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Identification and synthesis of some fatty acidderivatives from larvae of Chilecomadia valdiviana(Lepidoptera: Cossidae)

To cite this Article: Bergmann, Jan, Lopez, Katya and Buono-Core, Gonzalo ,'Identification and synthesis of some fatty acid derivatives from larvae of Chilecomadia valdiviana (Lepidoptera: Cossidae)', Natural Product Research,

21:5, 473 - 480To link to this article: DOI: 10.1080/14786410601129986URL: http://dx.doi.org/10.1080/14786410601129986

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Natural Product Research , Vol. 21, No. 5, 1 May 2007, 473–480

Identification and synthesis of some fatty acid derivatives fromlarvae of Chilecomadia valdiviana (Lepidoptera: Cossidae)

JAN BERGMANN*, KATYA LOPEZ and GONZALO BUONO-CORE

Instituto de Quı ḿica, Pontificia Universidad Cato ĺica de Valparaı śo,Avda Brasil 2950, Valparaı śo, Chile

(Received 25 January 2006; in final form 17 May 2006 )

Larvae of Chilecomadia valdiviana (Lepidoptera: Cossidae) were extracted and the extract wasfractionated by chromatography on silica. As shown by gas chromatography–mass spectro-metry, the major fraction contained saturated and unsaturated straight-chain acetates, with(Z )-5,13-tetradecadienyl acetate and dodecyl acetate as the main components, while in a minorfraction the corresponding alcohols were detected. The identification of the compounds and thesynthesis of some reference material are presented.

Keywords: Chilecomadia ; Cossidae; Larvae; Acetates; DMDS; GC/MS

1. Introduction

The carpenterworm Chilecomadia valdiviana (also known as butterworm) is apolyphagous insect native to Chile. It is associated with bushes and trees, amongthem economically important species like eucalyptus or avocado trees. The larval stagefeeds on the wood of the host species, boring galleries of up to 27 cm length and 1 cmdiameter into the stem [1], weakening the bole and making it more susceptible to windbreakage. Studies of other cossid species revealed that larvae commonly produce fattyacid derivatives, similar to the sex pheromone compounds produced by adult females[2–4]. In the course of a study aimed at the identification of the sex pheromone of C. valdiviana , we therefore also analyzed the composition of volatile compoundsproduced by the larvae.

2. Results and discussion

Larvae of C. valdiviana were homogenized and extracted with hexane. The extract wasfiltered and concentrated to give the crude extract, which was fractionated by flashchromatography on silica gel, yielding two fractions. Fraction 1 contained the vast

*Corresponding author. Tel.: þ 56-32-273172. Fax: þ 56-32-273422. Email: [email protected]

Natural Product ResearchISSN 1478-6419 print/ISSN 1029-2349 online 2007 Taylor & Francis

http://www.tandf.co.uk/journalsDOI: 10.1080/14786410601129986

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majority (82%) of the material extracted and consisted of straight-chain acetates, whilein fraction 2 about 1% of the crude extract was recovered, corresponding to straight-chain alcohols. The remaining material did not elute from the column under the chosenconditions.

One of the major components in fraction 1 was identified as dodecyl acetate, bycomparison of the analytical data with those of an authentic standard. The remainingcompounds were mainly singly and doubly unsaturated acetates, as deduced from theirmass spectra. In order to determine the positions of the double bonds, the extract was

submitted to derivatization with dimethyl disulfide (DMDS). The formation of DMDSadducts leads to prominent fragments in the mass spectrum, allowing the unequivocaldetermination of double bond positions [5,6]. The results of these analyses aresummarized in table 1.

Fraction 2 contained five compounds, one of which was shown to be dodecanol bycomparison with an authentic standard. The remaining compounds were twododecenols, a tetradecenol, and a tetradecadienol. Upon comparison with the referencematerial synthesized, the C 14 compounds were identified as ( Z )-5-tetradecenol ( 13) and(Z )-5,13-tetradecadienol ( 9), while the remaining two C 12 compounds are likely to bethe corresponding alcohols of 5-dodecenyl acetate and 11-dodecenyl acetate.

To determine the geometry of the double bonds in the two major unsaturatedcompounds, 5,13-tetradecadienyl acetate and 5-tetradecenyl acetate, and in thecorresponding alcohols, reference material was synthesized. The general procedure isshown in scheme 1. Key steps are the acetylenic coupling of protected 5-hexyn-1-ol ( 6)with 8-bromo-1-octene and 1-bromooctane, respectively, and the selective partialreduction of the triple bond to a double bond with the desired geometry.Hydrogenation of tetradec-5-yn-13-en-1-ol ( 8) with Lindlar’s catalyst at 1 bar inorder to obtain ( Z )-5,13-tetradecadienol ( 9), resulted, however, in a mixture of products, with ( Z )-5-tetradecenol as the main component. The terminal double bond isapparently more susceptible to reduction than the internal triple bond, as the result wasnot altered by shortening the reaction time to 10 min. Determination of the naturalcompound’s geometry, however, was still possible by using the synthesized ( E ) isomer,as this contained small amounts of the ( Z ) isomer. Comparison of the analytical data of the synthetic reference material with those of the natural compounds clearly showed the

Table 1. Straight-chain acetates identified from larvae of C. valdiviana .

No. Compound Relative percentage

1 5-Dodecenyl acetate 1.6

2 7-Dodecenyl acetate 0.13 11-Dodecenyl acetate 1.54 Dodecyl acetate 375 Tetradecatrienyl acetate 0.16 (Z )-5,13-Tetradecadienyl acetate ( 1) 447* 7,13-Tetradecadienyl acetate Aprox. 0.18 (Z )-5-Tetradecenyl acetate ( 3) 149* 7-Tetradecenyl acetate Aprox. 0.6

10 9-Tetradecenyl acetate 0.211 13-Tetradecenyl acetate 0.212 Tetradecyl acetate 1.1

*Identified in DMDS-derivatized extract; co-elutes with previous peak in analysis without derivatization.

474 J. Bergmann et al.

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natural compounds to present ( Z ) geometry. Pure ( Z )-5,13-tetradecadienyl acetate hasbeen obtained before by copper-catalyzed carbon–carbon coupling [7].

Similar compounds have been found in larvae of other cossid species. 5,13-Tetradecadienol, 3,5,13-tetradecatrienol, and 4,6,13-tetradecatrienol, together with thecorresponding acetates have been identified from Cossus cossus larvae, without

determining the geometry of the double bonds [2]. In larvae of Zeuzera pyrina , dodecylacetate, 11-dodecenyl acetate and 5,13-tetradecadienyl acetate were identified [3].Larvae of Chilecomadia moorei , a species closely related to C. valdiviana , producedodecyl acetate, ( Z )-5-dodecenyl acetate, ( Z )-7-dodecenyl acetate, 11-dodecenylacetate, tetradecyl acetate, ( Z )-4-tetradecenyl acetate, ( Z )-5-tetradecenyl acetate, and(Z )-5,13-tetradecadienyl acetate [4]. A common feature in all species investigated, is theproduction of 5,13-tetradecadienyl acetate, which is also the main component in C.valdiviana . Probably, the enzymes involved in the biosynthesis of these straight-chainacetates, are conserved in the family Cossidae, thus leading to secretions similar incomposition. The function of these secretions is not known. It can be speculated thatthey might possess antimicrobial properties or that they are used by gravid femaleadults at the moment of choosing an oviposition site. This would explain the fact thatinfestations with C. valdiviana occur concentrated in a small area within a bigger area of available host plants.

RO

O

R O

O

OH OTHP

OTHP

R

ROH

R OH

OH

R

(5) (6)

(7) R = 7-Octenyl(11) R = n -Octyl

6

a

b

ed

c

f

a: DHP, p TsOH, RT; b: BuLi, 8-bromo-1-octene or 1-bromooctane, THF, HMPT, –30 ° C;c: p TsOH, MeOH, RT; d: H2, Lindlar's catalyst, hexane, RT; e: Ac 2O, DMAP, pyridine, RT;f: LiAlH4, diglyme, 200

° C

8, 12

8, 12e






Scheme 1. Synthesis of reference material.

Fatty acid derivatives from larvae of C. valdiviana 475

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In the species C. cossus and Z. pyrina , the compounds produced by adult females aredifferent from those identified from the larvae. The sex pheromone of C. cossus consistsof (Z )-5-dodecenol, ( Z )-5-dodecenyl acetate, and ( Z )-5-tetradecenyl acetate [8], while

in Z. pyrina (E ,Z )-2,13-octadecadienyl acetate, ( E ,Z )-3,13-octadecadienyl acetate,(Z ,Z )-2,13 octadecadienyl acetate, and ( Z )-13-octadecenyl acetate are biologicallyactive compounds produced by females [9]. There is no information about volatilecompounds of C. moorei , however, these are likely to be different as well, as none of thecompounds present in larvae were found in the pupae [4]. Apparently, biosyntheticpathways are different in larval and adult stage, respectively. It is interesting to note,however, that the preferred positions of insaturations are at carbons 5 and 13, both inadults and larvae. Identification of the compounds produced by adult C. valdivianamight reveal more coherences.

3. Experimental section

3.1. General experimental procedures

Solvents and chemicals were purchased from Merck (Darmstadt, Germany) andSigma-Aldrich (St. Louis, USA). Chemicals were of highest available purity and used assupplied, solvents were dried and distilled prior to use.

Silica gel for column chromatography was from Merck (silica gel 60, 63–200 mm;silica gel 60, 32–63 mm for flash chromatography).

Gas chromatography–Mass spectrometry (GC/MS) analyses were carried out ona Shimadzu GC-17A–GCMS-QP5050A combination. The GC was equipped witha 30m 0.25 mm HP-5 fused silica capillary column (0.25 mm film thickness). Massspectra were acquired at 70 eV.

Proton NMR spectra were acquired on a Bruker AMX400 at 400MHz. Chemicalshifts are expressed in ppm relative to the internal standard tetramethylsilane( ¼ 0 ppm).

3.2. Insect material

Larvae of C. valdiviana were collected from infested trees in Parque Nacional LaCampana (Regio ń de Valparaı śo, Chile) and other sites around Valparaı śo.Identification was done according to reference [10].

3.3. Extraction and fractionation procedure

100 g larvae (all instars) were homogenized and stirred with 500 mL of hexane overnightat ambient temperature. The resulting mixture was filtered and dried over anhydrousmagnesium sulphate. The solvent was evaporated to give 12.0g of crude extract, whichwas fractionated by flash chromatography on 200g of silica gel, using a mixture of hexane–ethyl acetate (85 : 15) as the eluent. Two fractions were collected; fraction 1(9.92g) and fraction 2 (0.09 g). These fractions were submitted to analysis as described.


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3.4. Derivatization with DMDS

In a gas-tight vial, 50 mL of carbon disulfide, 5 mL of iodine solution (5% in diethylether), and 50 mL of DMDS were added to 50 mL of the extract. The vial was placed inan oven at 50 C for 4 h. Sodium thiosulfate solution (10%) was added to destroyexcess iodine; the organic phase was carefully removed, concentrated, and analyzed byGC/MS.

3.5. Syntheses of reference compounds

Synthesis of 1-(2 0-tetrahydropyranyloxy)-5-hexyne (6). To a stirred solution of 4.00 g(40.8 mmol) 5-hexyne-1-ol in 20mL dry dichloromethane were added 150 mg p-toluenesulfonic acid and 3.72 mL (3.44 g, 41 mmol) 3,4-dihydro-2 H -pyrane at 0 C.

The reaction mixture was allowed to warm to room temperature and hexane and sat.sodium bicarbonate were added. The aqueous phase was extracted with hexane; andthe combined organic phases were dried (MgSO 4 ) and concentrated. Purification of thecrude product by column chromatography yielded 7.41 g (99%) of 6 as a colorless oil;MS (EI, 70 eV): m/z ¼ 41 (52), 56 (45), 67 (28), 79 (35), 85 (100), 101 (22), 111 (4), 125(2), 140 (1), 181 (1), 182 (M þ ,

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43 (44), 55 (66), 67 (48), 68 (35), 79 (100), 81 (35), 94 (28), 97 (38), 111 (15), 112 (10),121 (2), 124 (2), 135 (2), 138 (2), 153 (1), 166 (2), 192 (1), 210 (M þ ,

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Synthesis of ( E )-5-tetradecenyl acetate (4). The synthesis was essentially the same asfor 3. Acetylation of 100 mg (0.47 mmol) 14 with 0.50 mL (0.54 g, 5.3 mmol) aceticanhydride yielded 110 mg (92%) of a colorless oil; purity (GC): 94% ( E ), 6% ( Z ); MS

(EI, 70 eV): m/z ¼ 41 (50), 43 (100), 54 (50), 55 (52), 61 (3), 67 (80), 68 (54), 81 (62), 82(73), 95 (43), 96 (49), 109 (12), 110 (14), 123 (8), 124 (10), 138 (10), 151 (2), 166 (5), 194(12), 254 (M þ ,

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J ¼ 6.6 Hz, H-1), 2.08–1.94 (m, 6H, H-4, H-7, H-12), 2.04 (s, 3H, CH 3 CO), 1.66–1.58(m, 2H), 1.44–1.24 (m, 10H).

Acknowledgements

Jan Bergmann would like to thank the ‘‘Direccio ń de Investigacio ń’’ of PUCV for aresearch grant (DI 125.789). Katya Lopez thanks MECESUP (Chile) for a doctoralfellowship. The support of Corporacio ń Nacional Forestal (Vin ã del Mar, Chile) isacknowledged.

References

[1] J.T. Kliejunas, B.M. Tkacz, H.H. Burdsall Jr, G.A. DeNitto, A. Eglitis, D.A. Haugen, W.E. Wallner.Pest risk assessment of the importation into the United States of unprocessed Eucalyptus logs and chipsfrom South America. Gen. Tech. Rep. FPL-GTR-124, U.S. Department of Agriculture, Forest Service,Forest Products Laboratory, Madison, WI (2001).

[2] R. Trave, L. Garanti, A. Marchesini, M. Pavan. Chim. Ind. , 11 , 1167 (1966).[3] A. Marchesini, L. Garanti, M. Pavan. Ric. Sci. , 39 , 874 (1969).[4] J.A. Garbarino, V. Gambado. Bol. Soc. Chil. Quı ´ m, 33, 129 (1988).[5] H.-R. Buser, H. Arn, P. Guerin, S. Rauscher. Anal. Chem. , 55, 818 (1983).[6] M. Vincenti, G. Guglielmetti, G. Cassani, C. Tonini. Anal. Chem. , 59, 694 (1987).[7] G. Cahiez, A. Alexakis, J.F. Normant. Tetrahedron Lett. , 21, 1433 (1980).[8] A. Capizzi, C. Tonini, E. Arsura, G. Guglielmetti, P. Massardo, P. Piccardi. J. Chem. Ecol. , 9, 191 (1983).[9] P.L. Castellari. Boll. Ist. Ent. Univ. Bologna , 40, 239 (1986).

[10] A.O. Angulo, T.S. Olivares. Gayana Zool. , 56, 181 (1992).


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