Venom chemistry of the ant Myrmicaria melanogaster from Brunei

Article abstract of DOI:10.1021/np068034t

Analysis of the extracts of the ant Myrmicaria melanogaster from Brunei in the Indonesian archipelago by GC-MS and GC-IR revealed the presence of five new alkaloids, identified as (9Z)-3-propylindolizidine (1), cis- and trans-2-butyl-5-propylpyrrolidine (

Full text of DOI:10.1021/np068034t

160
J. Nat. Prod. 2007, 70, 160-168
Venom Chemistry of the Ant Myrmicaria melanogaster from Brunei
Tappey H. Jones,*,† Heather L. Voegtle,† Heather M. Miras,† Robert G. Weatherford,† Thomas F. Spande,‡ H. Martin Garraffo,‡
John W. Daly,‡ Diane W. Davidson,§ and Roy R. Snelling
Department of Chemistry, Virginia Military Institute, Lexington, Virginia 24450, Laboratory of Bioorganic Chemistry, NIDDK,
National Institutes of Health, HHS, Bethesda, Maryland 20892-0820, Department of Biology, UniVersity of Utah, 257 South, 1400 East,
Salt Lake City, Utah 84112-0840, and Los Angeles County Museum of Natural History, 900 Exposition BouleVard,
Los Angeles, California 90007
ReceiVed July 19, 2006
Analysis of the extracts of the ant Myrmicaria melanogaster from Brunei in the Indonesian archipelago by GC-MS and
GC-IR revealed the presence of five new alkaloids, identified as (9Z)-3-propylindolizidine (1), cis- and trans-2-butyl-
5-propylpyrrolidine (2 and 3, respectively), (10E)-3-butyllehmizidine (7), and (5Z,8Z,9Z)-3-butyl-5-propyl-8-hydroxy-
indolizidine (10a), whose structures were established by comparison with synthetic samples. In addition the monoterpene
hydrocarbons â-pinene, myrcene, and limonene were detected along with all four isomers of 3-butyl-5-methylindolizidine
(4a-d), cis- and trans-2-butyl-5-(4-pentenyl)pyrrolidine (5a and 5b), trans-2-butyl-5-pentylpyrrolidine (6), (5Z,9Z)-3-
butyl-5-propylindolizidine (8), and (5Z,9E)-3-butyl-5-propylindolizidine (9), alkaloids well known from ants and frogs,
whose structures were established on the basis of published spectra or comparison with authentic samples. This study
utilized vapor-phase infrared analysis for the assignment of stereochemistry using Bohlmann bands for the bicyclic
alkaloids and, in the case of 10a, the detection of an intramolecular hydrogen bond. A biogenetic relationship between
the mono- and bicyclic ring systems is proposed.
Ring-saturated nitrogen heterocycles are well-known components
of the venoms of ants in the subfamily Myrmicinae, particularly in
the genera Megalomyrmex, Monomorium, and Solenopsis.1-3 These
alkaloid structures are usually based on an unbranched carbon
skeleton cyclized with nitrogen to form monocyclic pyrrolidines
and piperidines, or bicyclic pyrrolizidines, indolizidines, quinoliz-
idines, and decahydroquinolines.4 In a number of species, the
bicyclic compounds are present with their monocyclic homologues.5-9
Monoterpene hydrocarbons have been reported in the poison glands
of myrmicine ants in the genus Myrmicaria from Africa for over
30 years;10 however, more recently indolizines reminiscent of the
Megalomyrmex, Monomorium, and Solenopsis alkaloids, as well
as complex polycyclic alkaloids, have been demonstrated from the
venom glands of several African species in this genus.11-14 In
Myrmicaria, a close relative of Megalomyrmex,15 the monoterpene
hydrocarbons have a role as recruitment pheromones, while the
alkaloids serve defensively.13 In this report we describe the
elucidation of the structures of three terpenes and nine bicyclic and
five homologous monocyclic alkaloids detected in Myrmicaria
melanogaster (Emery), a species reported only from Borneo and
collected in the sultanate of Brunei Darussalam. These ants nest
beneath leaves in the understory or subcanopy and travel to the
canopy to tend homoptera (order Hemiptera). The venom gland
contents are sprayed at enemies met head-on with the gaster doubled
ventrally and its tip aimed forward. Eight of the 14 alkaloids from
M. melanogaster have been reported from frog skin extracts.16
alkaloids (Figure 2) were easily recognizable by the presence of
abundant, even-mass fragment ions in their electron-impact mass
spectra (EIMS). Authentic samples of a number of them were
available from previous work. The four isomers of 3-butyl-5-
methylindolizidine (4a-d) were identified by their retention times
and EIMS and gas chromatography-Fourier-transform infrared
spectra (GC-FTIR spectra), which were identical with those of
authentic samples.17 All four isomers have been detected in frog
skin extracts.18 The EIMS of the major components 5b and 6
suggested 2-butylpyrrolidines with a five-carbon chain at C-5.
Additionally, 5b showed infrared absorption bands at 913, 993,
1641, and 3084 cm-1, indicating the presence of a -CHdCH2
group,19 and was converted to 6 upon catalytic hydrogenation.
Comparison with authentic samples showed 5a and 5b to be the
cis and trans isomers of 2-butyl-5-(4-pentenyl)pyrrolidine, respec-
tively,20 and 6 to be trans-2-butyl-5-pentylpyrrolidine.21 Pyrrolidine
6 is well known from ants1 and has been detected in frog skin
extracts and referred to as alkaloid 197B.18 The EIMS and GC-
FTIR data of 8 and 9 (ca. 20:1) were identical to those published
for (5Z,9Z)-3-butyl-5-propylindolizidine and (5Z,9E)-3-butyl-5-
propylindolizidine, respectively.18 Two diastereomers were found
in Solenopis (Diplorhoptrum) ants of Puerto Rico, the 5Z,9Z and
5E,9E isomers in significantly different ratios in the three popula-
tions sampled.9 The 5E,9E diastereomer was originally discovered
in the dendrobatid frog Oophaga silVatica (formerly Dendrobates
histrionicus), collected in Narin˜o, Colombia.22 The 5Z,9Z dia-
stereomer (8) was then found in Oophaga speciosus (formerly
Dendrobates speciosus), from Chiriqu´ı, Panama,23 and all four
diastereomers were found in extracts of the Argentinian bufonid
toad Melanophryniscus stelzneri.18 All isomers are referred to as
alkaloid 223AB. The remaining alkaloids, 1-3, 7, and 10, were
unchanged by hydrogenation, and their structures were suggested
by their EIMS and GC-FTIR spectra, but required syntheses to
confirm. None of these have been detected previously from either
ant or frog skin extracts.
Results and Discussion
The initial gas chromatography-mass spectrometry (GC-MS)
analysis of MeOH extracts of whole M. melanogaster collected in
Brunei revealed the presence of three monoterpene hydrocarbons,
â-pinene, myrcene, and limonene (peaks A, B, C) and 14 alkaloids
(1-10) (Figure 1). The terpenes were identified from their mass
spectra and by direct comparison with authentic samples. The
* To whom correspondence should be addressed. Tel: (540)-464-7422.
Fax: (540)-464-7261. E-mail: jonesth@vmi.edu.
† Virginia Military Institute.
The EIMS of the 11-carbon alkaloids, 1-3, all showed intense
ions for the loss of propyl. In the case of 1, the EIMS showed a
molecular ion at m/z 167 and an intense ion at m/z 124 indicating
a bicyclic structure and supporting the loss of a propyl group from
the carbon next to nitrogen (R-cleavage). A (5Z,9Z)-5-propyl-
‡ NIDDK, NIH.
§ University of Utah.
Los Angeles County Museum of Natural History.
10.1021/np068034t CCC: $37.00
© 2007 American Chemical Society and American Society of Pharmacognosy
Published on Web 01/23/2007

Venom Chemistry of the Ant Myrmicaria melanogaster
Journal of Natural Products, 2007, Vol. 70, No. 2 161
Figure 1. Total ion GC chromatogram of the venom gland extracts of the ant Myrmicaria melanogaster from Brunei. GC peaks A-C are
terpenes, while GC peaks numbered 1-10 are alkaloids whose structure and synthesis are discussed in the text.
Scheme 1. Synthesis of Racemic (3,9Z)-(1) and
(3,9E)-3-Propylindolizidine and Racemic cis and trans Isomers
of 2-Propyl-5-butylpyrrolidines (2 and 3, respectively)a
a
One enantiomer of the alkaloids 1-3 (relative configuration is shown) is
presumed to be naturally occurring in the ant Myrmicaria melanogaster from
Brunei (see text).
or storage due to its volatility. The structure for alkaloid 167B
proposed in 198226 was based only upon GC-EIMS and by analogy
with other indolizidines in which odd-numbered side-chains were
found invariably in the six-membered ring. Consequently, the
natural occurrence of 5-propylindolizidine, referred to as alkaloid
167B, should it be detected again, would require more rigorous
Figure 2. Alkaloids found in the ant venom extracts of Myrmicaria
melanogaster workers from Brunei. See Figure 1 for the relative
amounts. Only relative configurations are known. The occurrence
proof, now available from GC-FTIR and CI-MS/MS spectra (see
of only one enantiomer is assumed.
below). However, direct comparison showed 1 was not identical
to an authentic sample of either of the two diastereomers of
indolizidine was originally reported as trace alkaloid 167B in three
dendrobatid frog extracts and has been synthesized by a number
of groups (including our own, using the synthesis of ref 24). Shortly
after original comparison work with synthetic material supplied by
Holmes et al.,25 alkaloid 167B could no longer be detected in any
of the frog skin extracts; it was presumably lost during handling
5-propylindolizidine.24 The desired two 3-propylindolizidine isomers
were prepared from picoline in a straightforward manner (Scheme
1), and direct comparison of GC-EIMS, GC-retention times, and
GC-FTIR spectra proved that 1 was identical to the first eluting
propylindolizidine and had the broader, significant Bohlmann band
pattern typical of the 3,9-Z configuration (see Figure 3) where the

162 Journal of Natural Products, 2007, Vol. 70, No. 2
Jones et al.
Figure 3. Vapor-phase FTIR spectra of the monosubstituted indolizidines and lehmizidines. The 3-substituted indolizidine 1 and lehmizidine
7 occur naturally in the venom of workers of the ant Myrmicaria melanogaster from Brunei (see text). Only relative configurations are
depicted.
three CHN hydrogens are trans antiparallel to the nitrogen lone
pair.27 In Figure 3 are shown FTIR spectra of the two diastereomers
of 3- and 5-propylindolizidine. It will be noted that the Bohlmann
band pattern (νCH 2800-2600 cm-1) of the 5,9-Z isomer of the
5-substituted indolizidine is enhanced relative to the 3,9-Z isomer
of the 3-substituted indolizidine.
The application of a less commonly used mass spectrometric
technique, that of chemical ionization with tandem mass spectrom-
etry (CI-MS/MS), was extended here to monosubstituted “izidines”.
CI-MS/MS with ammonia reagent gas has proven extremely useful
in determining the gross structures of “izidines” with an N-CH(R)-
in each ring.28 Here, however, rather than seeing the expected ions
reflecting a ring and the particular ring substituent, only the ion
corresponding to the unsubstituted ring was observed; the corre-
sponding ion for the substituted ring was not apparent. This is not
quite so useful as in the disubstituted “izidine” cases, but still
indicates indirectly which ring is substituted. The 3- and 5-propyl
indolizidines, for example, showed ions at m/z 84 and 70,
respectively, demonstrating that a six-membered ring is unsubsti-
tuted in both of the 3-propylindolizidines and that the five-
membered ring lacks a substituent in both the 5-propylindolizidines.
By way of rationalization of this fragmentation, it is possible that
the more substituted neutral fragment is preferentially extruded in
analogy with the expected loss under EIMS conditions of the more
substituted radical.
Alkaloids 2 and 3 appeared to be isomeric pyrrolidines of
molecular weight 169, with the intense ions at m/z 126 and 112
indicating loss of propyl and butyl groups. Both isomers of 2-butyl-
5-propyl pyrrolidine were easily prepared (Scheme 1) by reductive
amination of 4,7-undecadione (12) and were identical to 2 and 3
by direct GC comparison, with the cis isomer eluting first, as is
invariably the case with pyrrolidines.21

Venom Chemistry of the Ant Myrmicaria melanogaster
Journal of Natural Products, 2007, Vol. 70, No. 2 163
Scheme 2. Synthesis of Racemic (3,10Z)- and
(3,10E)-3-Butyllehmizidinea
Scheme 3. Synthesis of the Four Racemic Diastereomers
(10a-d) of 3-Butyl-5-propyl-8-hydroxyindolizidinea
a
Diastereomer 7 is naturally occurring in the ant Myrmicaria melanogaster
from Brunei (see text).
Alkaloid 7, isomeric with the 3-butyl-5-methylindolizidines 4a-
d, has not been described previously. The EIMS of 7 showed a
molecular ion at m/z 195 and a base peak at m/z 138 (M - C4H9),
reminiscent of the mass spectra of the 3-butyl-5-methylindolizidines,
but without the weak ion at m/z 180 (M - CH3). The presence of
a pyrrolidine ring and a butyl group in alkaloids 4-6 suggested
that 7 might be a 3-butyl-5H-octahydropyrrolo[1,2-a]azepine, whose
trivial name would be 3-butyllehmizidine.29 A number of lehmiz-
idines with a methyl in the seven-membered ring and a nine-carbon
moiety in the five-membered ring have been reported in frog skin
extracts,29 but none with only a single substituent in the five-
membered ring. Both isomers of 3-butyllehmizidine were prepared
(Scheme 2), and the GC retention time and EIMS and FTIR spectra
of 7 (see Figure 3) were identical to those of the second eluting
synthetic butyllehmizidine. On the basis of the weaker Bohlmann
band in the FTIR spectrum, this isomer was assigned the 3,10E
configuration. The CI-MS/MS technique described above yielded
an ion at m/z 98 for both diastereomers, indicating that an
unsubstituted seven-membered ring was present.
Alkaloid 10a, of nominal molecular weight 239, possesses a
molecular formula of C15H29NO (high-resolution MS, HRMS), and
the EIMS had intense ions at m/z 196 and 182, indicating the loss
of propyl and butyl units, respectively. Additionally, the GC-FTIR
spectrum suggested an all-cis-substituted (i.e., 5Z,9Z) indolizidine
and showed an absorption at 3528 cm-1, indicating an intra-
molecularly hydrogen-bonded hydroxyl group. As reference com-
pounds, we hydrogenated the exo-alkylidene moiety of a small
sample of pumiliotoxin 251D, an indolizidine possessing an axial
hydroxyl group at C-8 that shows hydrogen bonding to nitrogen.
The reduction mixture showed on GC-FTIR a νOH of 3547 cm-1
for the major diastereomer (3 parts) and 3535 cm-1 for the minor
diastereomer (1 part), supporting our suspicion that the axial
hydroxyl of 10a was at the 8-position, a conclusion further
strengthened by the EI mass spectral fragmentation for 10a and
10b shown in Scheme 5.
The orientation of the hydroxyl group in alkaloid 10a is likely
axial at C-8 in a trans-fused indolizidine, which is the stereochem-
istry that is accessible by the elegant indolizidine synthesis of
Jefford et al.30 We used the Jefford methodology as an outline, but
incorporated the butyl group from the start of the synthesis in our
route to the 8-hydroxyindolizidines (Scheme 3). The intramolecular
acylation of pyrrole ester 15 using BBr3 formed the dihydro-8-
indolizone (16) nearly quantitatively. Jefford’s work described the
stereospecific hydrogenation of a similar compound, which, how-
ever, was unsubstituted at C-3, using a rhodium-on-alumina catalyst
in ethanol with a trace of acetic acid.30 With the 3-butyl group
present in 16, we observed complete loss of the hydroxyl group by
hydrogenolysis during the Jefford procedure, but when the reaction
was carried out in ethyl acetate containing a trace of the base,
triethylamine, four isomers, 10a, 10b, 10c, and 10d, were formed
as the major products in a 3:1:6:4.7 ratio and hydrogenolysis was
largely but not completely eliminated since 10a-d were still
a Diastereomer 10a (see Scheme 4) is naturally occurring in the ant
Myrmicaria melanogaster from Brunei (see text).
accompanied by very small amounts of (5Z,9Z)- and (5E,9Z)-223AB
and a totally unexpected third 223AB diastereomer, with the 5E,9E
stereochemistry. These minor side reactions evidently arise from
hydrogenolysis ensuing when the keto group is reduced to an
alcohol before the pyrrole moiety. Identifications were made by
GC retention times, characteristic EIMS, and comparison to
reference GC-FTIR spectra of the 223AB diastereomers.18 A small
amount of starting material 16 and the 7,8-dehydro transformation
product of 16 were also detected. The Bohlmann band patterns of
the reference GC-FTIR spectra allowed the assignment of the
relative stereochemistries of 10a-d. Diastereomers 10a and 10b
both possessed a hydrogen-bonded axial hydroxyl group with νOH
of 3528 and 3539 cm-1, respectively.19 On the basis of their
Bohlmann band patterns we have assigned them 5Z,8Z,9Z and
5E,8Z,9Z configurations, respectively. Diastereomers 10c and 10d
possessed non-hydrogen-bonded equatorial hydroxyl groups with
νOH of 3653 and 3649 cm-1 and νC-O of 1063 and 1055 cm-1
,
respectively. The strong νC-O is typical of an equatorial C-O
stretching frequency19 and is not seen with the axial hydroxyl groups
of 10a and 10b. The Bohlmann band patterns were closely matched
with those of the 223AB diastereomers of the 5E,9Z and 5Z,9E
configurations; consequently we assigned the 5E,8E,9Z and 5Z,8E,9E
configurations to 10c and 10d, respectively (Figure 4). Scheme 4
is a proposed mechanism for the formation of these four hydroxy-
indolizidines. Three have the 3- and 9-hydrogens on the same face,
as expected for a concerted reduction of the pyrrole ring. These
results are rationalized by assuming initial reduction of the pyrrole
moiety of 16 followed by reduction of the 8-keto group with
significant stereocontrol provided by the 5-propyl group. The
diastereomer 10d, with the 3- and 9-hydrogen on opposite faces,
is proposed to result from a 1,6-addition of hydrogen and keton-
ization to give an axial-transfer of hydrogen, then a final reduction
of the intermediate. This stereochemical result was totally unex-
pected, as was the absence of the 8E (equatorial) hydroxyl epimer
of 10a. Evidently the steric bulk of the two R-C-3 and C-5
substituents must block hydrogenation of the 8-ketone from the
R-face.
It was noted that the two H-bonded diastereomers, 10a and 10b,
show a characteristic m/z 154 ion (10%) in the EIMS that is lacking
in the non-hydrogen-bonded diastereomers, 10c and 10d. We
propose the fragmentation pathway shown in Scheme 5, whereby
a hexyl radical is extruded as a result of the transfer of a hydrogen
radical from the 8R-hydroxyl group to the nitrogen radical ion. That
concerted mechanism would be possible only with the axial
8-hydroxyl group and may provide the driving force for this

164 Journal of Natural Products, 2007, Vol. 70, No. 2
Jones et al.
Scheme 4. Suggested Pathways for Formation of Racemic Diastereomers (10a-d) from Hydrogenation of Pyrrole Intermediate 16a
a Only relative configurations are shown.
Scheme 5. Proposal for the Formation of the m/z 154 Ion in the EIMS of 10a and 10b and of the m/z 152 Ion in the CI-MS/MS of
10a-da
a The m/z 154 ion is diagnostic for the 8-axial hydroxyl group and is seen only with 10a and 10b. The m/z 152 ion is seen for all the 8-hydroxyindolizidines 10a-d
(see text).
fragmentation. All four diastereomers 10a-d have similar frag-
mentation patterns in the CI-MS/MS. CI-MS/MS on the deu-
teronated 10a-d led to a loss of D2O via the proposed deuterium-
free ion (m/z 222, 100%) that then gives a retro-Diels-Alder type
cleavage to the m/z 152 ion as the base peak in a third stage of
CI-MS/MS.
required, so as to obtain all possible diastereomers, for comparison
purposes with the natural materials. In addition, racemic materials
were desired as we plan chiral GC experiments in the future to
determine whether the absolute stereochemistries of ant and frog
alkaloids are the same, and in initial work we first need to show
that enantiomers can be separated.
A ring-hydroxylated indolizidine, alkaloid 239X, with the
hydroxyl group not hydrogen-bonded (νO-H 3652 cm-1) has been
discovered in a dendrobatid frog, but is not identical to any of 10a-
10d. A gross structure for 239X has been proposed,16 but further
analysis is required.
In terms of the known frog skin alkaloids, many of which
derive from dietary ants, we observe here two new variations of
known frog skin alkaloids: the 3-monosubstituted-indolizidine and
-lehmizidine, which have substitution patterns yet undetected
in frog skin. The known lehmizidines, all of which are disub-
sitituted, have so far been reported only in Oophags lehmanni
(formerly Dendrobates lehmanni) from Colombia. Extensive studies
on Madagascan frogs in the endemic genus Mantella have not
yielded “izidines” with a substituent only in the five-membered
ring.
All of the previous investigations of ants in the genus Myrmicaria
have shown the presence of well-known monoterpene hydrocarbons
in their venom glands, and while alkaloids were not detected in
the South African species M. natalensis,10 indolizidine ketones and
more complex tri- and polycyclic alkaloids have been found in other
African species collected in Kenya.11-14 These alkaloids, reminis-
cent of the venom alkaloids found in Monomorium and Solenopsis
species, are indolizines containing an unbranched carbon-chain
cyclized to nitrogen, with the more complex compounds being based
on a set of two or three condensed C15 indolizines. In contrast,
M. melanogaster from Brunei contains a mixture of C11, C13, and
It should be noted that, while IR spectroscopy is being used
considerably less frequently in characterization work on unknowns
than a few decades ago, we have found that gas chromatography-
vapor-phase IR spectroscopic analysis at the sub-microgram level
is capable of quickly assigning essential structural details for ant
and frog alkaloids where amounts and the need for purification
remain significant barriers for even the present, very sensitive NMR
techniques. The limited amounts and complex mixture of the
alkaloids present in the Brunei ant extract precluded any attempt
1
at isolation and H NMR spectroscopy. In many cases, EI and CI
mass spectrometric fragmentations, combined with study of FTIR
Bohlmann band patterns, allow the preliminary assignment of ring
systems and their stereochemistry. At this point, synthesis is
undertaken to provide rigorous confirmation by spectroscopic
comparisons and GC retention times with coinjections. For the
synthetic work of this study, nonstereospecific syntheses were

Venom Chemistry of the Ant Myrmicaria melanogaster
Journal of Natural Products, 2007, Vol. 70, No. 2 165
Figure 4. Vapor-phase GC-FTIR spectra of the four synthetic diastereomers 10a-d of 3-butyl-5-propyl-8-hydroxyindolizidine. Diastereomer
10a is found in the venom of the ant Myrmicaria melanogaster from Brunei (see text). Only relative configurations are depicted.
C15 alkaloids with homologous bi- and monocyclic compounds
present, some of which have been previously reported from
Monomorium and Solenopsis species. Recent work in phylogenetic
systematics15 places these two genera in the sister clade to the clade
containing Myrmicaria and Megalomyrmex.
These results contrast with Monomorium pharaonis, where the
(5Z,9Z)-4a with a cis-substituted pyrrolidine ring occurs together
with the trans-substituted 5b.5,6 While other isomers of 3-alkyl-5-
methylindolizidines have been found along with their homologous
piperidines in Solenopsis (Diplorhoptrum) species, M. melanogaster
exhibits the first occurrence of a 5E,9Z isomer, 4b, containing an
axial 5-methyl group.31
The presence of concomitant homologous bi- and monocyclic
alkaloids, 4a and 5b, in an ant venom was first reported in
Monomorium pharaonis in 1975.5 This finding in other myrmicine
species has suggested that the ring-type, regio- and diastereoisomer
of the monocyclic compound might have been formed first,
followed by formation of the bicyclic compound, or at least that
these compounds had a common biosynthetic precursor.6-9,31 In
some cases, the stereochemistry of the monocyclic alkaloid is
opposite that of the corresponding ring in the homologous bicyclic
alkaloid.5,7,8 In M. melanogaster, however, concomitance with
identical stereochemistry is present in the C11 and C13 alkaloids,
where 3-propylindolizidine 1 represents a cyclized form of the
pyrrolidine 2, and 3-butyllehmizidine 7 represents a cyclized form
of 5b or 6. Surprisingly we did not detect the 2-(3-butenyl) analogue
of 5b, a putative precursor of 1 and 2. Additionally, 1 and 7 are
the first examples of monosubstituted bicyclic alkaloids from ants
apparently resulting from cyclization at the terminal carbon of one
of the pyrrolidine side-chains. On the other hand, 4a-d can be
seen as resulting from cyclization at the penultimate carbon of the
C5 chain of 5b or 6. Interestingly, all the bicyclic alkaloids reported
here, 1, 4a-d, 7-9, and 10a-d, can be seen as derived from
appropriately 5-substituted 2-butylpyrrolidines. The ring stereo-
chemistry of 1 and 7 also reflects that of the corresponding
pyrrolidines. (3,9Z)-3-Propylindolizidine (1) has the cis-substituted
pyrrolidine ring of 2, and (3,10E)-3-butyllehmizidine (7) has the
trans-substituted pyrrolidine ring of 5b or 6. In contrast, the four
isomers of 4 would derive from both cis- and trans-pyrrolidines.
Myrmicine venom alkaloids having an oxygen function are quite
rare, and the few that have been reported have side-chain ketones
and occur in Myrmicaria species.11-13 Although isoprene-derived
pyrrolidines containing side-chain alcohol groups have been
reported in the ant Harpagoxenus sublaeVis,32 the presence of 10a
in M. melanogaster is the first reported ring-hydroxylated, acetate-
derived ant venom alkaloid. Additionally, since the stereochemistry
of 10a is the same as that of 8, the major 223AB isomer present in
M. melanogaster, its presence may be indicative of the biosynthetic
pathway to indolizidines in this species. Among all the known ant
venom alkaloids, the polyacetate pathway has been established by
labeling studies only for the 2-alkyl-6-methylpiperidines from
Solenopsis spp., in which case the oxygen functionality in the ring
would be at the 4-position relative to the nitrogen.33 Piperidines or
pyrrolidines have been found in ants as concomitants of 3,5-
dialkylindolizidines,5-9,31 and in previous work, it has been sug-
gested on the basis of stereochemical considerations that the first
formed ring of ant-derived indolizidines is the same as in their
monocyclic concomitants.6 Along with a 2-butylpyrrolidine moiety
in all of the alkaloids in M. melanogaster, the C-8-OH of 10a
strengthens that perception, since the hydroxyl would be at C-7 if
the six-membered ring were formed first by the polyacetate
pathway. Although it has been proposed that the six-membered ring
is formed first in other Myrmicaria alkaloids, no monocyclic
concomitants are reported in those cases.13

166 Journal of Natural Products, 2007, Vol. 70, No. 2
Jones et al.
Experimental Section
4,7-Undecadione (12). A mixture of 0.45 g of butanal (6.25 mmol),
0.70 g of 1-heptene-3-one (6.25 mmol), and 0.2 g of 5-(2-hydroxyethyl)-
4-methyl-3-benzylthiazolium chloride was treated with 2 mL of
triethylamine and refluxed overnight under an argon atmosphere. The
usual workup21 provided 0.98 g (85% yield) of 12 that was 80%
homogeneous by GC-MS. EIMS m/z 184 [M+] (1), 142 (23), 127 (18),
113 (2), 99 (13), 85 (43), 71 (60), 57 (50), 55 (10), 43 (100), 41 (53);
HRMS m/z 185.1554 ([M + H]+), calcd for C11H21O2, 185.1542.
cis- and trans-2-Butyl-5-propylpyrrolidine (2 and 3). A solution
containing 0.5 g (2.7 mmol) of 12, 0.22 g of NH4OAc, and 0.17 g (2.7
mmol) of NaCNBH3 in 10 mL of methanol was stirred overnight and
worked up in the usual manner33 to provide 0.35 g (77% yield) of a
1:1 mixture of the pyrrolidines 2 and 3, whose GC retention times were
11.88 and 11.98 min, respectively, and which exhibited identical mass
spectra. EIMS m/z 169 [M+] (1), 169 (2), 140 (2), 127 (4), 126 (63),
113 (5), 112 (100), 98 (10), 95 (11), 82 (12), 70 (12), 69 (20), 56 (20),
55 (24), 44 (30), 41 (60); HRMS for both (direct probe) m/z 170.1918
([M + H]+), calcd for C11H24N, 170.1909. The GC-MS data for 2 and
3 were identical to those of the natural compounds.
General Experimental Procedures. GC-MS was carried out in the
EI mode using a Shimadzu QP-5000 GC-MS equipped with an RTX-
5, 30 m × 0.25 mm i.d. column. The instrument was programmed from
60 to 250 °C at 10 deg/min. Vapor-phase FT-IR spectra were obtained
using a Hewlett-Packard model 5965B detector interfaced with a
Hewlett-Packard 5890 gas chromatograph fitted with a 30 m × 0.25
mm RTX-5 amine column. NMR spectroscopy was carried out in CDCl3
solutions using a Varian Mercury 400 NMR spectrometer. HRMS was
performed on a JEOL SX102 instrument in the positive-ion fast-atom
bombardment mode using a direct probe and a Waters LCT Premier
time-of-flight instrument in the electrospray (ESI) mode. The mono-
terpenes were suggested from their mass spectra (NIST/EPA/NIH, 1999)
and retention times and confirmed by comparison with commercial
authentic samples.
Ants. Nine collections of Myrmicaria melanogaster (Emery) were
made over a 4-year period (2001-2005) at various times of the year
from two nests at the Kuala Belalong Field Studies Center, run by the
Universiti Brunei Darussalem and located in the Batu Apoi Forest
Reserve, Temburong District, Brunei, 4°32′ N, 115°10′ E. The workers
were placed in vials containing a small amount of methanol for analysis.
Voucher specimens have been deposited in the entomological collec-
tions of both the Brunei Museum and the Los Angeles County Natural
History Museum.
The ion chromatograms of the methanol extracts were consistent
for all of the extracts over the 5 years of collection. A GC-mass
chromatogram of one such extract is shown in Figure 1. The mass
spectra and retention times of peaks A, B, and C were identical to
those of â-pinene, myrcene, and limonene, respectively. The mass
spectra of peaks 1-10a all showed fragmentations that suggested their
structures. The FTIR spectra of peaks 5a and 5b showed an absorption
band at νmax 914 cm-1. When a stream of hydrogen was passed through
a few drops of the mixture in the presence of PtO2, 5 was converted to
6. The mass spectra and gas chromatographic retention times of peaks
4a-d, 5a, 5b, and 6 were identical to those of authentic samples. The
mass spectra and FTIR spectra of peaks 8 and 9 were identical to those
previously published.18 The structures of the remaining alkaloids were
established by direct comparison with synthetic samples.
2-[2-(1,3-Dioxolan-2-yl)ethyl]piperidine (11). 2-Picoline (4.0 g, 43
mmol) was added dropwise to 25 mL of 1.6 M butyllithium in 50 mL
of ether at 0 °C. After 0.5 h, 4.70 mL (40 mmol) of 2-(2-bromoethyl)-
1,3-dioxolane was added dropwise. The resulting mixture was allowed
to warm to ambient temperature and, after 0.5 h, carefully treated with
20 mL of H2O. The organic layer was separated, dried over anhydrous
K2CO3, and filtered and, after Kugelrohr distillation, provided 4.3 g
(56% yield) of 2-[2-(1,3-dioxolan-2-yl)ethyl]pyridine, EIMS m/z 178
[M - 1+] (1), 136 (5), 118 (10), 107 (15), 106 (25), 93 (47), 87 (17),
73 (100), 45 (62). A solution containing 1.0 g of this product in 50
mL of absolute ethanol containing 0.1 g of K2CO3 and 280 mg of 5%
Rh on Al2O3 was shaken under 3 atm H2 overnight. After filtration
through Celite, Kugelrohr distillation provided 0.6 g (60% yield) of
N-Benzyl-2-[2-(1,3-dioxan-2-yl)ethyl]azepane (13). A solution
containing 2.0 g (10 mmol) of N-benzylcaprolactam35 in 20 mL of THF
was cooled to 0 °C and treated with a 3-fold excess of the Grignard
reagent prepared from 2-(2-bromoethyl)-1,3-dioxane36 and stirred
overnight at room temperature. The mixture was cooled to 0 °C, and
1.24 g of NaCNBH3 was added followed by 8 mL of acetic acid. The
literature-described workup,37 followed by Kugelrohr distillation at
150-160 °C (0.15 mmHg), provided 1.5 g of 13 that was 81% pure
1
by GC analysis. H NMR (400 MHz, CDCl3) δ 7.29 (5H, m), 4.48
(1H, t, J ) 5.2 Hz), 4.09 (2H, dd, J ) 11.6 and 5 Hz), 3.75 (4H, m),
2.78 (2H, m), 2.60 (1H, m), 2.07 (1H, m), 1.8-1.4 (13H, brm); 13C
NMR (100 MHz, CDCl3) δ 141.43, 128.86 (2C), 128.31(2C), 126.72,
102.99, 67.16 (2C), 62.30, 55.30, 49.58, 33.54, 32.92, 28.67, 28.55,
27.34, 26.14, 25.98; EIMS m/z 303 [M+] (1), 302 (1), 216 (2), 189
(10), 188 (100), 160 (2), 96(3), 91 (93); HRMS m/z 304.2275 ([M +
1]+), calcd for C19H30NO2, 304.2277.
(3,10E)- and (3,10Z)-3-Butyllehmizidine (7). A 0.50 g (1.65 mmol)
sample of azepane 13 in 50 mL of methanol was refluxed overnight
with 1.0 g of ammonium formate and 1.0 g of 10% Pd/C. The usual
workup29 provided 0.35 g (70% yield) of 2-[2-(1,3-dioxan-2-yl)ethyl]-
azepane. EIMS m/z 213 [M+] (1), 212 (1), 170 (1), 154 (1), 138 (3),
99 (5), 98 (100), 87 (6), 70 (16), 69 (14), 56 (10), 41 (25). The crude
azepane acetal was stirred for 3 days in 10 mL of THF containing 5
mL of 10% HCl (v/v) and one drop of 70% HClO4 (v/v), then as
described for the cyclization of 11, treated sequentially with KCN and
an excess of n-butylmagnesium bromide. The usual workup provided
a 1:1 mixture of the isomers of 7. GC-FTIR νmax 2934, 2871, 2799,
1457, 1353, 1151 cm-1 and 2932, 2867, 1457, 1353 cm-1 for the first
and second eluting peaks, respectively. The GC-FTIR spectra for the
isomers of 7 are shown in Figure 3. EIMS m/z 195 [M+] (1), 166 (1),
152 (1), 139 (5). 138 (100), 136 (3), 110 (5), 96 (2), 82 (4), 68 (5), 55
(12), 41 (25); HRMS m/z 195.2005 ([M]+), calcd for C13H25N,
195.1987, 138.1283 ([M - C4H9]+), calcd for C9H16N, 138.1283. The
GC-MS and GC-FTIR data for the second eluting isomer were identical
to those of the natural 7.
1
11, bp 87-90 °C/0.27 mmHg; H NMR (400 MHz, CDCl3) δ 4.75
(1H, t, J ) 6 Hz), 3.86 (2H, m), 3.75 (2H, m), 2.96 (1H, d, J ) 12
Hz), 2.52 (1H, t, J ) 12 Hz), 2.37 (1H, m), 1.68-0.96 (11H, complex
m); 13C NMR (100 MHz, CDCl3) δ 104.8, 65.06, 65.02, 56.88, 47.41,
33.08, 31.79, 30.54, 26.82, 25.06; EIMS m/z 184 [M - 1+] (1), 113
(3), 85 (6), 84 (100), 73 (13), 56 (15); HRMS m/z 186.1509 ([M +
H]+), calcd for C10H20NO2, 186.1494.
4-Oxooctanal dimethyl Acetal (14). A solution containing 10.2 g
(100 mmol) of acrolein dimethyl acetal and 1.5 g of 2,2-azobisiso-
butyronitrile (AIBN) in 32 mL (300 mmol) of n-pentanal was heated
at 80 °C for 36 h. Fractional distillation of the mixture provided 7.0 g
(37% yield) of 14, bp 69-74 °C (0.55 mmHg). GC-FTIR νmax 2945,
(3,9E) and (3,9Z)-3-Propylindolizidine (1). A solution containing
0.50 g (2.7 mmol) of 11 in 10 mL of 10% HCl (v/v) was stirred for
1.0 h. After the addition of 20 mL of CH2Cl2, the mixture was carefully
brought to a methyl orange end point with KCN and stirred overnight.
The mixture was then made basic with a slight excess of KCN, and
the organic layer was separated and dried over K2CO3. The solvent
was removed in vacuo, and the residue was taken up in 10 mL of THF
and treated with an excess of n-propylmagnesium bromide to provide,
after the usual workup,4 0.4 g (90% yield) of a 1:1 mixture of 3,9Z-
and 3,9E-1. The GC-FTIR spectra for 3,9Z- and 3,9E-1 are shown in
Figure 3. GC-FTIR νmax 2941, 2872, 2783, 1455, 1370, 1265, 1197,
1123, and 1066 cm-1 and 2938, 2877, 2795, 1456, 1352 cm-1, respec-
tively; EIMS m/z 167 [M+] (1), 166 (2), 125 (10), 124 (100), 122 (4),
110 (2), 96 (2); HRMS for both (direct probe) m/z 168.1770 ([M +
H]+), calcd for C11H22N, 168.1752. The GC-MS and GC-FTIR data
for the first eluting isomer were identical to those of the natural 1.
2840, 1726 (s), 1448, 1364, 1192, 1125 (s), 1087 (s) cm-1 13C NMR
;
(100 MHz, CDCl3) δ 210.87, 104.05, 53.39 (2C), 42.85, 37.46, 29.74,
26.18, 22.55, 14.06; EIMS m/z 188 [M+] (0.5), 187 (1), 157 (15), 114
(9), 99 (5), 88 (25), 75 (100), 71 (30), 57 (20), 41 (33); HRMS m/z
157.1268 ([M - OCH3]+), calcd for C9H17O2, 157.1229; HR-CIMS
(negative ion) 187.1310 (M - H+)-, calcd for C10H13O3, 187.1334.
Ethyl-4-[N-2-butylpyrrolyl]heptanoate (15). A solution containing
3.2 g (18 mmol) of ethyl 4-oxoheptanoate,38 2.0 g (29 mmol) of
hydroxylamine hydrochloride, and 2 mL of pyridine in 25 mL of EtOH
was stirred overnight. After removal of the solvent in vacuo, the residue
was partitioned between ether and water, and the organic layer provided
2.6 g of the corresponding oxime after the removal of solvent. EIMS
m/z 187 [M+] (1), 170 (18), 159 (2), 142 (58), 141 (15), 126 (50), 124
(25), 114 (32), 113 (38), 100 (5), 98 (7), 96 (16), 82 (16), 70 (9), 69
(9), 68 (10),55 (32), 54 (38), 43 (63), 41 (100). The crude oxime was
taken up in 100 mL of EtOH containing 5 mL of CHCl3 and

Venom Chemistry of the Ant Myrmicaria melanogaster
Journal of Natural Products, 2007, Vol. 70, No. 2 167
hydrogenated at 3 atm over 0.35 g of PtO2 overnight.39 After filtration,
removal of the solvent in vacuo provided 2.8 g (75% yield) of the
ethyl 4-aminoheptanoate hydrochloride. EIMS (unstable free base) m/z
173 [M+] (0.1), 130 (29), 128 (7), 84 (89), 72 (100), 56 (36), 43 (17),
41 (38).
Additionally, small amounts of three isomers of alkaloid 223AB were
formed and identified by comparison with their literature GC-FTIR
and mass spectra.
Acknowledgment. T.H.J and H.L.V gratefully acknowledge the
support of the Camille and Henry Dreyfus Foundation, and D.W.D
thanks the NSF (IBN-9707932) and the University of Utah Research
Committee for travel funds. We thank Dr. J. Lloyd, NIDDK, for the
direct probe HRESIMS mass measurements reported in the Experi-
mental Section. The research done at NIH was supported by the
intramural research funds of NIDDK.
A solution containing 2.40 g (12.7 mmol) of acetal 14 in 20 mL of
EtOH and 5 mL of 10% HCl (v/v) was stirred for 3 h at room
temperature. After neutralization with solid NaHCO3, the solvent was
removed in vacuo and the residue was extracted with ether. The ether
layer was dried over anhydrous MgSO4, filtered, and concentrated, and
the residue was taken up in 30 mL of CH2Cl2. This solution was added
to 2.80 g (13.2 mmol) of ethyl 4-aminoheptanoate hydrochloride and
0.1 g of NaOAc in 50 mL of water, and the two-phase mixture was
refluxed for 4 h. After checking an aliquot by GC-MS for completion,
the cooled mixture was extracted with three 25 mL portions of ether,
and the combined ether extracts were dried over anhydrous MgSO4,
filtered, and distilled, to provide 1.36 g of 15 (38% yield), bp
(Kugelrohr) 125-130 °C (0.15 mmHg). GC-FTIR νmax 3112, 2968,
2942, 2883, 1750 (s), 1543, 1476, 1375, 1277, 1170 (s), 1113, 1039,
877, 772 cm-1; 1H NMR (400 MHz, CDCl3) δ 6.56 (1H, s), 6.12 (1H,
s), 5.83 (1H, s), 4.09 (2H, q, J ) 7 Hz), 3.97 (1H, m), 2.47 (2H, t, J
) 8 Hz), 2.09 (4H, br s), 1.95 (1H, m) 1.22 (3H, t, J ) 7 Hz), 1.13
(2H, m), 0.94 (3H, t, J ) 7 Hz), 0.87 (3H, t, J ) 7 Hz); 13C NMR (100
MHz, CDCl3) δ 173.48, 134.16, 115.41, 107.68, 104.59, 60.63, 54.46,
39.41, 31.79, 31.28, 30.83, 26.37, 22.88, 19.74, 14.42, 14.20, 14.17;
EIMS m/z 279 [M+] (18), 250 (5), 236 (17), 234 (12), 222 (10), 208
(5), 195 (10), 178 (8), 157 (10), 150 (25), 137 (9), 136 (8), 122 (28),
111 (18), 106 (15), 83 (25), 81 (15), 80 (100), 55 (43), 41 (52); HRMS
m/z 279.2154, calcd for C17H29NO2, 279.2198.
References and Notes
(1) Jones, T. H.; Blum, M. S.; Fales, H. M. Tetrahedron 1982, 38, 1949-
1958.
(2) Numata, A.; Ibuka, T. In The Alkaloids; Brossi, A., Ed.; Academic
Press: New York, 1987; Vol. 31, pp 193-315.
(3) Jones, T. H.; DeVries, P. J.; Escoubas, P. J. Chem. Ecol. 1991, 17,
2507-2517.
(4) Jones, T. H.; Gorman, J. S. T.; Snelling, R. R.; Delabie, J. H. C.;
Blum, M. S.; Garraffo, H. M.; Jain, P.; Daly, J. W.; Spande, T. F. J.
Chem. Ecol. 1999, 25, 1170-1193.
(5) Ritter, F. J.; Persoons, C. J. Neth. J. Zool. 1975, 25, 261-275.
(6) Jones, T. H.; Highet, R. J.; Blum, M. S.; Fales, H. M. J. Chem. Ecol.
1984, 10, 1233-1249.
(7) Jones, T. H.; Stahly, S. M.; Don, A. W.; Blum, M. S. J. Chem. Ecol.
1988, 14, 2197-2212.
(8) Jones, T. H.; Laddago, A.; Don, A. W.; Blum, M. S. J. Nat. Prod.
1990, 53, 375-381.
(9) Jones, T. H.; Torres, J. A.; Spande, T. F.; Garraffo, H. M.; Blum,
M. S.; Snelling, R. R. J. Chem. Ecol. 1996, 22, 1221-1236.
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Entomol. Soc. Am. 1974, 67, 525-526.
(11) Francke, W.; Schro¨der, F.; Walter, F., Sinnwell, V.; Baumann, H.;
Kaib, M. Liebigs Ann. 1995, 965-977.
(12) Schro¨der, F.; Sinnwell, V.; Baumann, H.; Kaib, M. Chem. Commun.
1996, 2139-2140.
(13) Schro¨der, F.; Francke, S.; Francke, W.; Baumann, H.; Kaib, M.;
Pasteels, J. M.; Daloze, D. Tetrahedron 1996, 52, 13539-13546.
(14) Schro¨der, F.; Sinnwell, V.; Baumann, H.; Kaib, M.; Francke, W.
Angew. Chem., Int. Engl. Ed. 1997, 36, 77-80.
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Science 2006, 311, 101-104.
(16) Daly, J. W.; Spande, T. F.; Garraffo, H. M. J. Nat. Prod. 2005, 68,
1556-1575.
(17) Sonnet, P. E.; Oliver, J. E. Lloydia 1975, 12, 289-294.
(18) Garraffo, H. M.; Spande, T. F.; Daly, J. W.; Baldessari, A.; Gros, E.
G. J. Nat. Prod. 1993, 56, 357-373. The E, Z nomenclature was
introduced by Sonnet and Oliver17 and has been used by us and others
generally for “izidine” stereochemical assignments. The E (entgegen)
and Z (zusammen) descriptors refer respectively to whether the CHs
at ring substituents are on opposite molecular faces or the same face
as the lowest numbered substitutent.
3-Butyl-5-propyl-8-oxo-5,6,7,8-tetrahydroindolizine (16). A solu-
tion containing 0.30 g (1.08 mmol) of pyrrole ester 15 in 10 mL of
anhydrous CH2Cl2 under argon was treated with 1.7 mL of 2 M BBr3
in CH2Cl2 at room temperature. After 40 min the solution was
neutralized with an excess of saturated NaHCO3 and the mixture was
extracted with three 25 mL portions of ether. The combined ether
extracts were dried over anhydrous MgSO4, filtered, and concentrated
in vacuo to provide 0.23 g of 16 that was 81% pure by GC-MS. GC-
FTIR νmax 2963, 2947, 2882, 1685 (s), 1541, 1476, 1422, 1397, 1332,
1242, 1187, 1121, 775 cm-1; EIMS m/z 233 [M+] (43), 191 (18), 190
(100), 176 (10), 163 (10), 162 (17), 149 (30), 148 (88), 135 (17), 120
(18), 106 (23), 80 (25), 79 (22), 78 (23), 55 (16), 41 (75); HRMS m/z
234.1859 ([M + 1]+), calcd for C15H24NO, 234.1858, 233.1823 ([M]+),
calcd for C15H23NO, 233.1780.
3-Butyl-5-propyl-8-hydroxyindolizidine (10a-d). In a typical
hydrogenation, a solution containing 30 mg (0.13 mmol) of 16, two
drops of triethylamine, and 60 mg of 5% Rh/Al2O3 in 10 mL of EtOAc
was shaken under 3 atm H2 overnight. Gas chromatographic analysis
revealed the presence of four isomers, 10a, 10b, 10c, and 10d, with an
88% combined yield in a 3:1:6:4.7 ratio having similar mass spectra.
10a: EIMS m/z 239 [M+] (1), 238 (1), 197 (3), 196 (29), 183 (11),
182 (100), 154 (13), 140 (9), 126 (4), 122 (3), 96 (5), 95 (4), 94 (7),
82 (10), 68 (12), 55 (30), 41 (50). 10b: EIMS m/z 239 [M+] (1), 238
(1), 197 (9), 196 (83), 183 (11), 182 (100), 154 (13), 140 (9), 126 (4),
122 (7), 96 (5), 95 (4), 94 (7), 82 (10), 68 (12), 55 (30), 41 (50). 10c:
EIMS m/z 239 [M+] (1), 238 (1), 197 (3), 196 (100), 183 (11), 182
(90), 152 (3), 140 (9), 126 (2), 122 (5), 96 (5), 95 (4), 94 (7), 82 (10),
68 (12), 55 (30), 41 (50). 10d: EIMS m/z 239 [M+] (1), 238 (1), 197
(3), 196 (68), 183 (11), 182 (100), 152 (3), 140 (9), 126 (2), 122 (2),
96 (5), 95 (4), 94 (7), 82 (10), 68 (12), 55 (30), 41 (50). In a different
hydrogenation experiment, run for 4 h, the ratio of 10a, 10b, 10c, and
10d was 3.5:1:3.6:1.8. The GC-FTIR spectra for 10a, 10b, 10c, and
10d are shown in Figure 4. HRMS for 10a: m/z 239.2316 ([M]+),
calcd for C15H29NO, 239.2249; 196.1735 ([M - C3H7 ]+), calcd for
C12H22NO, 196.1701; 180.1567 ([M - C4H9 ]+), calcd for C11H20NO,
180.1545. The GC-MS and GC-FTIR data for the first eluting isomer,
10a, were identical to those of the natural 10a. Minor amounts of
unreacted starting material 16 were seen at a longer GC retention time
than 10a-d. At a shorter retention time, equivalent amounts of the
7,8-dehydro-transformation product of 16 were seen. EIMS m/z 217
(28), 174 (M - Pr, 100), 160 (18), 146 (8), 144 (13), 133 (15), 132
(38), 130 (33), 118 (15), 117 (15), 91 (8), 77 (13); GC-FTIR νmax 3107,
3058, 2965, 2944, 2885, 1624, 1491, 1424, 1379, 1290, 1211, 1027,
(19) The Aldrich Library of FT-IR Spectra, Vapor Phase, Vol. 3; Pouchert,
C. E., Ed.; Aldrich Chemical Co.: Milwaukee, WI.
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therein).
(28) Garraffo, H. M.; Spande, T. F.; Jones, T. H.; Daly, J. W. Rapid
Commun. Mass Spectrom. 1999, 13, 1553-1563.
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762 cm-1
.

168 Journal of Natural Products, 2007, Vol. 70, No. 2
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NP068034T