synthesis and structure–activity study of fungicidal anilinopyrimidines leading to mepanipyrim...

Pest Management Science Pest Manag Sci 60:399–407 (online: 2003)DOI: 10.1002/ps.828

Synthesis and structure–activity studyof fungicidal anilinopyrimidines leading tomepanipyrim (KIF-3535) as an anti-BotrytisagentToshihiro Nagata,1∗ Katsumi Masuda,2 Shinichiro Maeno2 and Ichiro Miura2

1K-I Chemical Research Institute Co Ltd, Fukude-cho, Iwata-gun, Shizuoka 437-1213, Japan2Kumiai Chemical Industry Co Ltd, Life Science Research Institute, Kikugawa, Ogasa-gun, Shizuoka 439-0031, Japan

Abstract: A series of 2-anilinopyrimidines was prepared and their fungicidal activities against Botrytiscinerea Pers were examined. The activity fell sharply with any substitution on the anilinobenzene ring.Substitutions at the 5-position of the pyrimidine ring greatly reduced the activity. Substituents such aschloro, methoxy, methylamino, methyl or 1-propynyl were well tolerated at the 4- and 6-positions ofthe pyrimidine ring. Among these substituents, the combination of methyl and 1-propynyl groups wasthe most favourable. 2-Anilino-4-methyl-6-(1-propynyl)pyrimidine (KIF-3535), which showed excellentactivity and no significant phytotoxicity, was finally selected for development and has been given thecommon name mepanipyrim. 2003 Society of Chemical Industry

Keywords: fungicide; Botrytis cinerea; grey mould; anilinopyrimidine; mepanipyrim; KIF-3535

1 INTRODUCTIONGrey mould induced by Botrytis cinerea Pers is animportant disease, causing a considerable yield reduc-tion in vegetables and vine. Benzimidazoles and dicar-boximides have been mainly used for controlling Bcinerea in recent years, but the development of strainsresistant to these compounds has seriously obstructedthis. Therefore, new fungicides with a different modeof action were needed to improve the control of theinfection.

In a research project to develop ‘pyrimidinyl-carboxy herbicides’ as a new type of ALS inhibitor,1,2

(Fig 1), we attempted a reaction of the sodium saltof the salicylaldimine 1 and the sulfonylpyrimidine2 to give the phenylimino compound 3. However,the reaction did not give the desired product 3 but,unexpectedly, an anilinopyrimidine 4 and an aldehyde5 were obtained (Fig 2). The anilinopyrimidine 4exhibited potent fungicidal activity against B cinerea.

This paper describes optimization of compound 4as the lead to develop mepanipyrim 6 by varying thesubstituents R, Rn (n = 1 ∼ 3), W, X, Y and Z ingeneral structures of 7 and 8 shown in Fig 3.

2 MATERIALS AND METHODS2.1 GeneralMelting points were uncorrected. IR spectra wererecorded in potassium bromide on a Hitachi 260-10

spectrometer. Refractive indexes were measured withan Atago–Abbe 3T refractometer. 1H NMR spectrawere obtained in deuterochloroform (unless otherwisestated) on either a JEOL JMN-PMX-60Si or a JEOLJMN-GSX-400 instrument; chemical shifts were givenin ppm (δ) from an internal tetramethylsilane standard,coupling constants (J) were given in Hz.

2.2 SynthesisThe test compounds were synthesized by variousmethods as shown in Fig 4. Among anilinopyrim-idines, 4, 6, 32, 39 44–52, 563 –59, 65,4 66,5 71–73,6

78–82 and 84–88 were prepared by hydrolysis of N-formylanilinopyrimidines 11 obtained by coupling ofcorresponding formanilides 97 with corresponding 2-methylsulfonylpyrimidines 10 (method A). Syntheticroutes for 2-methylsulfonylpyrimidines 10 are summa-rized in Fig 5. Compounds 20,8 25,9 and 2610 wereprepared by reported methods.

Compounds 67,11,12 68, 69,13,14 and 70,15,16 and74 were obtained by condensation of phenylguani-dine nitrate 1217 and diketones 13 (method B, Pinnerreaction).18 Heating alkylamines 14, which are morenucleophilic than the corresponding anilines, with the2-methylsulfonylpyrimidine 10a in toluene producedalkylaminopyrimidines 33 and 34. (method C).19

Treatment of aminopyridines with n-butyl lithium fol-lowed by reaction with the 2-methylsulfonylpyrimidine

∗ Correspondence to: Toshihiro Nagata, K-I Chemical Research Institute Co, Ltd, Fukude-cho, Iwata-gun, Shizuoka 437-1213, JapanE-mail: [email protected](Received 10 February 2003; revised version received 27 August 2003; accepted 25 September 2003)Published online 2 December 2003

2003 Society of Chemical Industry. Pest Manag Sci 1526–498X/2003/$30.00 399

T Nagata et al

COOCH3

ON

NCl

OCH3

COONa

SN

NOCH3

OCH3

ClCOOCH3

ON

NOCH3

OCH3

NOCH3

COONa

ON

NOCH3

OCH3

ON

N

H3CO

H3CO

Herbicidal lead compound Pyrithiobac-sodium Pyriminobac-methyl

Bispyribac-sodium

Figure 1. ‘Pyrimidinyl-carboxy’ herbicides.

CH

OH

N

N

NCl

OCH3

BnSO2

NaOCH3

NHN

NCl

OCH3

NHN

NCH3

C C CH3

N

NCl

OCH3

CH

O

N

N

N Cl

OCH3

CHO

O

4 56 Mepanipyrim

+

+

1 2 3Bn = benzyl

Optimization

Figure 2. Discovery of a fungicidal lead and development of mepanipyrim.

R YW

ZN

R1

R3

NHN

NR1

R3

XR2

7 8

Figure 3. Structures of compounds synthesized.

10a afforded pyridylaminopyrimidines 29–31 (methodD). These pyridylamino compounds were not obtain-able by the methods A and C. Phenol and thiophenol16 reacted with the 2-methylsulfonylpyrimidine 10ato give phenoxypyrimidine 35 and phenylthiopyrim-idine 36, respectively (method E).20 The triazolecounterpart 53 and the position isomer 5421 of com-pound 4 were prepared by reaction of 17 (X = Cland SO2CH3, respectively) and sodium methox-ide (method F1).22–24 With alkoxy, alkylamino, andmethylthio substituents at the 4-and/or 6-position(s)of the pyrimidine ring, compounds 55, 61–64, and83, were prepared by nucleophilic displacement of theappropriate pyrimidinylchlorides (method F1). Thechloro compound 59 was fluorinated to compound60 by using spray-dried potassium fluoride (methodF2). Cyanation of the chloro compound 57 withpotassium cyanide gave the corresponding cyanide75 (method F3).25 Alkylation and acylation of theanilinopyrimidine 4 with sodium hydride afforded N-substituted anilinopyrimidines 40–43 (method F4).The phenylthio compound 36 was oxidized to thecorresponding sulfoxide 37 and sulfone 38 with m-chloroperbenzoic acid (method F5). Condensation of

methoxyamine with the aldehyde 18 gave the oximeether 76 (method F6). The Wittig reaction withthe aldehyde 18 gave the 1-propenylpyrimidine 77(method F7).

2.2.1 General procedure for method A: synthesis of2-(N-formylanilino)-4-methyl-6-(1-propynyl)pyrimidine11 and 2-anilino-4-methyl-6-(1-propynyl)pyrimidine 6To a suspension of sodium hydride (60% in mineraloil, 42 g, 1.05 mol, pre-washed with hexane) intoluene (or tetrahydrofuran; THF) (2 litres) was addedformanilide (138.6 g, 1.15 mol), and the mixture washeated to 50 ◦C for 30 min. Methylsulfonylpyrimidine10e (200.5 g, 0.955 mol) was then added to themixture. After stirring at room temperature for15 h, the mixture was poured into ice–water, andextracted with ethyl acetate. The extract was driedand evaporated under vacuum. The solid residue waswashed with isopropyl ether to give 11 (179 g, 75%).

To a solution of 11 (179 g, 0.713 mol) obtained fromabove reaction in ethanol + THF (2 + 1 by volume,1 litre) was added aqueous sodium hydroxide solution(3 M; 250 ml). The mixture was stirred at roomtemperature for 5 h, poured into water and extractedwith ethyl acetate. The organic layer was washed withbrine, dried and evaporated under vacuum. The crudeproduct was recrystallized from hexane + isopropylether (1 + 1 by volume) to give 6 (136 g, 86%): mp124–126 ◦C; 1H NMR: δ 2.05 (s, 3H), 2.39 (s, 3H),6.59 (s, 1H), 6.80–7.70 (m, 6H); IR: 3260, 2230,1600, 1570, 1540, 1490, 1435, 1340, 1245, 750 cm−1.

400 Pest Manag Sci 60:399–407 (online: 2003)

Mepanipyrim and other anilinopyrimidine activity against Botrytis cinerea

AX

NHCHON

N R1

R3

CH3SO2 R2

C

D

B

N

R NH2

NH2

NH

NH2

NH

HNO3

N

N Cl

OCH3

CH3SO2

N

N Cl

OCH3

CH3SO2

R1

R3

O

O

XNH

N

N R1

R3

R2

E AHN

N Cl

OCH3

CH3SO2

NHW

ZN R1

X

F1 NHW

ZN R1

R3

X

N

NHN

N R1

R3

NN

N R1

R3

R2

CHO

NHN

N Cl

OCH3

R

AN

N Cl

OCH3

N

N Cl

OCH3

NH

+

+

+

A = O, S

+

+

9 10

12 13

14 R = Alkyl10a

15 10a

16 10a

17

11, 39

a

b

c

d

e

f

g

X = Cl, SO2CH3

.

67-70, 74

33, 34

29-31

35, 36

53-55, 61-64, 83

F2

F3

F4

NHN

N Cl

Cl

NHN

N CH3

Cl

NHN

N Cl

OCH3

SN

N Cl

OCH3

NHN

N CH3

CHO

NHN

N CH3

CHO

F5

F6

F7

NHN

N Cl

F

NHN

N CH3

CN

SN

N Cl

OCH3(O)n

NN

N Cl

OCH3R4

NHN

N CH3

CH CHCH3

NHN

N CH3

CH NOCH3

4

18

18

h

i

j

k

l

m

6059

57 75

40-43

3637, 38

76

77

Figure 4. Synthetic methods of test compounds. (a) NaH, THF; (b) NaOH, EtOH–H2O; (c) Na2CO3, EtOH, reflux; (d) toluene, reflux; (e) n-BuLi, THF,−60 ◦C ∼ room temp; (f) NaH, THF, room temp; (g) Nu, solv; (h) KF, sulfolane, 150 ◦C; (i) KCN, DMSO, 100 ◦C; (j) (1) NaH, DMF, room temp, (2) R4X,room temp; (k) mCPBA, CH2CI2, room temp; (I) H2NOCH3, NaOAc, EtOH, room temp; (m) Ph3PCH3Br, n-BuLi, THF, 0 ◦C ∼ room temp.

2.2.2 General procedure for method D: synthesis of 4-chloro-6-methoxy-2-(pyridine-2-yl)aminopyrimidine 29To a solution of 2-aminopyridine 15 (1.5 g, 16 mmol)in THF (80 ml) was added n-butyl lithium (11 ml,17.6 mmol, 1.6 M in hexane) at −60 ◦C. The mixturewas allowed to warm to −40 ◦C and stirred for15 min. 10a (3.9 g, 17.6 mmol) was added to themixture at −60 ◦C. The resulting solution wasallowed to warm to room temperature, stirred for

30 min, poured into ice–water, and extracted withethyl acetate. The organic layer was washed withbrine, dried and concentrated. The residue wassubjected to chromatography (hexane + ethyl acetate)to give 29 (1.5 g, 40%): mp 163–166 ◦C; 1H NMR(hexadeuterodimethyl sulfoxide): δ 3.95 (s, 3H), 6.49(s, 1H), 6.90–7.17 (m, 1H), 7.62–7.93 (m, 1H),10.10 (bs, 1H); IR: 2990, 1600, 1560, 1525, 1435,1360, 1285, 1005, 765 cm−1.

Pest Manag Sci 60:399–407 (online: 2003) 401

T Nagata et al

N

N CH3

Cl

CH3SN

N CH3

I

CH3S

N

N NH

Cl

CH3SPh

N

N CH3

CH3S

R

N Cl

Cl

CH3SN

N

N NH

Cl

CH3SO2

Ph

N

N I

I

CH3S

N

N CH3

CH3SO2

R

N

NCH3S

CH3

CH3

N

N Cl

I

CH3S

N

N Cl

OCH3

CH3S

N

N ClCH3S

CH3

N

NCH3SO2

CH3

CH3

N

N Cl

OCH3

CH3SO2

N

N ClCH3SO2

CH3

10a

+

R = TMS, Me, Et, n-Pr

+

20

19

21

22

23

24

10b

10c

25 10d

26 27 28 10 (10e: R = Me)

a

b

c

b

b

b

d

e

b

c d

Figure 5. Synthetic routes for methylsulfonylpyrimidines 10. (a) NaOMe, MeOH; (b) OXONER, MeOH–H2O, room temp; (c) HI, 60 ◦C; afforded amixture of the mono-(21) and di-iodides (22) (ratio of 35:65). (d) HC≡CR, Pd(Ph3)2 CI2, Cul, Et3N–THF; gave a mixture of the mono-(23) anddi-propynyl (24) compounds in 18 and 43% yields, respectively, starting from 19. (e) PhNH2, HCI, acetone–H2O, reflux.

2.2.3 Procedure for method F2: synthesis of2-anilino-4-chloro-6-fluoropyrimidine 60A mixture of 59 (4.1 g, 17.1 mmol) and spray-driedpotasium fluoride (1.2 g, 20.7 mmol) in sulfolane(30 ml) was stirred at 150 ◦C for 2 h. The mixturewas then poured into water and extracted with diethylether. The organic layer was washed with brine,dried and evaporated under vacuum. The residue waschromatographed (hexane + diethyl ether, 9 + 1 byvolume) to give 60 (2.1 g) that was 69% pure whenexamined by GC. Recrystallization from hexane gave1.5 g (39%) of 60 (72% pure by GC) (containing 9%of 59 and 19% of 2-anilino-4,6-difluoropyrimidine):mp 97–98 ◦C; 1H NMR: δ 6.26 (d, J = 2.1 Hz, 1H),6.90–7.82 (m, 6H). IR: 3290, 1605, 1580, 1530,1445, 1380, 915, 795, 750 cm−1.

2.2.4 General procedure for method F4: synthesis of2-(N-methylanilino)-4-chloro-6-methoxypyrimidine 40To a suspension of sodium hydride (60% in mineraloil, 0.50 g, 13 mmol, pre-washed with hexane) inN, N-dimethylformamide (DMF; 50 ml), 4 (3.0 g,13 mmol) was added, and the mixture was stirredat room temperature for 30 min. Methyl iodide (2.8 g,20 mmol) was then added dropwise. The resultingmixture was stirred at room temperature for 4 h,poured into ice–water and extracted with ethyl acetate.The organic layer was washed with water and brine,dried, and concentrated under vacuum. The residuewas chromatographed (hexane + ethyl acetate) to give40 (1.8 g, 56%): nd20 1.5992; 1H NMR: δ 3.54 (s,3H), 3.72 (s, 3H), 6.10 (s, 1H), 7.16–7.48 (m, 5H);IR: 2950, 1600, 1575, 1540, 1500, 1400, 1335, 1250,695 cm−1.

2.2.5 Procedure for method F6: synthesis of2-anilino-4-methoxyiminomethyl-6-methylpyrimidine 76A mixture of 18 (2.5 g, 11.7 mmol), methoxyaminehydrochloride (1.0 g, 11.7 mmol), and sodium acetate(2.5 g, 23.4 mmol) in ethanol (100 ml) was stirredat room temperature for 1 h. Upon completion(TLC), the reaction mixture was poured into waterand extracted with ethyl acetate. The organic layerwas washed with water and brine, dried, andconcentrated under vacuum. The residue was purifiedby chromatography (hexane + ethyl acetate) to give76 (1.8 g, 64%): mp 76–77 ◦C; 1H NMR: δ 2.40(s, 3H), 3.98 (s, 3H), 6.96 (s, 1H), 7.00–7.70 (m,6H), 7.86 (s, 1H); IR: 3390, 1580, 1525, 1430, 1340,1025 cm−1.

2.2.6 Procedure for method F7: synthesis of2-anilino-4-methyl-6-(1-propenyl)pyrimidine 77To a suspension of methyl triphenylphosphoniumbromide (7.6 g, 18 mmol) in THF (50 ml) was addedn-butyl lithium (12 ml, 19.2 mmol, 1.6 M in hexane)at 0 ◦C. After stirring at room temperature for 1 h,a solution of 18 (2.6 g, 12 mmol) in THF (10 ml)was added dropwise at 0 ◦C. The resulting mixturewas stirred at room temperature for 1 h, pouredinto ice–water, and extracted with ethyl acetate. Theorganic layer was washed with water and brine, dried,and concentrated under vacuum. The residue waspurified by chromatography (hexane + ethyl acetate)to give 77 (0.8 g, 30%): nd20 1.6408; 1H NMR: δ 1.92(dd, J = 6.6, 1.2 Hz, 3H), 2.36 (s, 3H), 6.06–6.40(m, 2H), 6.44 (s, 1H), 6.88–9.76 (m, 6H); IR: 3260,3030, 1595, 1575, 1530, 1495, 1435, 1345, 1245,750 cm−1.



2.2.7 General procedure for iodination (Fig 5, procedurec): synthesis of 4-iodo-6-methyl-2-methylthiopyrimidineTo hydroiodic acid (1 kg, 57%) was added liquid 26(200 g, 1.15 mol, melted by heat) with mechanicallystirring. The resulting suspension was stirred at 50 ◦Cfor 24 h, filtered and washed with water. The filtercake was neutralized to pH 8 with aqueous sodiumhydrogen carbonate and extracted with ethyl acetate.The organic layer was washed with aqueous sodiumthiosulfate and water, dried and concentrated underreduced pressure. The residual solid was rinsed withhexane to give 27 (256 g, 84%) as a colourless solid;mp 103–104 ◦C; 1H NMR: δ 2.36 (s, 3H), 2.53 (s,3H), 7.29 (s, 1H); IR: 2925, 1540, 1555, 1510, 1280,1250, 1115, 775 cm−1.

2.2.8 General procedure for palladium cross-coupling(Fig 5, procedure d): synthesis of4-methyl-2-methylthio-6-(1-propynyl)pyrimidine 2826

Propyne (50 g, 1.25 mol) was bubbled into a mixtureof 27 (255 g, 0.959 mol), Pd(Ph3P)2Cl2 (1.3 g,1.9 mmol) and copper(I) iodide (0.18 g, 0.96 mmol) intriethylamine (1500 ml) with vigorous stirring at roomtemperature over 5 h. The reaction exothermed to35–40 ◦C. Stirring was continued at room temperaturefor 5 h. After filtration of the reaction mixture, thefiltrate was evaporated. The residue was partitionedbetween toluene and water. The organic layer waswashed with water, dried, and concentrated at reducedpressure. The residual solid was rinsed with hexaneto give 28 (158 g, 93%) as a light-yellow solid; mp74–75 ◦C; 1H NMR: δ 2.08 (s, 3H), 2.38 (s, 3H),2.50 (s, 3H), 6.76 (s, 1H); IR: 2980, 2230, 1555,1505, 1260, 840, 805 cm−1.

2.2.9 General procedure for the oxidation of2-methylthiopyrimidines (Fig 5 procedure b): synthesis of4-methyl-2-methylsulfonyl-6-(1-propynyl)pyrimidine 10eTo a solution of 28 (R = Me) (158 g, 0.889 mol)in methanol + water (1600 ml + 200 ml) was addedOxone (820 g, 1.33 mol) below 35 ◦C. Water(1400 ml) was then added to the mixture below 35 ◦C.The resulting mixture was stirred at room temperaturefor 5 h and extracted with chloroform (2 × 1000 ml).The combined organic layers were dried and concen-trated at reduced pressure. The residue was rinsedwith isopropyl ether to give 10e (172 g, 92%) as acolourless solid, mp 190–192 ◦C; 1H NMR: δ 2.21(s, 3H), 2.61 (s, 3H), 3.31 (s, 3H), 7.36 (s, 1H); IR:3000, 2920, 2220, 1570, 1495, 1440, 1300, 1130,750 cm−1.

2.3 Biological assay2.3.1 Plant materialsCucumber (Cucumis sativus L cv Sagami-hanjiro)seedlings were used to assay disease-controllingactivity by foliar application. The seeds were sownin plastic pots containing sterilized soil and grown in aglasshouse. The cucumber seedlings at the cotyledon

stage were used to assay the fungicidal activity oncucumber grey mould.

2.3.2 Assay methods for fungicidal activityAqueous suspensions of 100 g kg−1 wettable powdersof each compound at the appropriate concentrationswere sprayed over the cucumber seedlings. After airdrying the seedlings were inoculated by spraying withmycelial homogenate of Botrytis cinerea pre-incubatedin YG liquid medium (yeast extract 3 g litre−1, glucose20 g litre−1) for 5 days on a reciprocal shaker at 20 ◦C.After inoculation, the plants were maintained at20 ◦C for 3 days in a moist chamber. Assessment wasperformed by measuring the percentage of infectedleaf area, and the percentage disease control wascalculated. The fungicidal activity was expressed asan index of 4, 3, 2, 1 and 0, corresponding to 100,90–99, 75–89, 50–74 and 0–49% disease control,respectively. The effective concentration required for50% inhibition of disease control (EC50, mg litre−1)

was calculated by probit analysis.

2.3.3 Crop safety studyCrop safety was evaluated by the pot test in agreenhouse. Eggplant (cv Senryo No 2) and cucumber(cv Sagami-hanjiro) were used as test plants. Eachplant was grown to 3- or 4-leaf stage in unglazedclay pots (12 cm). Aqueous suspensions of 100 g kg−1

wettable powders of each compound at appropriateconcentrations were sprayed over the plants by aspray gun. Two applications were made with a 7-day interval. Crop safety was evaluated by a visualranking scale of 0 (no damage) to 5 (serious damage:almost dead).

3 RESULTS AND DISCUSSIONReplacements of the anilino moiety of compound 4with pyridylamino (29–31), naphthlylamino (32) orcycloalkylamino groups (33, 34) gave compoundswithout activity, except for the cyclopentylaminoderivative 34 (Table 1). The cyclopentane ring issterically similar to the benzene ring of the anilinomoiety. The bridge nitrogen of compound 4 wasreplaced with oxygen, sulfur and substituted nitro-gen structures (Table 2). Compounds 35 (Y = O),36 (Y = S), and 37 (Y = SO) had no activity.Compound 38 (Y = SO2) showed a weak activ-ity. Among compounds substituted at the centralnitrogen (39–43), compounds 39 (formyl) and 43(methoxymethyl) showed a high activity. These com-pounds were assumed to be hydrolyzed to compound4 to exert their fungicidal activity. As shown inTable 3, to retain high activity the benzene ring ofcompound 4 should not be substituted (44–52). Bulkeffects of substituents rather than electronic effectsseem to be unfavourable at any position, becauseboth electron-donating and electron-withdrawing sub-stituents decrease the activity. The pyrimidine moi-ety of compound 4 was modified as shown in


T Nagata et al

Table 4. The triazine 53 and the isomeric 4-anilinopyrimidine 54 showed only weak activity.The above structure-activity data indicated that thecore structure for potent fungicidal activity is 2-(unsubstituted anilino)pyrimidine.

The effects of substitutions of the 4- to 6-positionsof the pyrimidine ring in the lead structure 4 wasexamined in Table 5. R1 and R2 were kept constantas Cl and H, respectively, and R3 was variedin compounds 55–64. Compounds 57 (R3 = CH3),59 (R3 = Cl), and 61 (R3 = NHCH3) were moreactive than compound 4. Bulky substituents like iso-C3H7O (55), iso-C3H7 (58) and (C2H5)2N (63) atthe 6-position decreased the activity. The 5,6-di-unsubstituted compound 56 (R2 = R3 = H) was lessactive than compound 4. The fluorine substituent

Table 1. SAR studies on 2-aminopyrimidines: the N-substituent of

R NHN

NCl

OCH3

Compound mp (◦C)

Fungicidal activityscorea at concentration

(mg litre−1)

number or nd20 R 500 50

4 101–103 Phenyl 4 429 163–166 2-Pyridyl 0 —b

30 196–199 3-Pyridyl 0 —31 191–194 4-Pyridyl 0 —32 Foam 2-Naphthyl 0 —33 1.5487 cyclo-Hexyl 0 —34 1.5568 cyclo-Pentyl 4 1

a Activity against B cinerea, on a scale 4–0 where 4 = 100, 3 = 99–90,2 = 89–75, 1 = 74–50, 0 = 49–0% control.b Not tested.

Table 2. SAR studies on 2-anilinopyrimidines: the central (nitrogen)

atom/group of

YN

NCl

OCH3

Compound mp (◦C)


(mg litre−1)

number or nd20 Y 500 50

4 101–103 NH 4 435 73–77 O 0 —b

36 1.6208 S 0 —37 101–106 SO 0 —38 98–99 SO2 3 039 118–120 NCHO 4 340 1.5992 NCH3 0 —41 1.5838 NCOCH3 3 242 100–101 NCONMe2 2 —43 1.5773 NCH2OCH3 4 3

a,b See Table 1.

Table 3. SAR Studies on 2-anilinopyrimidines: the phenyl

substituent of

NHN

NCl

X

OCH3

Compound


(mg litre−1)

number mp (◦C) X 500 50

4 101–103 H 4 444 74–75.5 2-Cl 0 045 147–149 3-Cl 0 046 151–152 4-Cl 0 047 42–43 2-CH3 0 048 88–89 3-CH3 0 049 118.5–119.5 4-CH3 0 050 102–104 2-OCH3 0 051 106–107.5 3-OCH3 0 052 101–102.5 4-OCH3 0 0

a See Table 1.

Table 4. SAR studies on 2-anilinoazines

NH Az

Compound

Fungicidal activity scorea atconcentration (mg litre−1)

number mp (◦C) Az 500 50

4 101–103

N

NCl

OCH3

4 4

53 145–147

N

NN

Cl

OCH3

2 —b

54 176–177

NN

Cl

OCH3

1 —

a,b See Table 1.

diminished the activity (60). This seems to bedue to the fact that the fluorinated pyrimidinewas easily hydrolyzed by attack of nucleophiles.The effects of 4- and 6-substituents suggested thatcombinations of moderately sized substituents (egCl, OCH3, NHCH3, CH3) at these two positionswere favourable to activity. When R1 was keptconstant as the methyl group, and R3 was varied(65–70), compound 67 (R1 = R3 = CH3) showedgood activity, as expected. However, all highlyactive compounds, such as 57 (R1, R3 = Cl, CH3),59 (R1 = R3 = Cl), 61 (R1, R3 = Cl, NHCH3), 65(R1, R3 = CH3, OCH3), and 67 (R1 = R3 = CH3)

showed unacceptable phytotoxicity (see Table 7).Other less bulky substituents were examined next.The introduction of a ‘lengthy’ but ‘slim’ 1-propynyl



Table 5. SAR studies on 2-anilinopyrimidines: the pyrimidine substituents of

NHN

NR1

R3

R2

Compound


(mg litre−1)

EC50c

(mg litre−1)

number mp (◦C) or nd20 R1 R2 R3 50 10

4 101–103 Cl H OCH3 4 0 6.155 71–75 Cl H O-iso Pr 1 — —b

56 134–135 Cl H H 2 0 2657 85–89 Cl H CH3 4 2 3.758 68–70 Cl H iso-Pr 2 — —59 116–117 Cl H Cl 4 1 3.560 97–98 Cl H F 0 — —61 113–115 Cl H NHCH3 4 2 4.262 140–141 Cl H NMe2 4 0 963 110–112 Cl H NEt2 0 — —64 114–116 Cl H SCH3 0 — —65 75–76 CH3 H OCH3 4 2 2.766 91–92 CH3 H H 4 0 1667d 96.5–98 CH3 H CH3 4 2 46 124–126 CH3 H C≡CCH3 4 4 1.9

68 1.5972 CH3 H iso-Pr 0 — —69e 68–70 CH3 H cyclo-Pr 4 4 3.470 82–83 CH3 H CF3 0 — —71 71–75 OCH3 H OCH3 0 — —72 90–91 Cl CH3 OCH3 0 — —73 100–102 Cl CH3 CH3 0 — —74 99–100 Cl F CH3 0 — —

a See Table 1.b Not tested or not determined.c EC50 denotes the effective concentration required for 50% inhibition.d Pyrimethanil,12 Lit11 mp 98–99 ◦C.e Cyprodinil,14 Lit13 mp 67–69 ◦C.

group as the R3 substituent gave compound 6, showinghigher activity and less phytotoxicity. Substitutions atthe 5-position were observed to greatly reduce theactivity in compounds 72–74.

Compounds similar to 6 and acetylenic compoundswere synthesized (Table 6). Compounds 75 (R3 =CN), 76 (R3 = CH = NOCH3) and 77 (R3 = CH =CHCH3) were less active than compound 6. Terminalacetylenic derivertives 78, 87 and 88 (R1 and/or R3 =ethynyl) were also less active. Longer substituents ledless active compounds 79, 80, 85 and 86. The data ofTable 6 indicated that none of the similar acetylenicderivatives showed more activity than compound 6.

In summary, the 2-anilinopyrimidine skeleton isa requisite structure for a potent fungicidal activ-ity against B cinerea. The benzene ring and the5-position on the pyrimidine ring have to be unsub-stituted. Moderately sized substituents such as Cl,OCH3, NHCH3, CH3 and 1-propynyl were tol-erated at the 4- and 6-positions on the pyrimi-dine ring. Among those substituents, the combina-tion of CH3 and 1-propynyl was most favourable.

2-Anilino-4-methyl-6-(1-propynyl)pyrimidine 6 (KIF-3535), which showed excellent activity and no phy-totoxicity, was selected and has been given thecommon name mepanipyrim.27–29 It should be men-tioned that mepanipyrim is also highly effective againstbenzimidazole- and/or dicarboximide-resistant strainsof B cinerea.

Biochemical studies suggested that mepanipyriminhibits the secretion of cell-wall-degrading enzymes(eg cutinases, pectinases, cellulases) and extracellularproteins of B cinerea.30,31 For pyrimethanil (67), theprimary target was proposed by Fritz et al32 to becystathionine β-lyase in the methionine biosyntheticpathway. The relevant mode of action of theanilinopyrimidine type fungicides is, however, not yetconclusively determined. The inhibition of methioninebiosynthesis could be associated with the inhibition ofthe secretion of hydrolytic enzymes in the mechanismof anti-Botrytis action of this series of compounds.33

ACKNOWLEDGEMENTThe authors gratefully acknowledge Professor ToshioFujita for his invaluable suggestions.


T Nagata et al

Table 6. SAR studies on 2-anilinopyrimidines: the multiple-bond compounds of

NHN

NR1

R3

Compound

Fungicidal activity scorea

at concentration (mg litre−1)EC50

c

number mp (◦C) or nd20 R1 R3 50 10 (mg litre−1)

75 129–130 CH3 C≡N 1 — —b

76 76–77 CH3 CH = NOCH3 3 0 2577 1.6408 CH3 CH = CHCH3 4 0 2078 86–88 CH3 C≡CH 3 0 50

6 124–126 CH3 C≡CCH3 4 4 1.979 120–122 CH3 C≡CC2H5 4 1 680 89–90 CH3 C≡Cn-Pr 0 — —81 165–169 C≡CCH3 H 4 2 4.582 121–124 C≡CCH3 Cl 4 1 5.883 91–92 C≡CCH3 OCH3 1 0 —84 90–91.5 C≡CCH3 C2H5 4 1 8.685 152–155 C≡CCH3 C≡CCH3 0 — —86 120–121 C≡CC2H5 H 1 — —87 51–53 C≡CH C2H5 2 0 8088 90–91 C≡CH C≡CH 0 0 —

a See Table 1.b Not tested or not determined.c EC50 denotes the effective concentration required for 50% inhibition.

Table 7. Crop safety of anilinopyrimidines

NHN

NR1

R3

CompoundPhytotoxicity indexa at concentration (mg litre−1)

number R1 R3 Plants 2000 1000 500 250

4 Cl OCH3 Eggplant 3 1 1 0Cucumber 3 2 1 0

6 CH3 C≡CCH3 Eggplant 0 0 0 —b

Cucumber 0 0 0 —57 Cl CH3 Eggplant 3 2 2 1

Cucumber 3 2 1 059 Cl Cl Cucumber — — 1 —61 Cl NHCH3 Cucumber — — 1 —65 CH3 OCH3 Cucumber — — 1 —

67c CH3 CH3 Eggplant 4 3 1 0Cucumber 4 3 2 1

69d CH3 cyclo-Pr Eggplant 3 2 — —Cucumber 4 3 2 1

a On a scale 0–5 where 0 = no damage, 1, 2, 3, 4, 5 = almost dead.b Not tested.c Pyrimethanil.11,12

d Cyprodinil.13,14

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