Localization of double and triple bonds in linear conjugated enyne-acetates and alcohols

Localization of Double and Triple Bonds in Linear Conjugated Enyne-acetates and Alcohols

J. Einhornt INRA-CNRS, Laboratoire des Mtdiateurs Chimiques, Domaine de Brouessy, Magny-Les-Hameaux, 78470 Saint Rtmy-les-Chevreuse, France

H. Virelizier

A. Guerrero

J. C. Tabet Laboratoire de Synthtse Organique, Ecole Polytechnique, 91228 Palaiseau, France

SEAIN-CEA, Saclay, 91 191 Gif-sur-Yvette, France

Instituto de Quimica Bio-Organica, CSIC, Jorge Girona Salgado, 18-26, Barcelona-34, Spain

Localization of double and triple bonds in linear conjugated enyne-acetates and alcohols can be achieved in microgram scale through a two-step reaction sequence: epoxidation followed by catalytic hydrogenation or deuteration. This derivatization yields a saturated secondary alcohol of RCHOH(CH2),0R'type (R = CH3(CH2),, R' = H, COCH3), by regiospecific ring opening reaction of the intermediate epoxide. The position of the hydroxyl group is clearly defined by the [M-R]+ and subsequent ions observed in the electron impact (EI) mass spectrum. The unequivocal location of the conjugated enyne system can be effected by comparing the pattern and position of the IM - Rl+ ion@) found under hydrogenation and deuteration conditions, since the same secondary alcohol may proceed from two isomeric enyne structures, i.e. CH3(CH2),CH=CH-C-C-(CH2),-30R' (enyne A) and CH3(CH,),-3C~C-CH=CH(CH,),0R' (enyne B). Metastable (mass-analysed ion kinetic energy (MIKE), HV scan) mass spectra and gas phase labelling were used for filiation attribution and mechanisms.

INTRODUCTION

Pheromones are biologically active chemicals which are generally released by living organisms for intraspecific communication. Among them, sex pheromones have received considerable attention especially in Lepidop- tera for their use in plant protection."' In this context, we have recently identified the major component of the sex pheromone of the processionary moth Thaumetopoea pityocampa (Denis and Schiff) as (2)-13-hexadecen-l1- yn- 1-yl acetate ( 1),3 which represents the first example of a new class of compounds in the pheromone field. This work led us to develop a highly efficient and sensi- tive method for localization of double and triple bonds in long chain conjugated enyne-alcohols and acetates.

Location of double bond(s) in long chain mono- (or po1y)ethylenic fatty acid derivatives generally involves der i~a t iza t ion~-~ or oxidative degradation' followed by mass spectral analysis. Similarly, a few8,9methods have been reported for triple bond location. A double or triple bond may be also localized directly by mass spectrometry through ion-molecule reactions."-" However, only one (degradative) methodI3 has been proposed for specific enyne assignment in a linear long chain struc- ture, but it does not concern conjugated systems.

The procedure we report herein allows location of a conjugated enyne system after a one-vial two-step derivatization reaction: ( 1) epoxidation (m-chloroperbenzoic acid (m-CPBA) in CH,Cl,) and (2) catalytic hydrogenation ( €'toz in MeOH) or deuteration (PtO, in

t Author to whom correspondence should be addressed.

MeO'H). The El mass spectrum of the saturated secondary alcohol thus obtained yields the required information to assign unequivocally the position of the initial enyne. The metastable decompositions have been studied to determine precisely the origin of the main characteristic ions produced under conventional and source H/2H exchange conditions.

EXPERIMENTAL

Mass spectra were recorded on a Nermag R-10-10 gas chromotograph-mass spectrometer equipped with a 25 m X0.25 mm i.d. CPtm Sil 5 (Chrompack, Middel- burg, the Netherlands) capillary column and using helium as carrier gas. Column oven temperature was maintained between 150 and 220 "C depending on the substrate. Injector block (Ross injection system) and transfer line temperatures were 240 "C and 270 "C respectively, while the ion source temperature was 110 "C. Mass spectra were recorded at an electron energy of 70eV in the EI mode and 95eV in the chemical ionization (CI) mode. Data acquisition and reduction were performed by a SIDAR gas chromatographic/mass spectrometric data system. The metastable decompositions were studied with a VG ZAB/2F instrument. Under conventional EI conditions, the high voltage (HV) scan14 spectra were recorded under 5 kV as accelerating voltage for the daughter ions, whereas the mass-analysed ion kinetic energy (MIKE)" spectra were performed at 8 kV. The source H/,H exchange reactions were carried out by introduction of 'H20 via the inlet liquid system.

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200 BIOMEDICAL MASS SPECTROMETRY, VOL. 12, NO. 5, 1985 @ Wiley Heyden Ltd, 1985

LOCALIZATION OF DOUBLE AND TRIPLE BONDS

I OH

18

Scheme 1. Regioselective derivatization of enyne 1 to alcohol 18

Chemicals

Hexane and methylene chloride (pesticide grade) were obtained from Mallinkrodt Inc. (St Louis, Missouri) and methanol (99.8%) from Prolabo (Paris) and were used without further purification. Monodeuterated methanol (CH30’H, 99%’H), deuterium oxide (’H’O, 99.89%2H) and deuterium (2H2, 99.75% 2H) were purchased from the CEA (Saclay, France), whereas hydrogen (99.8%) was from Air Liquide (Paris). m-Chloroperbenzoic acid (m-CPBA, S5YO) and platinum dioxide (SO0/, Pt) were provided by Janssen Chimica (Beerse, Belgium) and Fluka AG (Buchs, Switzerland) respectively.

The conjugated enynes were prepared by already reportedI6 methods and purified accordingly to yield the required pure 2 or E isomers.

Derivatization

Each sample to be analysed, ranging from 200ng to 10 pg, initially dissolved in 10 pl of hexane, was diluted with 40-60 p1 of methylene chloride. To this solution a few crystals of m-CPBA (cO.1 mg) were added and the mixture was stirred at room temperature until complete disappearance of the starting material (10-30 min, gas chromatography/mass spectrometry (GC/MS)). Half the volume was then diluted with about the same volume of MeOH or Me02H and subjected to microhydrogena- tion or microdeuteration in the presence of a minute amount (<0.1 mg) of Pt02 as catalyst for 30-60 s with stirring. The crude sample, eventually filtered and con- centrated under a stream of Nz, was immediately analysed by GC/MS under EI and CI conditions. The complete sequence was carried out in a 1 ml open-top Teflon-lined screw cap vial (Kontes, Vineland, New Jersey). For the second step, two syringe needles were inserted into the vial cap to allow free flow of hydrogen (or deuterium) gas. The enyne derivatives used in the metastable decomposition studies were prepared in a milligram scale; the intermediate cis/ trans epoxides were isolated and subsequently submitted to catalytic hydrogenation. The resulting secondary alcohols were purified by recrystallization in a suitable solvent or chromatographed on silica gel.

RESULTS AND DISCUSSION ~ ~ ~~ ~~ ~~

According to our observations, EI mass spectra of conjugated enynes and EI or CI mass spectra” of their epoxides seldom give sufficient structural information for the rapid localization of the enyne group in the molecule. However, we have found that epoxidation of

a conjugated enyne (i.e. 1, Scheme I , Table l ) , followed by catalytic hydrogenation furnished a saturated secondary alcohol in a yield (2O-80%, gas chromatographic estimation) which depends on the substrate. As is shown later, El mass spectrum of the alcohol and comparison with that obtained when hydrogenation is replaced by deuteration affords unambiguous assignment of the enyne position in the initial molecule. The formation of the alcohol can be postulated by a regiospecific ring opening reaction of an intermediate unsaturated epoxide during the hydrogenation process.

This reaction does not depend on the terminal function ( 14-hydroxyhexadecane is obtained from (2)- 13- hexadecen- 1 1-yne) but necessitates conjugation of the enyne system (epoxide function recovered unchanged after epoxidation/hydrogenation of ( E )-4-nonen-7-yn- 1-yl acetate), thus demonstrating the assisted epoxide ring opening by the triple bond.

By GC/MS we have identified, as side reaction products (at lower retention times in our gas chromatographic conditions), the saturated straight chain alcohol or acetate (i.e. hexadecan-1-yl acetate (32) from 1) and, generally in very low yield, the saturated epoxide (i.e. 13,14-epoxyhexadecan- 1 -yl acetate (33) from 1) (Fig. I ) .

18

7- T L 5 6 7 8 9

rnin.

Figure 1. Gas chromatographic/mass spectrometric chramata- gram (total ionic current; CPtmSil 5,25 m, 210 “C) of crude derivat- ized (epoxidation/hydrogenation) enyne 1. 18= 14-hydroxyhexadecan-I-yl acetate; 32 = hexadecan-I-yl acetate; 33: 13,14- epoxy-hexadecan-I-yl acetate.

BIOMEDICAL MASS SPECTROMETRY, VOL. 12, NO. 5, 1985 201

J. EINHORN, H. VIRELIZIER, A. GUERRERO AND J. C. TABET

Table 1. Conjugated enynes and their corresponding secondary alcohols after the epoxidation/hydrogenation reaction Stereo

MOI. Molecular chemist$

Conjugated enynes Compound wt formula m n R' (double bond)

1 278 C18H3002 1 13 AC z

3 236 Cl6HZ8O 1 13 H Z 4 278 ClaH3002 1 13 AC E 5 222 C14H2202 1 9 AC z

6 278 C18H3002 6 8 AC E 7 236 Cl6HZ80 6 8 H E 8 278 C18H3002 5 9 AC E 9 236 Cl6HZ80 5 9 H E

11 250 C,6H2602 4 8 Ac E

14 194 C13H2.O 4 7 H E 15 222 C,4H2202 4 6 Ac E 16 180 Cl2HZ00 4 6 H E 17 222 Cl4HZ2O2 4 6 Ac Z

C l I 3 l L t l * ) m 2 292 C19H3202 1 13 COEt Z

z i i i ~ , ) ~ _ , i n ' 10 278 C18H3002 7 7 AC

t L l l j l c l 121m~

( C I I > I ( P I < ' l2 208 C14H240 E E - r 7 13 236 C15H,,02 4 7 Ac

Mol Alcohols Compound wt

18 300 19 314

Oli 20 258 18 300 21 244

n c i i j ( i i l Z ) m 26 300

R C I I I L ' 1 2 1 , , 0 R '

22 23 24 25 27 28 29 30 31 32 31

300 258 300 258 272 230 258 21 6 244 202 244

Molecular formula n R R'

Cl8H3,O3 13 C2H5 AC C19H3B03 13 C2H5 COEt

C1,H3,O3 13 C2H5 Ac C16H3402 13 C2HS H

C14H2803 C2H5 Ac CisH3603 7 C8H17 Ac

a Derivatization of corresponding 2 and E enynes led to the same alcohol in not significantly different yields.

8 C,H15 Ac

9 C6H13 Ac

8 C5Hll Ac

7 C5H,, Ac

6 C5Hll Ac

6 C5Hll Ac

8 C,H15 H

C6H13

C5H11

C 5 H l l

6 C5Hll H

In most of the examples studied 200 ng of compound were sufficient to determine unequivocally the location of the enyne function. However, for the structural deter- mination of the processionary moth p h e r ~ m o n e , ~ approximately 1 pg of active material was used (Fig. 2(d)).

Mass spectra of the alcohol derivatives

The derivatization method described above has been successfully applied to several synthetic straight chain conjugated enyne-acetates and enyne-alcohols (Table 1). The compounds examined ranged from C,, to C16, the enyne functionality being oriented in the two possible ways relative to the terminal function.

The Cl.NH3 spectra of the secondary alcohols showed the expected [M + NHJ, [M + HI+ and [M + H - H20]+ ions which confirmed their corresponding molecular weights and the presence of a hydroxyl group. On the other hand, the El mass spectra gave significant clues about the location of the secondary hydroxyl group. Thus the EI mass spectrum of the hydroxy acetate 18 ([MI+', m / z 300 not observed) includes the useful frag- ment ions at m / z 271, 211, 193 and 182 (Fig. 2 (a)).

The abundant ion at m / z 271 is produced by loss of a C2H; radical from the molecular ion a ([MI+', m / z 300). This elimination can occur either by direct a-hydroxy cleavage through mechanism (1) (ion b, Scheme 2) or after (or simultaneously with) a long range hydrogen rearrangement from the labile hydroxy- lic hydrogen to the acetoxy group through mechanism (2) (ion b', Scheme 2).

The ions b and/or b' (m/z 271) may liberate an acetic acid molecule giving rise to the formation of the same ion d [M-C2H;-AcOH]+ ( m / z 211), which can then eliminate water (ion f, m / z 193). This assumption was demonstrated by using source H/'H exchange conditions in which EI mass spectrum of 18 showed a peak

at m / z 272, corresponding to ion b (or 6') ( m / z 271 shifted by 1 u), with no other peak shifted. This observa- tion is in agreement with the hypothesis of a specific O H (or O'H) transfer-taking place from ion b at the latest-to the acetate group, which induces its elimination, giving rise to ion d [M - C2H; - AcOH]+ (or [ MzH - C2H; - AcO'H]+) ( m / z 21 1). The acetic acid elimination can then be followed by the loss of water to produce ion f (C,,H,,)+ ( m / z 193).

The origin of ions at m / z 193 (j') and 211 ( d ) (or homologous ions from the hydroxy acetate 24) was confirmed by the HV scan spectra (Table 2) which, respectively, showed as precursor ions, m / z 21 1 (not shifted under source H/'H exchange) and m / z 271 (or m / z 272 under source H/2H exchange conditions). Fur- ther evidence of this fragmentation sequence was given by MIKE spectra studies (Table 3), which also clearly indicated successive losses of AcOH and H 2 0 from [M-C,H;]+ ( m / z 271) and the homologous [M - R.]+ ionfrom the hydroxyacetate24[M -C,H;,)+ ( m l z 215).

In the case of 18, for instance, the main daughter ions of ion m/z271 are found at m/z211 [M-C2H;- AcOH]+ and m / z 193 [M -C2H; -AcOH - H20]+, the latter being the main daughter ion for ion m / z 21 1. Daughter ions of less abundance such as m / z 151, 137, 123, 111, 109, 97 and 95, observed in the metastable decomposition of both ions m / z 271 and 21 1, are also present in the conventional EI spectrum of 18.

The radical-ion (C13H26)+' ( m / z 182) was not observed in any of these MIKE spectra. However, a precursor ion at m/z242 (or m/z243 under source H/,H exchange), which turned out to be too weak to be detected in the conventional EI mass spectrum (Fig. 2(a)), was evident from the HV scan spectra (Table 2). Therefore, radical-ion m / z 182 was postulated to be produced by specific elimination of AcOH (or AcO'H) from the unstable ion m / z 242 (or m / z 243 under labelling conditions), which is probably itself generated from the molecular ion by loss of propionaldehyde ( a ' -

202 BIOMEDICAL MASS SPECTROMETRY, VOL. 12, NO. 5, 1985

m/z

Figure 2. El mass spectra of the secondary alcohols 18, 24 and 25, obtained, respectively, from enynes 1 or from natural sex pheromone of the processionary moth, 8,9. (a) 14-Hydroxyhexadecan-I-yl acetate (18). (b) 10-Hydroxyhexadecan-I-yl acetate (24). (c) 10-Hydroxyhexadecan-I- 01 (25). (d) 14-Hydroxyhexadecan-I-yl acetate (18) (from 1 kg natural compound 1).

Table 2. HV scana spectra of ions at m / z 211, 193 and 182 from hydroxy acetate 18 and their homologous ions at m/z 155, 137 and 126 from 24

Daughter ions (main beam, m i l ) Precursor ions

Hydroxy awtate 18

21 1 193 1 82b 242[M -C,H60]+' (100%)

271 [M - CZHJ+ (100%) 271 [M - CzH;]+ (1 5%) 21 1 [ M - CZH; - AGOHI+ (85%)

Hydroxy acetate 24 mI2

155 215 [M - C6H (100%) 137 1 26b

215 [M - C6H;,]+(4%) 186 [M - C,H140]+' (100%)

155 (M - C,H;, -AcOH]+ (96%)

a Each HV scan normalized to 100% of the total metastable ion current. Under source H/*H exchange conditions the precursor ion was shifted by +1 u.


J. EINHORN, H. VIRELIZIER, A. GUERRERO AND J. C. TABET

H transfer direct a[q" ( m / z 3C0 or 301)

a-cleavage

+ Q

'H ('H) b m / z 271 (or 272) -

H transfer

I

" ) y % 6 \ L C 0 A

m* I - AcoH(2HH) &

/ a-cleavage

[ Ac ] .

a' -cleavage I F H )

c m / Z 242 (or 243) -

m* 1 - AcoH(2H'

- f m/z 193

Scheme 2. Molecular decomposition of the hydroxy acetate 18.

Table 3. MIKE spectra" of IM-C,H;]+ (m/z 271) and IM- C,H;-AcOH]+ (mIz211) from 18 and the homologous ions formed from 24

Compound 18 Compound 24 Daughter Main Beams Daughter Main Beams

ions 271 21 1 ions 215 155

253 3 197 5.7 229 3 173 2.6 21 1 100 155 100 193 56 100 137 80 100 151 2.1 4.2 97 2.9 3.6 137 6.4 12.7 95 8.6 11 123 4.8 8.8 83 2.8 3.7 111 4.2 7.3 81 14.3 19.3 109 2.7 5.8 97 2.1 4.3 95 1.7 3.5 83 0.7 1.5 81 0.7 1.2

a Abundances given relative to that of the main daughter ion (100%).

cleavage by mechanism 2, Scheme 2 ) after O H (or O ' H ) transfer to the acetate group. The existence of such a mechanism, which indicates that the O H rearrangement may take place from the radical-ion a ( [MIC') , can be used to explain the cleavage fragments. In fact, the absence of loss of water from ion m / z 271 ( b or b' in Scheme 2) in the source (or its very low abundance in the metastable region) suggested that the protonated acetate (ion b') was almost uniquely produced rather than the protonated aldehyde b.

This assumption was verified by examining the uni- molecular (MIKE) or collisional activated decomposition (CAD) ofthis ion, directly produced by protonation (Ci isobutane) of long chain aldehyde-acetates (i.e. 10-acetoxy-I-decanal, m / z 215 for [M+ HI'). Under both conditions, competitive losses of H,O and AcOH were observed (the ion [M+H-H,O]' was also abundant in the conventional mass spectrum). The presence of two species of types b and b' is in agreement with the close gas phase proton affinitie~".'~ of the acetate and aldehyde groups. These experiments indicating that


LOCALIZATION OF DOUBLE AND TRIPLE BONDS

Table 4 Relative abundances ("10) of the main ions in the EI mass spectra of the secondary alcohols derived from enynes 1-17

Compound Mw [ M - R ] + [M - R ' - H,Ol+ [M-R'-AcOH)+ [M-R.-2H,OJt [M-R -AcOH-H,O]+ [M-RCHO-AcOHJ '

18 (l)a 300 271 (22) 211 (4) 193 (4) 182(11) 19 314 285 (14) 211 (3.5)b 193 (2)b 182 (4.5)b 20 258 229 (14.5) 211 (5.5) 193 (4.5) 18 (4)" 300 271 (27) 211 (6) 193 (4) 182 (16)

126(18.5) 21 244 215 (22) 155 (6) 137 (18) 22 300 201 (18) 141 (4.5) 123 (32) 112 (23.5) 23 258 159 (27) 141 (9.5) 123 (72) 24 300 215 (48) 155 (6) 137 (15) 126 (17) 25 258 173 (22) 155 (3) 137 (17) 26 300 187 (32) 127 (26.5) 109 (89) 98 (60) 27 272 201 (19.5) 141 (5.5) 123 (32) 112 (20.5) 28 230 159 (18.5) 141 (5) 123 (37) 29 258 187 (13.5) 127 (12) 109 (70) 98 (38) 30 216 145 (14) 127(11.5) 109 (100) 31 (15)' 244 173 (14.5) 113(44.5) 95 (1 00) 84 (57.5)

31 (17)8 244 \73(16) 113 (44) 95 (100) 84 (54.5) 32 202 131 (21) 113114.5) 95 (100)

a Alcohol derived from enyne in parenthesis. Loss of propionic acid instead of acetic acid.

I OR' I I

I I I I

I

I A

0 R'

1

I

I B I

1

OR'

OH

R = H or C K H j

A

ion or SHIFTED (with chemical scrambling)

* 2H* OR' EPOXIDIZED A -

H n 2

ion b or &' NOT SHIFTED

- *H2 EPOXIDIZED 6 -.--

Scheme 3. General methodology: enynes A and B can give rise to the same alcohol under the two-step derivatization: (1) m-CPBA/CH,CI,; (2) H,/PtO,/MeOH. Deuteration of the epoxidized enynes allows their differentiation.


b' ----.

Figure 3. El mass spectra of the *H-labelled alcohols derived from enynes 1. 8 and 9. (a) ('H) 18. (b) ('H) 24. (c) ('H) 25.

when a protonated aldehyde is susceptible of being formed it should easily lose water, thus exclude the existence of a b type ion in the decomposition of the molecular ion a (Scheme 2). Consequently, the a- cleavage, which occurs in hydroxy acetates under EI, is most probably produced uia a prior (or concerted) hydrogen transfer isomerization leading to a b' type ion. A similar long range hydrogen rearrangement in the molecular ion has been suggested by Wolff et ~ 1 , ~ ' to explain the EI fragmentation of long chain hydroxy methyl esters.

In the case of diols, EI mass spectra were more simply interpretable than those of the corresponding hydroxy acetates. For instance, diol25, whose EI mass spectrum can be compared to that of hydroxy acetate 24, shows a [M-C,H;,]+ ( m / z 173) ion produced by a-cleavage, which can then decompose by consecutive losses of water (ions at m / z 155 and 137). On the other hand, the peaks presumably formed by a'-cleavage (with or without O H rearrangement) from the molecular ion were absent or in too low abundances to be used in structural elucidation and, hence, the a-cleavage must be considered as the main decomposition pathway of [MI+'

Mass spectra of the deuterated alcohol derivatives

As shown above, the position of the secondary hydroxyl group is unambiguously defined by the diagnostic peaks [M-R']+, [M-R-AcOH]~, [M-R'-AcOH-HZO]+

and [M - RCHO - AcOH]+' for hydroxy acetates and [M-R]+, [M-R'-H,O]+ and [M-R-2H20]+ for diols (Table 4).

However, since the same alcohol could originate from two different enynes (A and B, Scheme 3), definite location of the enyne function can only be accomplished by comparison of the EI mass spectrum of the secondary alcohol, obtained by the standard procedure, with that resulting from deuteration of the intermediate epoxide.

Enyne-acetates 1 (type A) and 8 (type B) can serve as typical examples. When compound 1 was subjected to epoxidation followed by deuteration (*Hz/Me02H/Pt02) the EI spectrum of the resulting labelled hydroxy acetate (*H) 18 (Fig. 3(a)) showed a cluster of peaks at m / z 275-285, the most intense being at m / z 277. These ions correspond to the original [M - R']+ ion ( m / z 271) of 18. The difference of about 6 u (calculated 6.6) represents the mean number of 2H atoms introduced into the molecule between the hydroxyl and ester groups. This shift effect (with chemical scrambling) is also observed for each peak previously studied. On the other hand, for ('H) 24, the labelled hydroxy acetate from enyne 8, the diagnostic peaks (Fig. 3(b)) appeared differentiated and were not shifted. The appearance of a [ M - R + I]' ion at m / z 216 accom- panying the [M - R']+ ion ( m / z 215) is due to the deuterated hydroxyl group (O'H). In the corresponding diol ('H) 25, which may contain two O'H groups (Fig. 3( c)), twopeaksemergeat m / z 174[M-R+1]+and m / z 175 (M - R + 2]+ together with that expected at m / z 173 [M-R']+. All these ions can easily be shifted to the


LOCALIZATION OF DOUBLE A N D TRIPLE BONDS

Table 5. Relative abundances ("/o) of the [MZH + HIf and [MZH +NHJ ions in the CI NH, spectra of ('H)18 and (*H)24"

Ions [MzH +HI+

m l z 303 304 305 306 307 308 309 310 311 312 313 314

9 8 5 4 1

('H) 18 5 26 62 100 80 48 31 20 15 ('H) 24 5 22 52 100 57 51 31 17 13 8

~~ ~~

320 321 322 323 324 325 326 327 328 329 330 331

('H) 18 <1 4 8 17 15 8 4 3 2 3 1 <1 ('H) 24 2 6 24 55 37 26 20 11 6 4 3 1

a [M+HJ+ and [ M +NH,J+ ions for unlabelled 18 and 24 are respectivelv at m l z 301 and 318

[M - R]+ ion after treatment of the labelled crude prod- uct with water. Therefore, introduction of 'H atoms in ('H) 24, which occurs as in (*H) 18 with some chemical scrambling (cf. CI NH3 data, Table 5), presumably takes place on the non-functionalized side chain (Scheme 3).

CONCLUSION

structures ( A and B) may give rise to the same secondary alcohol, definite assignment is then possible by using 'H-labelling conditions in the derivatization sequence. The diagnostic peaks are shifted and appear as clusters when the initial enyne belongs to type A, whereas the pattern and rn/z values are practically unmodified for enynes of type B. The 'H-labelling derivatization may not be necessary if the enyne position is near the end of the chain (i.e. 1).

The localization of the enyne function in long chain conjugated enyne-acetates and alcohols can be effected through a two-step derivatization reaction. The standard

T h e authors are grateful to Dr S. Voerman (Institute for Pesticide procedure (epoxidation by hydro- Research, Wageningen, The Netherlands) for supplying a sample of genation) yields a secondary alcohol which can be iden- (~)-4-nonen-7-vn-l-v1 acetate and to Dr J. H. Tumlinson (USDA. . , -~ iified by EI GC/MS. However, since two possible enyne Gainesville, Florida, USA) for critically reading the manuscript.

REFERENCES

1. C. A. Henrick, Tetrahedron 33, 1845 (1977). 2. K. Mori, in Tbe Total Synthesis of Natural Products, Vol. IV,

edited by J. Apsimon, p. 1-185. Wiley-Interscience, New York (1981).

3. A. Guerrero, F. Camps, J. Coll, M. Riba, J. Einhorn, C. Descoins and J. Y. Lallemand, Tetrahedron Lett. 22, 2013 (1981).

4. B. A. Bierl-Leonhardt, E. D. DeVilbiss and J. R. Plimmer, J. Cbromatogr. Sci. 18, 364 (1980).

5. H. R. Buser, H. Am, P. Guerin and S. Rauscher, Anal. Cbem. 55, 818 (1983).

6. G. Janssen and G. Parmentier, Biomed. Mass Spectrom. 5,439 (1978) and references therein.

7. M. Beroza and B. A. Bierl, Anal. Chem. 39, 1131 (1967). 8. H. E. Audier, J. P. Begue, P. Cadiot and M. Fetizon, Chem.

9. F. Bohlmann and H. Sinn, Cbem. Ber. 88, 1869 (1955). Commun. 200 (1967).

10. R. J. Greathead and K. R. Jennings, Org. Mass. Spectrom. 15,

11. E. Busker and H. Budzikiewicz, Org. Mass. Spectrom. 14, 222

12. H. Budzikiewicz and E. Busker, Tetrahedron 36, 255 (1980). 13. G. F. Spencer, R. Kleiman, F. R. Earle and 1. A. Wolff, Anal.

431 (1980) and references therein.

(1979).

Chem. 41, 1874 (1969).

14. T. W. Shannon, T. E. Mead, C. G. Warner, F. W. McLafferty, Anal. Cbem. 39, 1748 (1967).

15. (a) J. H. Beynon, R. G. Cooks, J. W. Amy, W. E. Baitinger and T. J. Ridley, Anal. Cbem. 45, 1023 (1973). (b) U. P. Schlunegger, Angew. Cbem., lnt. Ed. fngl. 14,679 (1975). (c) J. H. Beynon and R. G. Cooks, in Mass Spectrom., lnternational Review of Science, edited by A. Macoll. Butterworth, London (1975).

16. (a) D. Samain, Doctoral thesis ('es-Sciences Physiques'), Paris VI (1978). (b) F. Camps, J. Coll, R. Canela, A. Guerrero and M. Riba, Chem. Lett. 703 (1981). (c) D. Michelot, A. Guerrero and V. Ratovelomanana, J. Chem. Res. (S) , 93 (1982).

17. J. H. Tumlinson, R. R. Heath and R. E. Doolittle, Anal. dhem. 46, 1309 (1974).

18. (a) M. Meot-ner (Mautner), J. Am. Chem. SOC. 101,2396 (1979). (b) M. Meot-ner (Mautner), J. Phys. Cbem. 84, 2716 (1980).

19. D. H. Aue, H. M. Weeb, M. T. Bowers, C. L. Liotta, C. J. Alexander and H. P. Hopkins, J. Am. Cbem. SOC. 38,854 (1976).

20. R. E. Wolff, M. Greff and J. A. McCloskey, Adv. Mass Spectrom. 4, 193 (1 968).

Received 2 August 1984; accepted (revised) 19 November 1984


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Localization of double and triple bonds in linear conjugated enyne-acetates and alcohols