 32), 2 and 3. In the case of the
reaction with cyclohexyl bromide as an alkylating agent, the
residue obtained by concentration of the extract in vacuo was
subject to column chromatography to isolate the correspond-
ing pure toxoflavin derivatives 5f,m and fervenulin derivatives
7f,m from the mixture of two products, respectively, as shown in
Tables 1 (runs 14 and 30), 2 and 3.
3 S. E. Esipov, M. N. Kolosov and L. A. Saburova, J. Antibiot., 1973,
26, 537.
4 G. D. Daves, Jr., R. K. Robins and C. C. Cheng, J. Am. Chem. Soc.,
1961, 83, 3094; G. D. Daves, Jr., R. K. Robins and C. C. Cheng,
J. Org. Chem., 1961, 26, 5256; G. D. Daves, Jr., R. K. Robins and
C. C. Cheng, J. Am. Chem. Soc., 1962, 84, 1724; F. Yoneda,
K. Shinomura and S. Nishigaki, Tetrahedron Lett., 1971, 851;
E. C. Taylor and F. Sowinsky, J. Org. Chem., 1975, 40, 2321;
T. Nagamatsu, H. Yamasaki and F. Yoneda, Heterocycles, 1994,
37, 1147.
5 S. M. Navashin, I. N. Fomina, T. G. Terent’eva and L. A.
Shtegel’man, Aktual. Vopr. Sovrem. Onkol., 1973, 273 (Chem.
Abstr., 1974, 81, 94f); V. K. Akimenko, N. P. Golovchenko and
T. G. Terent’eva, Antibiotiki (Moscow), 1974, 19, 1101 (Chem.
Abstr., 1975, 82, 132839h); V. K. Akimenko, N. P. Golovchenko
and A. G. Medentsev, Mikrobiologiya, 1974, 43, 839 (Chem.
Abstr., 1975, 82, 107661m); G. G. Egorenko, L. A. Shtegel’man,
V. N. Solov’ev, E. K. Berezina, V. V. Berezhinskaya, M. A. Bykova,
G. V. Dolgova and A. A. Firsov, Antibiotiki (Moscow), 1976,
21, 178 (Chem. Abstr., 1976, 84, 130304x); S. M. Navashin, L. P.
Ivanitskaya, T. G. Terent’eva and L. V. Egorov, Farmatsiya
(Moscow), 1981, 30, 55 (Chem. Abstr., 1981, 95, 73566k); A. A.
Firsov, S. V. Geodakyan, M. R. Lichinitser and V. Ya. Shutka,
Antibiot. Med. Biotekhnol., 1985, 30, 604 (Chem. Abstr., 1985, 103,
189153m).
Regioselective alkylation of reumycin derivatives 6b by tertiary
alkylating agent
1-tert-Butyl-3,6-diphenylpyrimido[5,4-e][1,2,4]triazine-5,7-
(1H,6H)-dione (toxoflavin derivative) 5o. Method J. To reumycin
6b (0.635 g, 2.0 mmol) and anhydrous potassium carbonate
(0.55 g, 4.0 mmol) in 1,4-dioxane (50 cm3) was added 2-bromo-
2-methylpropane (0.82 g, 6.0 mmol) and the stirring mixture
was heated under reflux at 120 ЊC for 7 hours. After the same
work-up as noted in method A, recrystallisation of the crude
crystals afforded the corresponding pure 1-tert-butyltoxoflavin
derivative 5o as shown in Tables 1 (run 33), 2 and 3. In the case
of the same reaction in DMF as the solvent, no alkylation
product was obtained as shown in Table 1 (run 34).
6 T. Nagamatsu, H. Yamasaki, T. Hirota, M. Yamato, Y. Kido,
M. Shibata and F. Yoneda, Chem. Pharm. Bull., 1993, 41, 362.
7 F. Yoneda and T. Nagamatsu, Chem. Pharm. Bull., 1975, 23, 2001;
F. Yoneda and T. Nagamatsu, Synthesis, 1975, 177; F. Yoneda
and T. Nagamatsu, Chem. Pharm. Bull., 1975, 23, 1885; F. Yoneda,
136
J. Chem. Soc., Perkin Trans. 1, 2001, 130–137

View Article Online
T. Nagamatsu and K. Shinomura, J. Chem. Soc., Perkin Trans. 1,
1976, 713; F. Yoneda, Y. Sakuma, T. Nagamatsu and S. Mizumoto,
J. Chem. Soc., Perkin Trans. 1, 1976, 2398.
11 F. Yoneda and T. Nagamatsu, Tetrahedron Lett., 1973, 1577; F.
Yoneda and T. Nagamatsu, J. Heterocycl. Chem., 1974, 11, 271;
F. Yoneda and T. Nagamatsu, Bull. Chem. Soc. Jpn., 1975, 48, 2884.
12 T. Nagamatsu and H. Yamasaki, Heterocycles, 1997, 45, 643.
13 T. Nagamatsu, Jpn. Kokai Tokkyo Koho, JP 07 41,479/1995
(Chem. Abstr., 1995, 123, 55928x).
14 T. K. Liao, F. Baiocchi and C. C. Cheng, J. Org. Chem., 1966, 31,
900.
8 T. Nagamatsu, Y. Yamagishi and F. Yoneda, Jpn. Kokai Tokkyo
Koho, JP 09 255,681/1997 (Chem. Abstr., 1997, 127, 336635w).
9 M. Ozasa, T. Amakusa and T. Nagamatsu, Jpn. Kokai Tokkyo Koho,
JP 10 175,807/1998 (Chem. Abstr., 1998, 129, 64309x).
10 F. Yoneda and T. Nagamatsu, J. Am. Chem. Soc., 1973, 95, 5735;
F. Yoneda, T. Nagamatsu and M. Ichiba, J. Heterocycl. Chem., 1974,
11, 83.
15 F. Yoneda, M. Kawamura, T. Nagamatsu, K. Kuretani, A. Hoshi
and M. Iigo, Heterocycles, 1976, 4, 1503.
J. Chem. Soc., Perkin Trans. 1, 2001, 130–137
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