Synthesis and anti-oomycete activity of novel quinazolin- and benzothiazol-6-yloxyacetamides: Potent aza-analogs and five-ring analogs of quinoline fungicides

Article abstract of DOI:10.1016/j.bmc.2015.08.009

Novel quinazolin- and benzothiazol-6-yloxyacetamides show excellent in vivo activity against the three economically most important Oomycete pathogens Phytophthora infestans, Plasmopara viticola and Pythium ultimum. They are polar analogs of known quinolin-6-yloxyacetamides, which are not active against the soil-borne damping-off disease caused by Pythium ultimum. The Bogert quinazoline synthesis, an almost forgotten heterocyclization technique, proved to be highly useful for the concise construction of required quinazolin-6-ol building blocks.

Full text of DOI:10.1016/j.bmc.2015.08.009

Bioorganic & Medicinal Chemistry xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and anti-oomycete activity of novel quinazolin- and
benzothiazol-6-yloxyacetamides: Potent aza-analogs and five-ring
analogs of quinoline fungicides
a
a
a
a,
⇑
Renaud Beaudegnies , Laura Quaranta , Fiona Murphy Kessabi , Clemens Lamberth
,
a
b
Gertrud Knauf-Beiter , Torquil Fraser
a
Syngenta Crop Protection AG, Chemical Research, Schaffhauserstr. 101, CH-4332 Stein, Switzerland
Syngenta Ltd, Jealott’s Hill International Research Centre, Bracknell, Berkshire RG42 6EY, United Kingdom
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel quinazolin- and benzothiazol-6-yloxyacetamides show excellent in vivo activity against the three
economically most important Oomycete pathogens Phytophthora infestans, Plasmopara viticola and
Pythium ultimum. They are polar analogs of known quinolin-6-yloxyacetamides, which are not active
against the soil-borne damping-off disease caused by Pythium ultimum. The Bogert quinazoline synthesis,
an almost forgotten heterocyclization technique, proved to be highly useful for the concise construction
of required quinazolin-6-ol building blocks.
Received 30 June 2015
Revised 30 July 2015
Accepted 12 August 2015
Available online xxxx
Keywords:
Ó 2015 Elsevier Ltd. All rights reserved.
Quinazoline
Benzothiazole
Heterocycle
Fungicide
Crop protection
1
. Introduction
Recently we have published the synthesis and structure–activ-
against the later pathogen, Pythium ultimum, because of enhanced
systemicity which seems to be required for the efficient control of
this soil-borne disease. In this paper we summarize the results of
our investigation of synthesis, phys–chem properties and struc-
ture–activity relationships of novel quinazolin-6-yloxyacetamides,
such as 2, and 1,3-benzothiazol-6-yloxyacetamides, such as 3 as
potent aza-analogs or five-ring analogs of quinolin-6-yloxyac-
etamide fungicides, such as 1 (Fig. 1).
1
ity relationship of quinolin-6-yloxyacetamides. The members of
this novel class of experimental fungicides exhibited excellent con-
trol of a whole range of phytopathogens from the group of
Ascomycetes and Oomycetes. Their fungicidal activity is due to
their ability to inhibit the fungal tubulin polymerization, leading
to microtubule destabilization. In our continued search for new
2
fungicides with potent anti-oomycete activity we have found, that
2
2
2
. Results and discussion
.1. Synthesis
analogs in which the pyridine moiety of quinolin-6-yloxyac-
etamides such as 1 has been replaced by a pyrimidine (?2) or a
thiazole ring (?3), show excellent activity against the three eco-
nomically most important Oomycete diseases. These include the
foliar diseases potato late blight (caused by Phytophthora infestans)
and grape downy mildew (resulting from Plasmopara viticola as
causal agent) as well as the soil-borne damping-off disease of sev-
eral different crops (for which Pythium ultimum is responsible). As
there are numerous examples known in which replacement of ring
carbon atoms by heteroatoms can lead to improved water solubil-
.1.1. Quinazolines
The trisubstituted heterobicyclic scaffold of the lead structure 1
9
had been prepared by a Skraup-type quinoline synthesis, which is
not applicable to the quinazoline core, therefore we had to look for
a different approach. For the synthesis of the 8-unsubstituted
quinazolines, such as 2, we decided to apply Bogert’s quinazoline
1
0–12
synthesis
-hydroxyquinazoline (7) from inexpensive 3-hydroxybenzalde-
hyde (4) (Scheme 1). This quinazoline synthesis, which is not found
as it allowed us to obtain the required intermediate
3
–8
ity,
it does not come by surprise that increasing the number of
6
heteroatoms in our bicyclic scaffold results in higher efficacy
1
2
very often in the literature, starts with the regioselective nitra-
tion to deliver 5. This disubstituted benzaldehyde is then con-
verted with formamide under a hydrogen chloride gas stream
⇑
Corresponding author. Tel.: +41 62 866 0224; fax: +41 62 866 0860.
E-mail address: clemens.lamberth@syngenta.com (C. Lamberth).
http://dx.doi.org/10.1016/j.bmc.2015.08.009
968-0896/Ó 2015 Elsevier Ltd. All rights reserved.
0
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2
R. Beaudegnies et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
O
reduction and ether cleavage delivered the desired 6-hydroxy-8-
O
methyl-6-hydroxyquinazoline 19. The finalization of the synthesis
is achieved by using the same last three steps as already applied
for the preparation of 2 in Scheme 1, which are alkylation of the
phenol function to 20, ester saponification to 21 and amide
coupling, delivering 22, the 8-methylated analog of 2 (Scheme 2).
N
H
S
N
1
typical example of quinolin-6-yloxy-
acetamide lead compounds
O
O
2.1.2. Benzothiazoles
O
S
O
For the synthesis of 4-chlorobenzothiazol-6-yloxyacetamides,
such as 3, we chose 2-chloro-4-methoxyaniline (23) as starting
material, which could be cyclized to the 2-aminobenzothiazole
derivative 24 upon treatment with potassium thiocyanate and bro-
mine. This standard 2-aminobenzothiazole synthesis proceeds via
N
N
H
N
H
S
S
N
N
Cl
2
3
quinazolin-6-yloxyacetamide analog
benzothiazol-6-yloxyacetamide analog
Figure 1. Fungicidally active quinazolin- and benzothiazol-6-yloxyacetamides 2
and 3 and their lead structure 1.
an ortho-thiocyanato-aniline intermediate, which undergoes ring
16–18
closure by reaction with bromine.
For the following deamina-
1
9,20
tion we applied Chedekel’s conditions
with sodium nitrite and
phosphinic acid. The ether cleavage of the resulting methoxy-sub-
stituted benzothiazole 25 delivered the desired 4-chloro-6-hy-
droxybenzothiazole 26. Again the same last three steps as in
0
into the N,N -diformylated aminal 6, which undergoes reductive
cyclization by treatment with zinc in acetic acid to deliver directly
the desired building block 7. Its hydroxyl function can be easily
Schemes 1 and 2, alkylation with an
a-chlorocarboxylate to 27,
alkylated with
yloxyacetamides 8 and 10 bearing either an ethyl or a thiomethyl
group at the -carbon atom of the ester. These two functionalities
a-halocarboxylates leading to the quinazolin-6-
ester saponification to 28 and finally amidation afforded the ben-
zothiazol-6-yloxyacetamide 3 (Scheme 3).
a
played already the biggest role during the optimization of the
quinolin-6-yloxyacetamide lead compounds, such as 1. It is note-
1
2.2. Structure–activity relationship
worthy that this alkylation reaction introduces completely differ-
ent functional groups under the same reaction conditions, as the
hydroxyl function of 7 has been transformed into an ether (?8)
as well as into a O,S-acetal (?10). The saponification of the ester
function in 8 and 10 to the corresponding carboxylic acids and
their further conversion with 1,1-dimethylpropargylamine and
2
.2.1. Influence of the physico-chemical properties on the
Pythium activity
Some of the quinoline lead compounds, such as 1, showed use-
ful activity against the foliar Oomycete diseases Phytophthora infes-
tans and Plasmopara viticola. However, their strength was clearly
powerful efficacy against plant pathogens from the Ascomycetes
genus, especially leaf spot diseases such as wheat leaf blotch
caused by Mycosphaerella graminicola and barley net blotch with
1
,1-dimethyl-2-butynylamine, respectively, under peptide cou-
pling conditions finally led to the fungicidally active amides 2
and 9.
1
Pyrenophora teres as causal agent. This is in stark contrast to the
One of the results of the structure–activity relationship study of
the quinoline lead compound class was that small lipophilic sub-
stituents in ring position 8 often have a positive impact on the
fact that good in vivo activity against the soil-borne Oomycete
pathogen Pythium ultimum was never observed with quinolin-6-
yloxyacetamides. A major reason for this spectrum gap is probably
their lipophilicity, as a requirement for efficient Pythium control is
a certain degree of systemicity, driven by low logP and high water
solubility values. Because we had been looking for a solution
against all three economically Oomycete pathogens Phytophthora
infestans, Plasmopara viticola and Pythium ultimum, we decided to
design close analogs of the fungicidally active quinolin-6-yloxyac-
etamides with improved physico-chemical properties. Table 1
compares the Pythium activity, logP values and water solubility
of four different compounds, which are all linked via the same O,
S-acetal to the same N-alkynylated amide. Although the two
quinoline derivatives (entries 1 and 2) bearing iodo and ethynyl
1
fungicidal activity. In this regard halogens atoms and the methyl
group were of particular interest. As the disubstituted anthranilic
acid 12 was available in larger amounts, we decided to approach
8
-methylquinazolin-6-yloxyacetamides such as 22 via
a
13,14
Niementowski synthesis.
First we had to transfer 3-methyl-
5
-iodoanthranilic acid (12) via esterification to 13, amine
protection to 14, methoxylation to 15 and deprotection to the
disubstituted methyl anthranilate 16. Under the conditions of
1
5
Leonard’s variation of the Niementowski quinazoline synthesis,
which uses an amidine as coupling partner instead of the
Niementowski-typical amide, the quinazolinone 17 was formed.
Three further manipulations, the chlorination to 18, subsequent
O
O
O
H
NH
O
O
HCONH
HCl
2
,
Zn,
ClCH(Et)CO
2
Me,
HO
HO
HO
OH
O
HNO
3
AcOH
K
2
CO
3
H
H
N
H
N
N
O
H
25 %
73 %
96 %
65 %
NO
2
NO
N
N
2
4
5
6
7
8
1
. NaOH
2
ClCH(SMe)CO Me,
K CO
2 3
61 %
55 % 2. H NC(Me)
2
2
C
CH
3
HOAt, EDCI, NEt
O
O
O
O
H
2
NC(Me)
2
C
CCH
3
3
O
O
O
O
N
N
N
H
HOAt, EDCI, NEt
N
OH
NaOH
97 %
N
O
N
H
S
S
S
N
58 %
N
N
N
2
11
10
9
Scheme 1. Synthesis of the fungicidally active quinazolin-6-yloxyacetamides 2 and 9.
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R. Beaudegnies et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
3
O
O
O
N
O
N
MeCOCH
2
CH
2
COMe,
Na, Cu,
MeOH
I
I
I
O
OH TMSCHN
2
O
APTS
O
O
99 %
NH2
84 %
62 %
NH2
12
13
14
15
H
2
NOH.HCl,
45 %
NEt
3
Cl
O
O
1
. H
2
, Pd/C, NEt
3
3
POCl ,
PhNMe
OH
O
O
O
N
2. BBr
3
N
2
N
2
HC(=NH)NH .OAc
O
70 %
99 %
86 %
N
N
N
H
NH
2
19
18
17
16
ClCH(SMe)CO
2
Me,
62 %
2 3
K CO
O
O
O
H
2
NC(Me)
2
C
CCH
3
O
O
O
S
N
O
NaOH
79 %
N
OH
HOAt, EDCI, NEt
3
N
N
H
S
S
79 %
N
N
N
20
21
22
Scheme 2. Synthesis of the fungicidally active quinazolin-6-yloxy acetamide 22.
KSCN,
Br
1. NaNO
PO
PO
2
,
2
,
H
3
3
O
S
N
O
O
S
N
OH
AcOH
2. H
3
2
S
N
BBr
3
H N
2
48 %
94 %
2
H N
36 %
Cl
Cl
Cl
Cl
25
26
23
24
ClCH(SMe)CO
2
Me,
81 %
K
2
CO
3
O
O
O
H
2
NC(Me)
2
C
CCH
3
O
S
O
S
O
S
N
HOAt, EDCI, NEt
NaOH
91 %
O
N
H
3
OH
S
S
S
77 %
N
N
Cl
Cl
Cl
28
27
3
Scheme 3. Synthesis of the fungicidally active benzothiazol-6-yloxyacetamide 3.
groups were two of the best possible substituents in position 3
against Ascomycetes species,1 they are inactive in our standard
in vivo Pythium assay and also in the in vitro Pythium test.
Table 1 shows that they are certainly weaker than the correspond-
ing quinazoline and benzothiazole derivatives (entries 3 and 4).
This clearly correlates with the higher polarity of the quinazoline
and the benzothiazole, demonstrated by the lower logP value
and the much higher water solubility compared to the similar
quinolines.
benzothiazoles with a methyl or chloro substituent in positions 2
or 4. In addition the impact of replacing the acetamide linker with
a thiomethyl or ethyl substituent was investigated. The in vivo
results for the whole set of compounds with the same dimethylbu-
tynylamine moiety against the three mentioned Oomycete dis-
eases are summarized in Table 2. The mentioned values show the
activity at rather low use rates, for Phytophthora infestans and
Plasmopara viticola at 60 ppm (corresponding to only 60 g/ha), for
Pythium ultimum at 20 ppm. As a general trend, the benzothiazole
derivatives appear to be stronger than the corresponding quinazo-
line derivatives, Another trend is that compounds with an ethyl
group in the acetamide linker (entries 3 and 9) are clearly weaker
than their counterparts with a thiomethyl group in the same posi-
tion (entries 1 and 4). Whereas a methyl or chloro substituent in
quinazoline position 8 and benzothiazole position 4 seems to deli-
ver a better overall activity across all three pathogens (entries 2, 6
and 7), remarkably, a chloro or methyl substituent at the ring car-
bon between both benzothiazole heteroatoms (position 2) com-
pletely destroys the activity (entries 5 and 10). Another notable
manipulation which leads to full loss of activity is the oxidation
of the thiomethyl group in the acetamide linker to a sulfoxide func-
tion (entry 8) (Table 2).
2
.2.2. Influence of the substitution pattern on the anti-
oomycete activity
After we had confirmed the superiority of quinazolines and
benzothiazoles in the control of Pythium compared to correspond-
ing quinoline derivatives, we wanted to check their potency
against the two other Oomycete diseases Phytophthora infestans
and Plasmopara viticola. Furthermore we wanted to acquire infor-
mation about the influence of different substituents on the fungici-
dal activity. Based on the structure–activity relationship
1
experience with the quinolin-6-yloxyacetamides, we focused
mainly on unsubstituted quinazolines as well as on benzothiazoles
and quinazolines with a methyl group in position 8 and on
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4
R. Beaudegnies et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
Table 1
3
Unity 400 spectrometer at 400 MHz using CDCl as solvent and
Influence of the physico-chemical properties on the Pythium activitya
tetramethylsilane as internal standard. Chemical shifts are
reported in ppm downfield from the standard (d = 0.00), coupling
constants in Hz. LC–MS spectra were determined using the follow-
ing apparatus: ACQUITY UPLC from Waters, Phenomenex Gemini
C18, 3 mm particle size, 110 Angström, 30 ꢀ 3 mm column,
O
O
R
N
H
O
S
1
.7 mL/min, 60 °C, H
2
3
O + 0.05% HCOOH (95%)/CH CN/MeOH 4:1
Entry
R
Pythium
ultimum
Pythium
LogP Water
solubility
ultimum
(damping-
off
disease)
Pouch
3
+ 0.04% HCOOH (5%)—2 min—CH CN/MeOH 4:1 + 0.04% HCOOH
(
damping-
(ppm)
(5%)—0.8 min; ACQUITY SQD Mass Spectrometer from Waters, ion-
ization method: electrospray (ESI), Polarity: positive ions, Capillary
off disease)
Liquid
culture
(
(
kV) 3.00, Cone (V) 20.00, Extractor (V) 3.00, Source Temperature
°C) 150, Desolvation Temperature (°C) 400, Cone Gas Flow (L/Hr)
(
in vitro)
(in vivo)
6
0, Desolvation Gas Flow (L/Hr) 700. Analytical thin-layer
I
chromatography (TLC) was performed using silica gel 60 F524
precoated plates. Preparative flash chromatography was per-
formed using silica gel 60 (40–63 lm, E. Merck). Unless otherwise
stated, all reactions were carried out under anhydrous conditions
in an inert atmosphere (nitrogen or argon) with dry solvents.
1
2
20
0
0
3.99
3.45
2.5
12
N
HC
70
80
N
N
3
4
70
50
1.92
2.52
1139
211
4.1.1. 5-Hydroxy-2-nitrobenzaldehyde (5)
N
S
3
-Hydroxybenzaldehyde (21 g, 0.17 mol) were slowly added to
2
00 ml of 28% nitric acid. Subsequently the mixture was neutral-
100
N
ized with aqueous sodium hydroxide solution and stirred for 1 h
at room temperature. The resulting yellow precipitate was filtered
and then dissolved in 150 ml of benzene. This mixture was heated
to reflux for 30 min and then cooled down to room temperature.
The insoluble material was recovered by filtration and recrystal-
lized from water to deliver (5, 7.0 g, 42 mmol, 25%) as yellow
crystals. Mp, 167–168 °C. H NMR (CDCl
a
Results are given in % activity at 6 ppm for the in vitro assay and at 20 ppm for
the in vivo assay against Pythium ultimum.
3
. Conclusions
1
3
): d = 6.16 (br s, 1H),
The introduction of an additional heteroatom into the heterobi-
7
.13 (dd, 1H), 7.29 (d, 1H), 8.16 (d, 1H), 10.48 (s, 1H). LC–MS:
+
cyclic core of quinolin-6-yloxyacetamides opens new avenues for
the control of foliar and soil-borne Oomycete diseases, as the
resulting quinazoline and benzothiazole analogs offer in addition
to good activity against Phytophthora infestans and Plasmopara viti-
cola also in vivo potency against Pythium ultimum. Their improved
physico-chemical properties seem to play a key role in favouring
this latter activity. Simple benzaldehydes, such as 4, and anilines,
such as 23, can be employed as starting materials for the synthesis
of the hydroxylated quinazoline and benzothiazole building blocks
Rt = 1.33 min; MS: m/z = 168 [M+1] .
4
.1.2. N-[Formamido-(5-hydroxy-2-nitrophenyl)methyl]for-
mamide (6)
A stream of hydrogen chloride gas was bubbled through a light
yellow suspension of 5-hydroxy-2-nitrobenzaldehyde (5, 6.7 g,
4
0 mmol) in 25 ml of formamide under stirring at room tempera-
ture. The temperature rose rapidly after starting the addition of
hydrogen chloride and an orange solution formed when the tem-
perature reached 50 °C. When the temperature reached 80 °C
1
0–12
7
and 26. For this purpose the Bogert quinazoline synthesis,
a
relatively underutilized heterocyclization reaction, seems to offer
greater practicality than the more well-known Niementowski
quinazoline synthesis, because it starts from anilines, which are
usually abundantly available, instead of anthranilic acids. The last
three steps of the reaction sequence to 2 and 3 (alkylation of phe-
nol, ester saponification and amidation) are in analogy to the
already described quinolin-6-yloxyacetamides.
In summary, a structure–activity relationship study revealed
similarities of the novel quinazolin- and benzothiazol-6-yloxyac-
etamides to the related quinoline derivatives. Compounds with a
(
20 min after initializing the gas flow), crystals started to precipi-
tate. After the reaction temperature reached 90 °C, it was kept at
this level with the help of external cooling. After cooling the reac-
tion mixture for 30 min, the reaction temperature began to fall
down when the cooling was stopped. The gas flow was turned
off, the reaction mixture was allowed to cool down to room
temperature and diluted with ice-water and treated with 30%
aqueous sodium hydroxide solution until a pH value of 4 was
reached. The resulting suspension was filtered, the solid
residue was washed with water and dried to deliver
thiomethyl substituent at the
a-carbon atom of the acetic acid
N-[formamido-(5-hydroxy-2-nitrophenyl)methyl]formamide (6,
1
moiety are more active than the corresponding ethyl-substituted
analogs. Quinazolines and benzothiazoles with a methyl or halogen
substituent in positions 8 and 4, respectively, show better activity
against all three important Oomycete diseases than the comparable
unsubstituted analogs. Especially notable is the 4-methyl
analog of 3 (entry 7 of Table 2) which delivers very strong in vivo
activity against all three Oomycete diseases at low application
rates.
7
.0 g, 29 mmol, 73%) as yellowish crystals. Mp, 239–240 °C.
NMR (DMSO-d
.92–8.01 (m, 2H), 8.88 (d, 1H), 10.99 (br s, 1H). LC–MS:
H
6
): d = 6.85 (t, 1H), 6.97 (s, 1H), 7.06 (t, 1H),
7
+
+
Rt = 1.18 min; MS: m/z = 241 [M+1] , 242 [M+2] .
4
.1.3. Quinazolin-6-ol (7)
0 ml of acetic acid were added dropwise to a suspension of
N-[formamido-(5-hydroxy-2-nitrophenyl)methyl] formamide (6,
.8 g, 20 mmol) and zinc powder (15 g, 0.23 mol) in 75 ml of
2
4
4
4
. Experimental section
.1. Chemistry
crushed ice. The reaction mixture was stirred for 30 min, then
additional zinc powder (5.8 g, 90 mmol) was added portionwise.
During this addition the reaction temperature rose to 30 °C. The
reaction mixture was stirred for 3 h at room temperature. The
resulting grey suspension was filtered through celite. The filtrate
was neutralized by addition of solid sodium bicarbonate and
All new compounds were characterized by standard spectro-
1
scopical methods. H NMR spectra were recorded on a Varian
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R. Beaudegnies et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
5
Table 2
Influence of the substitution pattern on the anti-oomycete activity
a
O
R
N
H
Entry
R
Phytophthora infestans
Plasmopara viticola
Pythium ultimum
(
potato late blight)
(grape downy mildew)
(damping-off disease)
O
O
N
1
2
(2)
74
80
50
24
S
S
N
N
CH3
CH3
N
N
(22)
94
0
100
CH3
O
3
4
5
50
100
0
55
0
N
CH3
O
S
100
0
S
N
CH3
O
S
N
Cl
0
S
CH3
O
O
S
N
6
7
(3)
S
S
99
100
100
20
80
CH3
CH3
Cl
S
N
100
CH3
O
S
N
S
N
8
9
1
0
35
0
0
80
0
0
18
0
S
O
O
CH3
CH3
O
S
N
H C
0
3
CH3
a
Results are given in % activity at 60 ppm for Phytophthora infestans and Plasmopara viticola and at 20 ppm for Pythium ultimum.
extracted with a 95:5 mixture of ethyl acetate and methanol. The
combined organic layer was dried over magnesium sulfate and
4.1.5. N-(1,1-Dimethylprop-2-ynyl)-2-quinazolin-6-yloxy-butana-
mide (9)
evaporated to directly deliver quinazolin-6-ol (7, 2.8 g, 19 mmol,
A solution of methyl 2-quinazolin-6-yloxybutanoate (8, 1.5 g,
6.1 mmol) in 30 ml of ethanol was treated with 4.6 ml of a 2 N
solution of sodium hydroxide in water. The reaction mixture was
stirred for 1 h at room temperature, then poured on ice-water
and acidified to pH 2 by addition of 2 N hydrochloric acid. The
mixture was extracted with ethyl acetate, the organic layer was
washed with water and brine, dried over magnesium sulfate and
evaporated under reduced pressure to deliver 2-quinazolin-6-
yloxybutanoic acid. 1,1-Dimethylprop-2-ynylamine (0.34 g,
4.1 mmol) was dissolved in 30 ml of N,N-dimethylformamide and
triethylamine (0.41 g, 4.1 mmol), 1-hydroxy-7-azabenzotriazole
(0.55 g, 4.1 mmol), 1-ethyl-3-(3-dimethylaminopropyl) carbodi-
imide (0.78 g, 4.1 mmol) and the above prepared 2-quinazolin-6-
yloxybutanoic acid (0.95 g, 4.1 mmol) were added consecutively.
The reaction mixture was stirred for 20 h at room temperature,
then poured on saturated aqueous sodium bicarbonate solution
and extracted with ethyl acetate. The organic layer was dried over
magnesium sulfate and evaporated under reduced pressure, the
residue was purified by chromatography on silica gel, using ethyl
acetate and heptane as eluents to deliver N-(1,1-dimethylprop-2-
ynyl)-2-quinazolin-6-yloxy-butanamide (9, 1.0 g, 3.4 mmol, 55%).
1
9
6%). H NMR (DMSO-d
6
): d = 7.23 (d, 1H), 7.51 (dd, 1H), 7.82 (d,
1
H), 9.01 (s, 1H), 9.40 (s, 1H), 10.56 (br s, 1H). LC–MS:
+
Rt = 1.38 min; MS: m/z = 147 [M+1] .
4
.1.4. Methyl 2-quinazolin-6-yloxybutanoate (8)
Potassium carbonate (8.3 g, 60 mmol) was added to a solution
of quinazolin-6-ol (7, 2.9 g, 20 mmol) in 50 ml of N,N-dimethylfor-
mamide. After the addition of methyl 2-bromobutyrate (4.5 g,
2
5 mmol), the reaction mixture was stirred for 16 h at room
temperature. Subsequently the dark brown mixture was poured
on a cold saturated aqueous solution of sodium bicarbonate and
extracted with ethyl acetate. The organic layer was washed with
water and brine, dried over magnesium sulfate and evaporated
under reduced pressure. The residue was purified by
chromatography on silica gel, using ethyl acetate and heptane as
eluents to yield methyl 2-quinazolin-6-yloxybutanoate (8, 3.2 g,
1
1
3
9
3 mmol, 65%). H NMR (CDCl
3
): d = 1.14 (t, 3H), 2.10 (q, 2H),
.79 (s, 3H), 4.77 (t, 1H), 7.04 (d, 1H), 7.63 (dd, 1H), 8.00 (d, 1H),
.21 (s, 1H), 9.28 (s, 1H). LC–MS: Rt = 1.40 min; MS: m/z = 247
+
[
M+1] .
Please cite this article in press as: Beaudegnies, R.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.08.009

6
R. Beaudegnies et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
1H NMR (CDCl
): d = 1.07 (t, 3H), 1.61 (s, 3H), 1.63 (s, 3H), 2.06 (q,
(br s, 2H), 7.33 (s, 1H), 7.82 (s, 1H). LC–MS: Rt = 1.87 min; MS:
m/z = 292 [M+1] .
3
+
2
1
H), 2.32 (s, 1H), 4.61 (t, 1H), 6.35 (br s, 1H), 7.20 (d, 1H), 7.64 (dd,
H), 8.02 (d, 1H), 9.27 (s, 1H), 9.32 (s, 1H). LC–MS: Rt = 1.48 min;
+
MS: m/z = 298 [M+1] .
4.1.10. Methyl 2-(2,5-dimethylpyrrol-1-yl)-5-iodo-3-methyl-
benzoate (14)
4
(
.1.6. Methyl 2-methylsulfanyl-2-quinazolin-6-yloxyacetate
10)
Methyl 2-chloro-2-(methylsulfanyl)acetate (1.7 g, 11 mmol)
A mixture of methyl 2-amino-5-iodo-3-methyl-benzoate (13,
7.8 g, 27 mmol), acetonylacetone (4.3 g, 37 mmol) and catalytic
amounts of p-toluenesulfonic acid in 125 ml of toluene was heated
to reflux for 18 h, during which forming water was collected with
the aid of a Dean-Stark trap. The reaction mixture was cooled to
room temperature and diluted with aqueous ammonium chloride
solution and ethyl acetate. The phase were separated, the organic
layer was washed with a aqueous ammonium chloride solution,
dried over magnesium sulfate and evaporated under reduced pres-
sure, the residue was purified by chromatography on silica gel,
using ethyl acetate and cyclohexane as eluents to deliver methyl
and milled potassium carbonate (5.0 g, 36 mmol) were consecu-
tively added to a suspension of quinazolin-6-ol (7, 1.0 g, 7.2 mmol)
in 15 ml of N,N-dimethylformamide. The reaction mixture was stir-
red for 4 h at room temperature, then poured on a cold saturated
aqueous solution of sodium bicarbonate and extracted with ethyl
acetate. The organic layer was washed with water, dried over mag-
nesium sulfate and evaporated under reduced pressure. The resi-
due was purified by chromatography on silica gel, using ethyl
acetate and hexane as eluents to deliver methyl 2-methylsul-
2-(2,5-dimethylpyrrol-1-yl)-5-iodo-3-methyl-benzoate (14, 8.3 g,
1
1
fanyl-2-quinazolin-6-yloxyacetate (10, 1.2 g, 4.4 mmol, 61%).
NMR (CDCl
H), 7.70 (dd, 1H), 8.03 (d, 1H), 9.25 (s, 1H), 9.36 (s, 1H). LC–MS:
H
22 mol, 84%). H NMR (CDCl
3
): d = 1.84 (s, 6H), 1.91 (s, 3H), 3.68
3
): d = 2.25 (s, 3H), 3.90 (s, 3H), 5.78 (s, 1H), 7.31 (d,
(s, 3H), 5.87 (s, 2H), 7.82 (d, 1H), 8.05 (d, 1H). LC–MS:
+
1
Rt = 2.14 min; MS: m/z = 370 [M+1] .
+
Rt = 1.36 min; MS: m/z = 265 [M+1] .
4
.1.11. Methyl 2-(2,5-dimethylpyrrol-1-yl)-5-methoxy-3-methyl
4
.1.7. 2-Methylsulfanyl-2-quinazolin-6-yloxy-acetic acid (11)
suspension of methyl 2-methylsulfanyl-2-quinazolin-6-
benzoate (15)
A
Sodium (1.3 g, 56 mmol) was added to a solution of methyl 2-
(2,5-dimethylpyrrol-1-yl)-5-iodo-3-methyl-benzoate (14, 6.9 g,
19 mmol) in 50 ml of methanol. The mixture was stirred for 1 h
at room temperature, then it was diluted with 90 ml of N,N-
dimethylformamide. Copper-bronze (2.4 g, 37 mmol) was added
and the reaction mixture was stirred for 3 h at 130 °C.
Subsequently the mixture was cooled to room temperature and fil-
tered through Celite. The filtrate was washed with aqueous ammo-
nium sulfate solution, the aqueous layer was extracted with ethyl
acetate. The combined organic layer was dried over magnesium
sulfate and evaporated under reduced pressure, the residue was
purified by chromatography on silica gel, using ethyl acetate and
cyclohexane as eluents to deliver methyl 2-(2,5-dimethylpyrrol-
yloxyacetate (10, 1.1 g, 4.1 mmol) in 15 ml of ethanol was treated
with 3.1 ml of a 2 N solution of sodium hydroxide in water. The
reaction mixture was stirred for 1 h at room temperature, then
cooled down to 0 °C, acidified with 2 N hydrochloric acid until
pH 5 was reached and evaporated. The remainder was suspended
in ethanol and stirred for 10 min at 60 °C. The suspension was fil-
tered, the solid residue washed with cold ethanol and dried to deli-
ver 2-methylsulfanyl-2-quinazolin-6-yloxy-acetic acid (11, 1.0 g,
1
4
7
.0 mmol, 97%). H NMR (DMSO-d
6
): d = 2.06 (s, 3H), 5.44 (s, 1H),
.40 (d, 1H), 7.63 (dd, 1H), 7.84 (d, 1H), 9.08 (s, 1H), 9.37 (s, 1H).
LC–MS: Rt = 1.13 min; MS: m/z = 251 [M+1] .
+
4
.1.8. N-(1,1-dimethylbut-2-ynyl)-2-methylsulfanyl-2-
1-yl)-5-methoxy-3-methyl benzoate (15, 3.1 g 11 mol, 62%). 1
NMR (CDCl ): d = 1.87 (s, 6H), 1.92 (s, 3H), 3.66 (s, 3H), 3.87 (s,
H
quinazolin-6-yloxy-acetamide (2)
3
Triethylamine (0.5 g, 5 mmol), 1-hydroxy-7-azabenzotriazole
0.34 g, 2.5 mmol), 1-ethyl-3-(3-dimethylamino-propyl)carbodi-
3H), 5.87 (s, 2H), 6.99 (d, 1H), 7.24 (d, 1H). LC–MS: Rt = 1.97 min;
MS: m/z = 274 [M+1] .
+
(
imide (0.48 g, 2.5 mmol) and 2-methylsulfanyl-2-quinazolin-6-
yloxy-acetic acid (11, 0.62 g, 2.5 mmol) were added consecutively
to a solution of 1,1-dimethylbut-2-yn-1-amine (0.33 g, 2.5 mmol)
in 10 ml of N,N-dimethylformamide. The reaction mixture was stir-
red for 16 h at room temperature, then poured on saturated aque-
ous sodium bicarbonate solution and extracted with ethyl acetate.
The organic layer was dried over magnesium sulfate and evapo-
rated under reduced pressure, the residue was purified by chro-
matography on silica gel, using ethyl acetate and hexane as
4.1.12. Methyl 2-amino-5-methoxy-3-methyl benzoate (16)
A solution of methyl 2-(2,5-dimethylpyrrol-1-yl)-5-methoxy-3-
methyl-benzoate (15, 3.0 g 11 mmol), hydroxylamine hydrochlo-
ride (13 g, 0.19 mol) and triethylamine (3.3 g, 33 mol) in 100 ml
of a 2:1 ethanol/water mixture was irradiated under microwave
conditions for 1 h at 180 °C. Subsequently, the reaction mixture
was cooled and concentrated in vacuo. The remainder was taken
up in water and ethyl acetate, the phases were separated and the
organic layer was washed with brine, dried over magnesium sul-
fate and evaporated under reduced pressure, the residue was puri-
fied by chromatography on silica gel, using ethyl acetate and
eluents to deliver N-(1,1-dimethylbut-2-ynyl)-2-methylsulfanyl-
1
2
-quinazolin-6-yloxy-acetamide (2, 0.48 g, 1.4 mmol, 58%).
NMR (CDCl
H), 6.69 (br s, 1H), 7.37 (d, 1H), 7.68 (dd, 1H), 8.05 (d, 1H), 9.28
H
3
): d = 1.69 (s, 6H), 1.83 (s, 3H), 2.22 (s, 3H), 5.66 (s,
1
(
cyclohexane as eluents to deliver methyl 2-amino-5-methoxy-3-
+
1
s, 1H), 9.36 (s, 1H). LC–MS: Rt = 1.51 min; MS: m/z = 330 [M+1] .
methyl benzoate (16, 900 mg, 5.0 mmol, 45%). H NMR (CDCl
3
):
d = 2.16 (s, 3H), 3.75 (s, 3H), 3.88 (s, 3H), 6.89 (d, 1H), 7.26 (d,
+
4
.1.9. Methyl 2-amino-5-iodo-3-methyl-benzoate (13)
1H). LC–MS: Rt = 1.47 min; MS: m/z = 196 [M+1] .
A mixture of 2-amino-5-iodo-3-methyl-benzoic acid (12, 15 g,
4 mmol) in 90 ml of methanol was treated dropwise with 81 ml
5
4.1.13. 6-Methoxy-8-methyl-1H-quinazolin-4-one (17)
of a 2 M solution of (trimethylsilyl)diazomethane in hexane.
During the addition the temperature was not allowed to exceed
Formamidine acetate (6.2 g, 60 mmol) was added to a solution
of methyl 2-amino-5-methoxy-3-methyl benzoate (16, 2.9 g,
14 mmol) in 100 ml of 2-methoxyethanol. The reaction mixture
was heated for 16 h to reflux, then cooled down to room
temperature and evaporated under reduced pressure. The
remaining solid was taken up in a saturated aqueous sodium bicar-
bonate solution, filtered, washed with water and dried to deliver
4
0 °C. The reaction mixture was stirred 2 h at room temperature,
then the solvent was removed under reduced pressure to deliver
methyl 2-amino-5-iodo-3-methyl-benzoate (13, 15.6 g, 54 mmol,
9
9%), which was pure enough to be directly used in the next
1
6
step. H NMR (acetone-d ): d = 2.03 (s, 3H), 3.69 (s, 3H), 6.32
Please cite this article in press as: Beaudegnies, R.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.08.009

R. Beaudegnies et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
7
6
8
7
-methoxy-8-methyl-1H-quinazolin-4-one (17, 2.2 g, 12 mmol,
6%). H NMR (DMSO): d = 2.51 (s, 3H), 3.84 (s, 3H), 7.29 (d, 1H),
triturated with dichloromethane, the resulting mixture concen-
trated under reduced pressure to deliver 2-(8-methylquinazolin-
1
.35 (d, 1H), 8.00 (s, 1H), 12.17 (br s, 1H). LC–MS: Rt = 1.20 min;
6-yl)oxy-2-methylsulfanyl-acetic acid (21, 0.9 g, 3.4 mmol, 79%).
+
1
MS: m/z = 191 [M+1] .
6
H NMR (DMSO-d ): d = 2.12 (s, 3H), 2.67 (s, 3H), 5.44 (s, 1H),
7
.27 (d, 1H), 7.57 (d, 1H), 9.13 (s, 1H), 9.35 (s, 1H), 9.36 (s, 1H).
+
4
.1.14. 4-Chloro-6-methoxy-8-methylquinazoline (18)
LC–MS: Rt = 1.35 min; MS: m/z = 265 [M+1] .
Phosphorus oxychloride (15.3 g, 0.1 mol) was added to a mix-
ture of 6-methoxy-8-methyl-1H-quinazolin-4-one (17, 2.2 g,
2 mmol) and N,N-dimethylaniline (2.9 g, 24 mmol) at room tem-
4.1.18. N-(1,1-Dimethylbut-2-ynyl)-2-(8-methylquinazolin-6-yl)-
oxy-2-methylsulfanyl-acetamide (22)
1
perature. The reaction mixture was stirred for 2 h at 70 °C, then
cooled down to room temperature and evaporated in vacuo. The
remainder was taken up in ethyl acetate and washed with satu-
rated aqueous sodium bicarbonate solution. The organic layer
was dried over magnesium sulfate and concentrated under
reduced pressure to deliver 4-chloro-6-methoxy-8-methylquina-
zoline (18, 2.5 g, 12 mmol, 99%), which was pure enough to be
1,1-Dimethylbut-2-yn-1-amine
(51 mg,
0.38 mmol)
N-ethyldiisiopropylamine (0.12 g, 0.95 mmol), catalytic amounts
of 4-dimethylaminopyridine and then benzotriazol-1-yloxy)tris
(dimethylamino) phosphonium hexafluorophosphate (BOP,
Castro’s reagent, 0.19 g, 0.43 mmol) were added consecutively to
a solution of 2-(8-methylquinazolin-6-yl)oxy-2-methylsulfanyl-
acetic acid (21, 0.1 g, 0.38 mmol) in 7 ml of N,N-dimethylfor-
mamide. The reaction mixture was stirred for 3 h at room
temperature, then poured on brine and extracted with ethyl acet-
ate. The organic layer was washed with water and brine, dried over
magnesium sulfate and evaporated under reduced pressure, the
residue was purified by chromatography on silica gel, using ethyl
acetate and cyclohexane as eluents to deliver N-(1,1-dimethyl-
but-2-ynyl)-2-(8-methylquinazolin-6-yl)oxy-2-methylsulfanyl-
directly used in the next step. 1H NMR (CDCl
.97 (s, 3H), 7.28 (d, 1H), 7.43 (d, 1H), 8.93 (s, 1H). LC–MS:
3
): d = 2.72 (s, 3H),
3
+
Rt = 1.68 min; MS: m/z = 209 [M+1] .
4
.1.15. 8-Methylquinazolin-6-ol (19)
0% Palladium on carbon (0.4 g, 0.4 mmol was added to a mix-
ture of 4-chloro-6-methoxy-8-methylquinazoline (18, 2.1 g,
0 mmol) and triethylamine (1.4 g, 14 mmol) in 25 ml of ethyl
1
1
1
acetamide (22, 0.1 g, 0.3 mmol, 79%). Mp 145–147 °C. H NMR
acetate. The reaction mixture was stirred under a hydrogen atmo-
sphere for 16 h at room temperature and then filtered through
Celite. The filtrate was washed with aqueous saturated sodium
bicarbonate solution, water and brine, dried over magnesium sul-
fate and concentrated under reduced pressure to deliver 1.2 g of
3
(CDCl ): d = 1.70 (s, 6H), 1.83 (s, 3H), 2.21 (s, 3H), 2.80 (s, 3H),
5.64 (s, 1H), 6.68 (br s, 1H), 7.17 (d, 1H), 7.52 (d, 1H), 9.29 (s,
+
2H). LC–MS: Rt = 1.64 min; MS: m/z = 344 [M+1] .
4.1.19. 4-Chloro-6-methoxy-1,3-benzothiazol-2-amine (24)
Potassium thiocyanate (14.3 g, 0.15 mol) was added to a solu-
tion of 2-chloro-4-methoxyaniline (23, 5.8 g, 37 mmol) in 60 ml
of acetic acid. After stirring this mixture for 10 min at room tem-
perature, a solution of bromine (5.9 g, 37 mmol) in 60 ml of acetic
acid was added dropwise. The reaction mixture was stirred for 16 h
at room temperature, then neutralized with aqueous ammonium
hydroxide solution and extracted with ethyl acetate. The organic
layer was washed with brine, dried over magnesium sulfate and
evaporated under reduced pressure to deliver 4-chloro-6-meth-
oxy-1,3-benzothiazol-2-amine (24, 2.8 g, 13 mmol, 36%). 1H NMR
6
-methoxy-8-methylquinazoline, which was dissolved in 60 ml
of dichloromethane. Boron tribromide (9.1 g, 36 mmol) was added
and then the reaction mixture was irradiated under microwave
conditions for 1 h at 100 °C. Subsequently, the reaction mixture
was cooled, diluted with ethyl acetate and neutralized with satu-
rated aqueous sodium bicarbonate solution. The organic layer
was washed with brine, dried over magnesium sulfate and concen-
trated under reduced pressure to deliver 8-methylquinazolin-6-ol
(
19, 1.1 g, 7.0 mmol, 70%), which was pure enough to be directly
1
used in the next step. H NMR (CDCl
3
): d = 2.69 (s, 3H), 7.16 (d,
1
H), 7.47 (d, 1H), 9.14 (s, 1H), 9.40 (s, 1H), 10.32 (br s, 1H).
6
(DMSO-d ): d = 3.78 (s, 3H), 6.96 (d, 1H), 7.35 (d, 1H), 7.82 (br s,
2H). LC–MS: Rt = 1.36 min; MS: m/z = 215 [M+1] .
+
+
LC–MS: Rt = 0.98 min; MS: m/z = 161 [M+1] .
4
.1.16. Methyl 2-(8-methylquinazolin-6-yl)oxy-2-methylsulfanyl-
acetate (20)
Methyl 2-chloro-2-(methylsulfanyl)acetate (1.7 g, 11 mmol)
was added to a suspension of 8-methylquinazolin-6-ol (19, 1.1 g,
4.1.20. 4-Chloro-6-methoxy-1,3-benzothiazole (25)
A solution of sodium nitrite (5.2 g, 75 mmol) in 20 ml of water
was added dropwise at ꢁ10 °C to a solution of 4-chloro-6-meth-
oxy-1,3-benzothiazol-2-amine (24, 2.7 g, 12 mmol) in 100 ml of
85% phosphorous acid under strong stirring. The mixture was stir-
red for 1 h at room temperature, then 38 ml of 50% hydrophospho-
rous acid were added dropwise at this temperature. The reaction
mixture was stirred for 1 h at room temperature, then an aqueous
sodium carbonate solution was added and the mixture was
extracted with dichloromethane. The organic layer was washed
with water, dried over magnesium sulfate and evaporated under
reduced pressure, the residue was purified by chromatography
on silica gel, using ethyl acetate and hexane as eluents to deliver
7
2
.0 mmol) and milled potassium carbonate (3.8 g, 28 mmol) in
5 ml of N,N-dimethylformamide. The reaction mixture was stirred
for 4 h at room temperature and then filtered. The filtrate was
diluted with ethyl acetate. The organic layer was washed with
water and brine, dried over magnesium sulfate and evaporated
under reduced pressure. The residue was purified by chromatogra-
phy on silica gel, using ethyl acetate and hexane as eluents to
deliver methyl 2-(8-methylquinazolin-6-yl)oxy-2-methylsulfanyl-
acetate (20, 1.2 g, 4.3 mmol, 62%). 1H NMR (CDCl
): d = 2.25 (s,
H), 2.77 (s, 3H), 3.88 (s, 3H), 5.74 (s, 1H), 7.11 (d, 1H), 7.56 (d,
H), 9.27 (s, 2H). LC–MS: Rt = 1.50 min; MS: m/z = 279 [M+1] .
3
3
1
4-chloro-6-methoxy-1,3-benzothiazole (25, 1.2 g, 6.0 mmol, 48%).
+
1
3
H NMR (CDCl ): d = 3.90 (s, 3H), 7.21 (d, 1H), 7.33 (d, 1H), 8.90
+
(
s, 1H). LC–MS: Rt = 1.56 min; MS: m/z = 200 [M+1] .
4
.1.17. 2-(8-Methylquinazolin-6-yl)oxy-2-methylsulfanyl-acetic
acid (21)
4.1.21. 4-Chloro-1,3-benzothiazol-6-ol (26)
A
suspension of methyl 2-(8-methylquinazolin-6-yl)oxy-2-
15 ml of a 1 M solution of boron tribromide in dichloromethane
were slowly added at ꢁ30 °C to a solution of 4-chloro-6-methoxy-
1,3-benzothiazole (25, 1.0 g, 5.0 mmol) in 50 ml of dichloro-
methane. After the end of the addition the reaction mixture was
allowed to reach room temperature and was stirred for 16 h at this
temperature. 50 ml of methanol were slowly added and the
methylsulfanyl-acetate (20, 1.2 g, 4.3 mmol) in 30 ml of ethanol
was treated with 3.1 ml of a 2 N solution of sodium hydroxide in
water. The reaction mixture was stirred for 1 h at room tempera-
ture, then cooled down to 0 °C, acidified with 2 N hydrochloric acid
until pH 7 was reached and evaporated. The remainder was
Please cite this article in press as: Beaudegnies, R.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.08.009

8
R. Beaudegnies et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
resulting mixture was stirred for further 16 h at room temperature.
The mixture was concentrated in vacuo and the remainder was
taken up in ethyl acetate. The organic layer was washed with water
and brine, dried over magnesium sulfate and evaporated under
with a sporangia suspension containing 50,000 spores/mL. The
inoculated test plants were subsequently incubated in a growth
chamber at 18 °C with 14 h light/day and 100% rh. The percentage
leaf area covered by disease was assessed when an appropriate
level of disease appeared on untreated check plants (5–7 days after
application).
reduced pressure to deliver 4-chloro-1,3-benzothiazol-6-ol (26,
1
0
.9 g, 4.7 mmol, 94%). H NMR (DMSO): d = 7.09 (d, 1H), 7.43 (d,
1
H), 9.18 (s, 1H), 10.21 (br s, 1H). LC–MS: Rt = 1.19 min; MS:
+
m/z = 186 [M+1] .
4.2.2. Plasmopara viticola/grape (activity against downy mildew
on grapevine)
4
.1.22. Ethyl 2-[(4-chloro-1,3-benzothiazol-6-yl)oxy]-2-methyl-
Three-week old grape seedlings cv. Gutedel were sprayed in a
spray chamber with the formulated test compounds diluted in
water. One day after application, the test plants were spray-inocu-
lated on the lower leaf-surface with a sporangia suspension con-
taining 70,000 spores/mL. The inoculated test plants were then
incubated at 22 °C and 100% rh in a greenhouse and the percentage
leaf area covered by disease was assessed when an appropriate
level of disease appeared on untreated check plants (6–8 days after
application).
sulfanyl-acetate (27)
Milled potassium carbonate (1.5 g, 11 mmol) and ethyl
2
-chloro-2-(methylsulfanyl)acetate (1.25 g, 5.9 mmol) were added
consecutively to a suspension of 4-chloro-1,3-benzothiazol-6-ol
26, 0.9 g, 4.7 mmol) in 25 ml of N,N-dimethylformamide. The
(
reaction mixture was stirred for 2 h at 60 °C, then poured on water
and extracted with ethyl acetate. The organic layer was washed
with brine, dried over magnesium sulfate and evaporated under
reduced pressure. The residue was purified by chromatography
on silica gel, using ethyl acetate and cyclohexane as eluents to deli-
4.2.3. Pythium ultimum/cotton (activity against damping-off on
cotton)
ver ethyl 2-[(4-chloro-1,3-benzothiazol-6-yl)oxy]-2-methylsul-
fanyl-acetate (27, 1.2 g, 3.8 mmol, 81%). H NMR (CDCl
1
3
): d = 1.35
A defined amount of mycelium of P. ultimum was mixed with
water. The formulated test compounds were added to the myce-
lium suspension. The mixture was applied into a pouch equipped
with a custom-built folded filter paper. After the application four
cotton seeds cv. Millenium were sown into the upper fold of the fil-
ter paper. The prepared pouches were then incubated for 6 days at
17 °C with 14 h light/day and 100% rh followed by 4 days at 22 °C
and 80% rh with a photo period of 14 h. The evaluation was made
by visual assessment of the emergence and the level of disease on
roots and shoot.
(
(
t, 3H), 2.24 (s, 3H), 4.33 (q, 2H), 5.62 (s, 1H), 7.33 (d, 1H), 7.48
d, 1H), 8.96 (s, 1H). LC–MS: Rt = 1.78 min; MS: m/z = 318 [M+1] .
+
4
.1.23. 2-[(4-Chloro-1,3-benzothiazol-6-yl)oxy]-2-methylsulfanyl-
acetic acid (28)
A suspension of ethyl 2-[(4-chloro-1,3-benzothiazol-6-yl)oxy]-
2
-methylsulfanyl-acetate (27, 1.2 g, 3.8 mmol) in 40 ml of tetrahy-
drofurane was slowly treated at 0 °C with 10 ml of a 0.5 N solution
of sodium hydroxide in water. The reaction mixture was stirred for
1
h between 0 and 10 °C, then warmed to room temperature,
poured on ethyl acetate and acidified with 1 N hydrochloric acid
until pH 3 was reached. The mixture was washed with brine, dried
over magnesium sulfate and evaporated under reduced pressure to
4.2.4. Pythium ultimum (activity in liquid culture)
A Mycelia fragments and oospores of a newly grown liquid cul-
ture of the fungus are directly mixed into nutrient broth (PDB
potato dextrose broth). After placing a (DMSO) solution of test
compound into a microtiter plate (96-well format), the nutrient
broth containing the fungal mycelia/spore mixture is added. The
test plates are incubated at 24 °C and the inhibition of growth is
determined photometrically 2–3 days after application.
deliver 2-[(4-chloro-1,3-benzothiazol-6-yl)oxy]-2-methylsulfanyl-
1
acetic acid (28, 1.0 g, 3.5 mmol, 91%).
6
H NMR (DMSO-d ):
d = 2.13 (s, 3H), 6.07 (s, 1H), 7.45 (d, 1H), 7.86 (d, 1H), 9.33 (s,
+
1
H). LC–MS: Rt = 1.60 min; MS: m/z = 290 [M+1] .
4
.1.24. 2-[(4-Chloro-1,3-benzothiazol-6-yl)oxy]-N-(1,1-dimethyl-
but-2-ynyl)-2-methylsulfanyl-acetamide (3)
-Hydroxy-7-azabenzotriazole (66 mg, 0.5 mmol), 2-(1-H-ben-
zotriazol-1-yl)-1,1,3,3,-tetramethyluronium tetrafluoroborate
TBTU, 0.15 g, 0.5 mmol) and 1,1-dimethylbut-2-yn-1-amine
65 mg, 0.5 mmol) were added consecutively to a solution of 2-
(4-chloro-1,3-benzothiazol-6-yl)oxy]-2-methylsulfanyl-acetic acid
28, 0.13 g, 0.5 mmol) and triethylamine (0.14 g, 1.4 mmol) in
Acknowledgement
1
The authors gratefully acknowledge the excellent synthetic
contribution of Myriam Baalouch, Thomas Grether, Nikola
Kokosar, Jerome Sachet, Grit Schade and Thomas Steffen.
(
(
[
(
References and notes
8
ml of acetonitrile. The reaction mixture was stirred for 16 h at
room temperature, then poured on saturated aqueous ammonium
chloride solution and extracted with ethyl acetate. The organic
layer was washed with brine, dried over magnesium sulfate and
evaporated under reduced pressure, the residue was purified by
chromatography on silica gel, using ethyl acetate and cyclohexane
1
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d = 1.71 (s, 6H), 1.84 (s, 3H), 2.20 (s, 3H), 5.53 (s, 1H), 6.69 (br s,
H), 7.32 (d, 1H), 7.50 (d, 1H), 8.99 (s, 1H). LC–MS: Rt = 1.77 min;
3
1
3
.
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+
MS: m/z = 369 [M+1] .
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