Pesticide Synthesis Through Rational Approaches - American

10

Downloaded by UNIV OF CALIFORNIA SAN FRANCISCO on December 5, 2014 | http://pubs.acs.org Publication Date: June 26, 1984 | doi: 10.1021/bk-1984-0255.ch010

Insecticidal and Molluscicidal Activities of Isobutylamides Isolated from Fagara macrophylla and Their Synthetic Analogs ISAO KUBO, JAMES A. KLOCKE, and TAKESHI MATSUMOTO Division of Entomology and Parasitology, College of Natural Resources, University of California, Berkeley, CA 94720 TADAO KAMIKAWA Department of Chemistry, Faculty of Science and Technology, Kinki University, Kowakae, Higashi-osaka-shi, Osaka 577, Japan Five isobutylamides were isolated as insect growth inhibitors and toxicants from Fagara macrophylla and identified from their spectroscopic and chemical data. Synthesis and bioassay of the five natural products plus four analogs showed pellitorine to be the most active against a variety of insects, but not against a species of snail. B i o l o g i c a l l y a c t i v e isobutylamides have been i s o l a t e d from p l a n t s of the Compositae and the Rutaceae.** Some of the i s o b u t y l a mides were found t o have p a r a l y t i c and t o x i c a c t i v i t i e s against i n s e c t s , e s p e c i a l l y when a p p l i e d t o p i c a l l y to s e v e r a l species of Coleopterans and Dipterans.1>3,4,5 ^ p k describes the i s o l a t i o n , s p e c t r a l i d e n t i f i c a t i o n , s y n t h e s i s , and i n s e c t and s n a i l bioassays of f i v e isobutylamides from the Rutaceae p l a n t , Fagara macrophylla. In a d d i t i o n , the s y n t h e s i s and b i o assay o f f o u r analogs of the isobutylamide n a t u r a l products are described. F. macrophylla i s an East A f r i c a n m e d i c i n a l t r e e known to be r e l a t i v e l y free 'from i n s e c t a t t a c k . In order t o t e s t f o r chemical f a c t o r s i n v o l v e d i n t h i s observed r e s i s t a n c e , p i e c e s o f root bark were e x t r a c t e d w i t h methanol, followed by e v a p o r a t i o n of the methanol and suspension o f the e x t r a c t i n water. A chloroform e x t r a c t i o n o f the suspension was chromatographed on s i l i c a g e l 60 (30-70 mesh ASTM) i n methylenechloride-methanol. Cuts from the s i l i c a g e l column were i n c o r p o r a t e d i n t o a r t i f i c i a l d i e t s optimized f o r s e v e r a l economically-important a g r i c u l t u r a l pest i n s e c t s , the pink bollworm Pectinophora g o s s y p i e l l a , the tobacco budwonn H e l i o t h i s v i r e s c e n s , the corn earworm H. zea and the f a l l armyworm Spodoptera frugiperda.6>7 Monitoring with t h i s a r t i f i c i a l d i e t bioassay, f u r t h e r column chromatography and p r e p a r a t i v e TLC on s i l i c a g e l i n d i e t h y l e t h e r - p e t r o l y i e l d e d f i v e 2

τ

β

r

e

s

e

n

t

w o r

0097-6156/ 84/ 0 2 5 5 - 0 1 6 3 S 0 6 . 0 0 / 0 © 1984 A m e r i c a n C h e m i c a l S o c i e t y

In Pesticide Synthesis Through Rational Approaches; Magee, P., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1984.


164

PESTICIDE SYNTHESIS THROUGH RATIONAL APPROACHES

i n s e c t growth i n h i b i t o r s and/or t o x i c a n t s . The f i v e compounds were i d e n t i f i e d as the isobutylamide compounds fagaramide [N-isobutyl-3-(3,4-methylenedioxyphenyl)-2E-propenamide] (jL), piper1ongumine [ N - i s o b u t y 1 - 5 - ( 3 , 4 - m e t h y l e n e d i o x y p h e n y 1 ) - 2 E , 4 E pentadienamide] ( 2 . ) , 4,5-dihydro-piperlongumine [N-isobutyl-5(3,4-methylenedioxyphenyl)-2E-pentenamide] (.3)» pellitorine ( N - i s o b u t y l - 2 E , 4 E - d e c a d i e n a m i d e ) ( 4 ) , and N - i s o b u t y l - 2 E , 4 E octadienamide ( 5 ) based on spectroscopic and chemical data. In a d d i t i o n , during the course of the i s o l a t i o n of the isobutylamide compounds, the l i g n a n "sesamin" [ t e t r a h y d r o - l , 4 - b i s ( 3 , 4 m e t h y l e n e d i o x y p h e n y l ) - l H , 3 H - f u r o [ 3 , 4 - C ] - f u r a n ] (60 c r y s t a l l i z e d from s o l u t i o n and was s p e c t r a l l y i d e n t i f i e d . Sesamin i s a w e l l known s y n e r g i s t f o r p y r e t h r i n s . ^ The most abundant of the i s o l a t e d amides was fagaramide ( J O . 9 The s t r u c t u r e of fagaramide has long been known,10 but the geometry of i t s s i d e chain double bond has not been c l e a r l y e s t a b l i s h e d . T h i s has now been confirmed as trans based on the l a r g e coupling constant ( 1 6 Hz) i n the 4 0 0 MHz H-NMR spectrum. The a r t i f i c i a l d i e t feeding assay mentioned above was employed to monitor the chromatographic s e p a r a t i o n of the 5 b i o a c t i v e p r i n c i p l e s . Once separated, p u r i f i e d , and s p e c t r a l l y i d e n t i f i e d , the a c t i v e p r i n c i p l e s were synthesized and t e s t e d i n the same a r t i f i c i a l d i e t feeding assay i n order to o b t a i n E D 5 Q - v a l u e s , the e f f e c t i v e doses f o r 5 0 % growth i n h i b i t i o n . The g r o w t h - i n h i b i t o r y a c t i v i t y of the 5 amides on 4 species o f Lepidopteran larvae of a g r i c u l t u r a l importance i s shown i n Table I. P e l l i t o r i n e , the second most abundant amide i s o l a t e d from F. macrophylla, was the most a c t i v e of the i s o l a t e d amides, e s p e c i a l l y against P. g o s s y p i e l l a ( E D 5 Q 1 5 ppm). Pellitorine a l s o caused death ( L U 9 Q = 2 5 ppm) to P. g o s s y p i e l l a larvae, but not to those of H. zea, H. virescens> and 15. f r u g i p e r d a . The i s o l a t e d compound that was c l o s e l y r e l a t e d to p e l l i t o r i n e , N - i s o b u t y l - 2 E , 4 E - o c t a d i e n a m i d e ( 5 ) , a l s o caused m o r t a l i t y t o P. g o s s y p i e l l a only ( L D ^ Q - I O O ppm)· Attempts to synergize the i n s e c t growth i n h i b i t o r y a c t i v i t y of the i s o l a t e d isobutylamides with the c o - o c c u r r i n g sesamin were u n s u c c e s s f u l . Four isobutylamide analogs of the n a t u r a l products were synthesized i n order to compare t h e i r i n s e c t i c i d a l e f f i c a c y with that of the n a t u r a l products. The s y n t h e t i c scheme f o r the p r e p a r a t i o n of cis-fagaramide ( 7 ) i s shown i n Figure 1 . The syntheses of the c i s ( 9 ) and trans ( 8 ) isomers of N - i s o b u t y l cinnamamide were accomplished by procedures s i m i l a r to those u t i l i z e d i n the p r e p a r a t i o n o f the c i s ( 7 ) and trans (I) isomers of fagaramide, with the exception that benzaldehyde was used as s t a r t i n g m a t e r i a l i n the former case, p i p e r o n a l i n the l a t t e r . Isobutylbenzamide ( 1 0 ) was synthesized from benzoyl c h l o r i d e and isobutylamine. Table I shows the growth i n h i b i t o r y a c t i v i t y of the f o u r s y n t h e t i c isobutylamides on the four lepidopterous l a r v a e . The activity of the s y n t h e t i c c i s isomer (7) of fagaramide (JL) was 2 - to 4 - f o l d g r e a t e r , depending on the i n s e c t species t e s t e d , than was fagaramide i t s e l f . Bioassay of s y n t h e t i c amides i d e n t i i

S



5Q-values

are the e f f e c t i v e

210 600 135 720 1000 N.E.

510

H. zea

inhibition.

270 600 175 800 800 N.E.

350 370

Heliothis virescens

doses f o r 50% growth

b

440 430 800 15 70° 135 600 3100 N.E.

Pectinophora gossypiella

LD

v a l u e

t n e

o 0 - v a l u e , the l e t h a l dose f o r 90% death, f o r N-isobutyl-2E,4E-octadienamide a g a i n s t P. g o s s y p i e l l a i s 100 ppm. No l e t h a l e f f e e E was observed T>y any o f the compounds t o 200 ppm a g a i n s t the other t e s t e d i n s e c t s p e c i e s .

b

530 500 1700 230 280 150 270 360 N.E.

Spodoptera frugiperda

I n s e c t Species ( F i r s t I n s t a r )

LDgo> l e t h a l dose f o r 90% death, f o r p e l l i t o r i n e a g a i n s t P. g o s s y p i e l l a i s 25 ppm. ~

ED

Fagaramide (Y) Piperlongumine (2) 4,5-Dihydropiperlongumine (3.) P e l l i t o r i n e (4) N-Isobutyl-2E,4E-octadienamide (5) cis-Fagaramide (7) N-Isobutyl-3-phenyl-2E-propenamide (8) N-Isobutyl-3-phenyl-2Z-propenamide (9) N-Isobutylbenzamide (10)

Compounds

5 0

Table I . I n s e c t growth i n h i b i t o r y a c t i v i t y ( E D i n ppm) o f n a t u r a l isobutylamides and s y n t h e t i c analogs.

a



166

PESTICIDE SYNTHESIS T H R O U G H RATIONAL APPROACHES

Figure 1. The p r e p a r a t i o n of cis-fagaramide (J). The cis-fagaramide (7) was synthesized as o u t l i n e d below. The required a c e t y l e n i c a c i d (c) was prepared from p i p e r o n a l (a) by the Corey's p r o c e d u r e . ^ Treatment of p i p e r o n a l with carbon tetrabromide, triphenylphosphine and z i n c gave the bromo o l e f i n (b) as an o i l i n 71% y i e l d . The bromo o l e f i n (b) was t r e a t e d with 2 equivalents of η-butyl l i t h i u m followed by quenching with dry i c e to give a c e t y l e n i c a c i d (c) i n 54% yield. Treatment of (c) with excess t h i o n y l c h l o r i d e without solvent at 50 °C followed by a d d i t i o n of i s o b u t y l amine i n benzene gave the a c e t y l e n i c amide (d) as a viscous o i l i n 967 yield. P a r t i a l r e d u c t i o n of (d) gave cis-fagarmide (JO i n 897o y i e l d .



10.

κ υ BO ET A L .

167

Isobutylamides from Fagara macrophylla

c a l t o the c i s and trans isomers of fagaramide, but without the methylenedioxy moiety, showed that the trans isomer (8) was from 1 - t o 5 - f o l d more a c t i v e than was the c i s isomer (£) (Table I ) . Except against frugiperda» the removal o f the methylenedioxy moiety decreased the i n s e c t growth i n h i b i t o r y a c t i v i t y (Table I ) . Isobutylbenzamide ( 1 0 ) was found t o be i n a c t i v e as an i n s e c t growth i n h i b i t o r . Thus, the most potent o f the n a t u r a l isobutylamides was p e l l i t o r i n e ( 4 ) , while the most potent o f the s y n t h e t i c isobutylamides was the c i s isomer (7) of fagaramide (I) · Through a comparison o f the a c t i v i t i e s o f the nine n a t u r a l and s y n t h e t i c compounds i n Table I , c e r t a i n f u n c t i o n a l i t i e s appeared to be important i n the e f f i c a c y o f the isobutylamides t o i n h i b i t the growth o f the lepidopterous l a r v a e . These f u n c t i o n a l i t i e s i n c l u d e d the chain length, presence o f the methylenedioxy moiety, the number o f the s i d e c h a i n double bonds, and the stereochemis t r y o f the s i d e c h a i n . Combinations o f these f u n c t i o n a l i t i e s would l i k e l y enhance the a c t i v i t y . F o r i n s t a n c e , Miyakado e t a l . H found that a d d i t i o n o f the methylenedioxy moiety to p e l l i t o r i n e (4) increased i t s t o x i c i t y when t o p i c a l l y a p p l i e d t o adults o f the b e e t l e , Callosobruchus c h i n e n s i s . P e l l i t o r i n e ( 4 ) has long been known f o r i t s t o x i c i t y when t o p i c a l l y a p p l i e d t o a d u l t s o f the b e e t l e , Tenebrio m o l i t o r . l We found that 1 0 pg doses o f t o p i c a l l y a p p l i e d p e l l i t o r i n e caused a p a r a l y t i c a c t i o n on a d u l t s o f the confused f l o u r b e e t l e , T r i b o l i u m confusum (unpublished d a t a ) . However, a l l o f the a f f e c t e d b e e t l e s recovered w i t h i n 2 4 hrs posttreatment. S i m i l a r t o p i c a l a p p l i c a t i o n s o f up t o 2 0 ug/beetle o f fagaramide (1), piperlongumine ( £ ) , and N - i s o b u t y l - 2 E , 4 E - o c t a d i e n a r a i d e ( 5 ) proved ineffective. Previous work with e x t r a c t s o f v a r i o u s p l a n t specie« c o n t a i n i n g isobutylamide compounds i n d i c a t e d the l a r v i c i d a l e f f e c t s o f the e x t r a c t s against s e v e r a l species o f mosquito.1»13 Other work has shown the m o l l u s c i c i d a l a c t i v i t y o f some unsaturated a l i p h a t i c isobutylamides against Physa o c c i d e n t a l i s . l ^ Therefore, we conducted a d d i t i o n a l bioassays o f f o u r o f the F. macrophylla isobutylamides with the house mosquito, Culex p i p i e n s and the freshwater s n a i l , Biomphalaria g l a b r a t u s (Tables I I , I I I ) . Both species are o f medical importance. The l e t h a l a c t i v i t y o f the isobutylamides on £ . p i p i e n s i s shown i n Table I I . The amides were d i s s o l v e d i n 0 . 1 % acetone i n d i s t i l l e d water t o g i v e concentrations of 1 - 2 0 ppm. T h i r d - i n s t a r C. p i p i e n s were t r a n s f e r r e d ( 5 l a r v a e / 1 0 ml t e s t s o l u t i o n ) i n t o 1 oz. p l a s t i c cups using a 1 χ 1 - i n c h c i r c l e o f ordinary window screen. Each treatment was r e p l i c a t e d 4 times and the minimum c o n c e n t r a t i o n o f each compound which caused 1 0 0 % m o r t a l i t y ( L D Q ) w i t h i n 4 8 h at 2 5 ° C and 1 6 L / 8 D photoperiod was deter mined. In a r e s u l t s i m i l a r t o that found with the a r t i f i c i a l d i e t bioassay with lepidopterous l a r v a e , p e l l i t o r i n e proved t o be the most t o x i c of the assayed amides (LDJ^QQ = 5 ppm). 2

1 0


168

PESTICIDE SYNTHESIS T H R O U G H RATIONAL APPROACHES

Natural

Fagaramide

Pellitorine

(A)


(I)

o r N-Isobutyl-2E, 4E-octadienamide

Piperlongumine

(1)

(5)

4,5-Dihydropiper longumine

(1)

d-S es amine (i) Synthetic

cis-Fagaramide

(Z)

N-Isobutylbenzamide (10)

N-Isobuty1-3-phenyl-2Z-prop enamide (9)

N-Isobutyl-3-pheny l-2E-propenamide

(8)


In Pesticide Synthesis Through Rational Approaches; Magee, P., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1984. (LD^^^

a

D

5

pellitorine

m

(pP )

available.

^4,5-dihydropiperlongumine was

not tested due t o i n s u f f i c i e n t

quantities

^ D ^ Q - v a l u e s are the l e t h a l doses f o r 100% death i n a 48-h bioassay.

N-isobutyl-2E,4E-octadienamide

15

10

piperlongumine (2)

(4)

15

^ 100

fagaramide (JL)

(J>)

of n a t u r a l isobutylamides^

larvae of Culex p i p i e n s .

i n ppm)

against t h i r d - i n s t a r

Lethal a c t i v i t y

Compounds

Table I I .



170


The l e t h a l a c t i v i t y of the isobutylamides on B. glabratus i s shown i n Table I I I . M o l l u s c i c i d a l a c t i v i t y was monitored as described p r e v i o u s l y . ^ B r i e f l y , s n a i l s of uniform s i z e s (average diameter of the s h e l l 9 mm) were placed 2 s n a i l s / c o n c e n t r a t i o n i n t o d e i o n i z e d water s o l u t i o n s c o n t a i n i n g known concentrations of the isobutylamides. U n l i k e the r e l a t i v e a c t i v i t i e s of the isobutylamides on the t e s t e d i n s e c t species, fagaramide ( l ) and N-isobutyl-2E,4E-octadienamide (5) were more potent m o l l u s c i c i d e s than were p e l l i t o r i n e (4) or piperlongumine (2). The mode of a c t i o n of the isobutylamides i s unknown, although Miyakado et a l . H found that s e v e r a l isobutylamides ( i . e . p i p e r c i d e and r e l a t e d compounds) caused r e p e t i t i v e discharge when the nerve cord of the cockroach, P e r i p l a n e t a americana was s t i m u l a t e d . We found that fagaramide was i n a c t i v e as an a c e t y l c h o l i n e e s t e r a s e i n h i b i t o r i n an in v i t r o a s s a y ^ (unpublished data) . In summary, we have i s o l a t e d and i d e n t i f i e d through s p e c t r a l data and s y n t h e s i s f i v e n a t u r a l isobutylamides from root bark of Fagara macrophylla as having moderate to weak a c t i v i t y against s e v e r a l species of lepidopterous l a r v a e , a species of l a r v a l mosquito, and a species of s n a i l . In a d d i t i o n , we have attempted to enhance the b i o l o g i c a l a c t i v i t y of the n a t u r a l isobutylamides through synergism and s y n t h e s i s . Although these l a t t e r attempts have not r e s u l t e d i n a compound as potent as the n a t u r a l product p e l l i t o r i n e , they have served to i l l u s t r a t e the importance of c e r t a i n f u n c t i o n a l i t i e s i n the s t r u c t u r e - a c t i v i t y r e l a t i o n s h i p s of the isobutylamides. While the F. macrophylla isobutylamides, e s p e c i a l l y p e l l i t o r i n e , are a c t i v e against s e v e r a l species of pest organisms of medical and a g r i c u l t u r a l importance, t h e i r a c t i v i t y must be enhanced before they can be used on a commercial b a s i s . Hopef u l l y , the r e s u l t s of the present work w i l l d i r e c t future studies l e a d i n g to s y n t h e t i c isobutylamides of s u f f i c i e n t a c t i v i t y to warrant t h e i r p r a c t i c a l use i n i n s e c t and s n a i l c o n t r o l . Acknowledgments I n s e c t s were k i n d l y s u p p l i e d by the agencies of the USDA i n T i f t o n , GA; Phoenix, AZ and B r o w n s v i l l e , TX. The authors thank P r o f e s s o r D. Heyneman f o r B. glabratus supply. T h i s work was p a r t l y supported by a PHS Biomedical Grant to I.K.



(1)

(A)

(2)

a

0

a

i n ppm) of n a t u r a l isobutylamides

LO5Q-values are the l e t h a l doses f o r 50% death.

(5)

m

200

>200

>200

200

k 50 (PP )

n

the s n a i l Bioaiphalaria g l a b r a t u s .

N-isobutyl-2E^,4Ej-octadienamide

pellitorine

piperlongumine

fagaramide

against

D

Lethal a c t i v i t y (^ 5

Compounds

Table I I I .



172

Literature Cited 1.


2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

12. 13. 14. 15. 16. 17.

Jacobson, M. "Naturally Occurring Insecticides"; Jacobson, M.; Crosby, D. G., Eds.; Marcel Dekker, Inc.: New York, 1971; pp. 139-176. Oriowo, M. A. Planta Medica 1982, 44, 54. Su, H. C. F . ; Horvat, R. J . Agric. Food Chem. 1981, 29, 115. Miyakado, M.; Nakayama, I.; Yoshioka, H.; Nakatani, N. Agric. Biol. Chem. 1979, 43, 1609. Kubo, I.; Matsumoto, T.; Klocke, J . Α.; Kamikawa, T. Experientia, in press. Chan, B. G.; Waiss, A. C. J r . ; Stanley, W. L . ; Goodban, A. E. J . Econ. Entomol. 1978, 71, 366. Kubo, I.; Klocke, J . A. in "Plant Resistance to Insects"; ACS Symposium Series 208, American Chemical Society: Washington, D.C., 1983; pp. 329-346. Casida, J . E. "Pyrethrum, the Natural Insecticide"; Academic Press: New York, 1973. Fish, F . ; Waterman, P. G. Phytochemistry 1972, 11, 3007. Thoms, H.; Thumen, F. Chem. Ber. 1911, 44, 3717. Miyakado, M.; Nakayama, I.; Inoue, Α.; Ohno, N.; Yoshioka, H. "Pesticide Chemistry"; Abstracts of the Fifth Inter national Congress of Pesticide Chemistry (IUPAC), Kyoto, Japan, 1982, Abstract No. IIIc-28. Crombie, L. J . Chem. Soc. 1955, 999. Srivastava, J . B. Indian J . Exptl. Biol. 1970, 8, 224. Johns, T.; Graham, K.; Towers, G. H. N. Phytochemistry 1982, 21, 2737. Nakanishi, K.; Kubo, I. Israel J . Chem. 1978, 16, 28. Ellman, G. L.; Courtney, K. D.; Andres, V. J r . ; Featherstone, R. M. Biochem. Pharmacol. 1961, 7, 88. Corey, E. J.; Fuchs, P. L. Tetrahedron Letters 1972, 3769.

RECEIVED April 10, 1984


Pesticide Synthesis Through Rational Approaches - American

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