Caste-specific tyramides from Myrmicine ants

Article abstract of DOI:10.1021/np900697s

Analysis of the extracts of male ants of Monomorium minimum and Monomorium ebeninum by GC-MS and GC-FTIR revealed the presence of tyramides 2 and 4c, for which the structures were established by comparison with synthetic samples. These compounds and their analogues 1 and 3 were also found in males of other Monomorium species, males of Myrmicaria opaciventris, and males of several Solenopsis (Diplorhoptrum) species. Vapor-phase FTIR spectra revealed critically important structural clues to two of the tyramides, which had methyl branching in the tyramide acyl moiety. Tyramide 4c exhibited a strong intramolecular amide NH hydrogen bond where an α-keto group was deduced to be present in the acyl moiety and also showed the overlap of this ketone group frecquency with that of the amide v_c-o The biological function of these compounds is uncertain; however, their role in ant-mating behavior may be suggested by a large body of evidence.

Full text of DOI:10.1021/np900697s

J. Nat. Prod. 2010, 73, 313–316
313
Caste-Specific Tyramides from Myrmicine Ants†
Tappey. H. Jones,*,‡ H. Martin Garraffo,§ Thomas F. Spande,§ Nirina R. Andriamaharavo,§ Jeffrey S. T. Gorman,‡
Alexander J. Snyder,‡ Andrew W. Jeter,‡ Juan A. Torres,⊥,| Roy R. Snelling,#,∇ and John W. Daly§,¶
Department of Chemistry, Virginia Military Institute, Lexington, Virginia 24450, Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of
Health, HHS, Bethesda, Maryland 20892-0820, International Institute of Tropical Forestry, P.O. Box 25000, Rio Piedras,
San Juan 00928-2500, Puerto Rico, and Los Angeles County Museum of Natural History, 900 Exposition BouleVard, Los Angeles, California 90007
ReceiVed October 29, 2009
Analysis of the extracts of male ants of Monomorium minimum and Monomorium ebeninum by GC-MS and GC-FTIR
revealed the presence of tyramides 2 and 4c, for which the structures were established by comparison with synthetic
samples. These compounds and their analogues 1 and 3 were also found in males of other Monomorium species, males
of Myrmicaria opaciVentris, and males of several Solenopsis (Diplorhoptrum) species. Vapor-phase FTIR spectra revealed
critically important structural clues to two of the tyramides, which had methyl branching in the tyramide acyl moiety.
Tyramide 4c exhibited a strong intramolecular amide NH hydrogen bond where an R-keto group was deduced to be
present in the acyl moiety and also showed the overlap of this ketone group frequency with that of the amide νCdO. The
biological function of these compounds is uncertain; however, their role in ant-mating behavior may be suggested by
a large body of evidence.
Ring-saturated nitrogen heterocycles are well-known components
of the venoms of ants in the subfamily Myrmicinae, particularly in
thegeneraMegalomyrmex,Monomorium,Myrmicaria,andSolenopsis.1–4
While different species of ants may have some of the same
alkaloids, the alkaloid composition of a particular species seems
to be characteristic, varying only with the age of the ants.5 In several
cases, a marked difference has been observed between the venom
alkaloids produced by queens and those produced by workers of a
particular species.6,7 The venom alkaloids found in the workers,
and in some cases the queens, of the species reported in this
investigation, Monomorium minimum, Monomorium pharaonis,
Monomorium floricola, Myrmicaria opaciVentris, Solenopsis mo-
lesta, and Solenopsis maboya, have been described, while those of
Monomorium ebeninum are very similar to those of M. miminum.1,7–9
These compounds are conspicuously absent in the extracts of all
male ants in these genera, which do not have venom glands. Herein
we describe, however, not the presence of alkaloids but the
occurrence of a set of acylated tyramines (1-3 and 4c) from males
of nine species of the genera Monomorium, Myrmicaria,, and
Solenopsis (Diplorhoptrum). Compounds 1-3 have been previously
reported from marine bacteria,10 while the R-ketoamide 4c is a new
compound.
Table 1. Distribution of Tyramides from Myrmicine Ants
species
dates collected
1
2
3
4c
M. minimum
M. ebeninum
M. floricola
1995 and 1996
1996 and 2003
1999
*
*
*
*
*
M. pharaonis
M. opaciVentris
S. nr. molesta
Solenopsis #11 PR
Solenopsis #78 PR
S. maboya
1999
2003
1993
1995
1998
1999 and 2000
*
*
*
*
*
*
collectedfromnestsinLexington,VA.Theinitialgaschromatography-mass
spectrometry (GC-MS) analysis of CH2Cl2 extracts of these
specimens revealed the presence of two compounds, 2 and 4c, for
which the mass spectra had m/z ) 120 (100) and a significant ion
at m/z 107. In one experiment, trisection of M. minimum revealed
by GC-MS that these compounds occur in the gaster of the ants.
Subsequently, males of the other species listed in Table 1 were
examined. Trisection of M. ebeninum showed that these compounds
also were found only in the gasters of the ants. Extracts of whole
ants only were available for the remaining species. Trisection of
myrmicine workers has never shown tyramides.
In M. minimum, the first component had the following. GC-FTIR
spectrum: νmax 3652, 3466, 3016, 2968, 2936, 2887, 1707(s), 1613,
1500(s), 1443, 1332, 1256, 1173, 1106, 821 cm-1. EIMS [M+] m/z
207 (2), 164 (1), 121 (13), 120 (100), 107 (41), 91 (1), 88 (24), 77
(22), 71 (36), 55 (5), 43 (77), 41 (25); HRMS m/z 207.1254, calcd
for C12H17NO2, m/z 207.1259. Its MS spectrum and GC retention
time (20.0 min) were identical with those of an authentic sample
of N-[2-(4-hydroxyphenyl)ethyl]butanamide (2).11
The second and roughly equimolar component at Rt 21.0 min
had the following. EIMS: [M+] m/z 249 (2), 234 (1), 206 (1), 164
(4), 121 (35), 120 (100), 107 (22), 91 (9), 85 (13), 77 (18), 57
(40), 43 (8), 41 (20). Initially, it was assumed that this component
was a three-carbon homologue of 2; however, the high-resolution
mass spectrum (HRMS m/z 249.1361, calcd for C14H19NO3, m/z
249.1365) indicated the presence of a third oxygen and another
double-bond equivalent. GC-FTIR of this component had νmax
3652, 3429, 3019, 2968, 2938, 2885, 1707(s), 1614, 1513(s), 1439,
Results and Discussion
In the summers of 1995 and 1996, males of the small black ant
M. minimum Buckley, common in the eastern United States, were
† Dedicated to the late Dr. John W. Daly of NIDDK, NIH, Bethesda,
Maryland, for his pioneering work on bioactive natural products.
* To whom correspondence should be addressed. Tel: (540)-464-7422.
Fax: (540)-464-7261. E-mail: jonesth@vmi.edu.
‡ Virginia Military Institute.
§ NIDDK, NIH.
⊥ International Institute of Tropical Forestry.
| Deceased June 5, 2004.
1365,1336, 1258, 1172, 1102, 820 cm-1. The frequency (3429 cm-1
)
of the secondary amide NH of this component was shifted to a
lower frequency by 37 cm-1, suggesting that an intramolecular
hydrogen bond was present. The lack of an obvious IR absorption
# Los Angeles County Museum of Natural History.
∇ Deceased April 21, 2008.
¶ Deceased March 5, 2008.
10.1021/np900697s  2010 American Chemical Society and American Society of Pharmacognosy
Published on Web 01/26/2010

314 Journal of Natural Products, 2010, Vol. 73, No. 3
Scheme 1. Synthesis of 2-Ketohexanoyltyramines 4a-4c
Jones et al.
on Celite, chromic acid/ether, Swern oxidation, and Dess-Martin
periodinane, but the Jones reagent at 0 °C for 10 min, although
providing low yields (10-20%), gave clean samples of the
R-ketoamides after flash chromatography. A great improvement
in the oxidations of 5a and 5c was achieved by air oxidation
with a catalytic amount of V2O5 in toluene at 90-100 °C,15
where 4a and 4c were obtained, respectively, in ca. 60% yield
after chromatography.
The straight-chain analogue (4a) was first synthesized and found
to be nonidentical with the natural tyramide, but it was recognized
by close inspection of the νCH region (see Figure 1) that the
asymmetric vibration at ca. 2968 cm-1 relative to the νCH methylene
stretching vibration at 2938 cm-1 indicated that another methyl
group was clearly present in the acyl moiety of the natural tyramide.
This “methyl-counting” method had earlier been applied by one of
us (H.M.G.) to the assignment of a tentative structure to a novel
homopumiliotoxin alkaloid 249F found in an Argentine toad.16
The C-H bending vibrations at ca. 1385 cm-1 gave no clear
evidence of a gem-dimethyl group, so a 2-keto-3-methylpentanoyl
tyramide (4b) was then synthesized. Although very similar in its
MS and IR spectra, it was not identical with the natural tyramide,
leaving 2-keto-4-methylpentanoyl tyramide (4c) as the remaining
likely structural possibility for the m/z 249 tyramide. Synthesis of
2-keto-4-methylpentanoyl tyramide (4c) finally revealed that the
natural m/z 249 tyramide possesses this same structure, despite the
fact that the gem-dimethyl absorption, expected for such an “iso”
structure, is not unambiguously evident. The MS spectrum, GC
retention time, and GC-FTIR spectrum of the natural tyramide
matched that shown for 4c, as depicted in Figure 1.
Evidence for oxygen functionality at the R position of the
tyramide acyl moiety was also deduced from the EIMS of the
natural m/z 249 tyramide, where a cleavage between the acyl amide
CdO and the adjacent ketone carbon is seen, giving an m/z 85
(12%) fragment, and a related weak but diagnostic fragment at m/z
164 (2.4%) is seen as an indication that both cleavage fragments
carry charge. No cleavage for 4c was observed between the acyl
carbonyl and the amide nitrogen, yielding a minor or even
significant fragment ion at m/z 130, which occurs in all of the other
tyramides lacking an R- keto- or R-hydroxyl substituent. The major
fragments of all of the tyramides are governed by cleavage at the
benzylic position to afford the m/z 107 ion (ca. 40%) and a
McLafferty rearrangement to yield as the base peak the m/z 120
ion, having a p-hydroxystyrene structure.
After the structures of 2 and 4c were established in males of M.
minimum and M. ebeninum, extracts of the other male ants listed
in Table 1 were examined and the structures of tyramides 1-3 were
determined by spectroscopic analysis and comparison with synthetic
material.11,17 These tyramides have not been detected in extracts
of workers or queens of any of the species in Table 1 over the
many years of this study.
i EDCI, HOBT, DMF.
ii Jones Reagent or O2, V2O5, toluene, ∆.
for the third oxygen, e.g., a ketone or epoxide functionality,
presumed to be in the acyl portion of the amide, was perplexing.
The six double-bond equivalents determined from HRMS in
comparison with the five found for 2 could be consistent with (1)
a hydroxy group and double bond, (2) an epoxide, (3) a ketone, or
(4) a ring with an ether oxygen. No additional hydroxy frequency
-1
was observed in addition to the sharp phenolic νOH at 3652 cm
nor was any internal/terminal olefinic νdCH absorption noted, ruling
out the first possibility. No unambiguous absorptions for an epoxide
could be ascertained, but an R-keto group in the acyl moiety could
not be excluded because a few examples that we were aware of
have this absorption coupled to the ester or amide absorption and
sometimes are seen as a single absorption band.12 Nonetheless, it
was assumed that an ether νCO might be present but was difficult
to detect by IR spectroscopy, and consequently three tyramides were
synthesized having a cyclic methyl, tetrahydrofuranyl ether, a
tetrahydropyranyl ether, or an R-ꢀ-epoxide group, all of which
might be expected to provide a hydrogen-bond receptor for the
observed amide NH donor. This synthetic work and that of other
preliminary structural possibilities for the m/z 249 tyramide will
be reported elsewhere. None fit the GC-MS or GC-FTIR behavior
of the m/z 249 tyramide so the structural possibility (4) above,
although biosynthetically attractive, was made less likely. Not all
permutations of cyclic ethers were synthesized because about this
time we discovered by a close examination of the amide I/amide
II band ratio in the m/z 249 tyramide IR spectrum the likely presence
of a ketone group in the acyl group, most probably in the R position.
This conclusion arose from the observation that the ratio of the
amide I to amide II bands in the natural molecular weight 249
tyramide was appreciably greater than that seen in 2 as well as
those seen with all of the other non-R-ketotyramides, where the
amide II band at 1500-1505 cm-1 is significantly more intense
than the amide I band. We concluded, therefore, that the stretching
vibration of the R-keto group coincides with that of the amide νCdO
group, enhancing its intensity, and is an example of the “coupling
effect” that has been reported for amides.13 The above-mentioned
shift in the amide NH to a lower frequency, which suggested
hydrogen bonding to an oxygen function, is consistent with an
R-keto group being a hydrogen-bond acceptor.
While the biological role of these tyramides is as yet undeter-
mined, their occurrence exclusively in males of the species
examined suggests that they may have a function in the mating
behavior in these ants, where a fair amount of field research already
exists that indicates a role for the involvement of some pheromone,
such as these compounds.18 Male-specific compounds have been
reported in other ant subfamilies for many years.19,20 Ant-mating
behavior can be divided into a female-calling syndrome and a male-
aggregation syndrome. In the latter, males first attract additional
males and the buildup of pheromones later attracts females.21 For
example, in a species of the myrmicine genus Crematogaster, the
males occupy the top portion of the swarm and the females are
attracted to that area and occupy the bottom portion of the swarm.22
Small amounts of the R-ketoamides (4a-4c) for a GC-MS
and GC-FTIR comparison with the natural R-ketoamide were
prepared by a careful oxidation of the corresponding R-hy-
droxyamides (5a-5c) with the Jones reagent at 0 °C (Scheme
1). The hydroxyamides 5a-5c formed nearly quantitatively by
coupling 2-hydroxyhexanoic acid, 2-hydroxy-3-methylpentanoic
acid, or 2-hydroxy-4-methylpentanoic acid14 with tyramine in
the presence of N-ethyl-N-[3-(dimethylamino)propyl]carbodi-
imide/1-hydroxybenzotriazole. Numerous oxidation methods of
the hydroxyamides were attempted, including PCC, PDC, CrO3
Of the genera examined here, in Monomorium ()Chelaner) both
syndromes have been observed for particular species.23 In M.
opaciVentris, it has been observed that the winged males leave the
nest first, followed by the alate females, and mating takes place in

Journal of Natural Products, 2010, Vol. 73, No. 3 315
Figure 1. FTIR vapor-phase spectrum of the natural R-ketotyramide from males of the ant M. minimum. Insets are of the νCH region of
synthetic 4a, 4c, and 4b from left to right.
and another in July 1996, and a third collection was made in July 2003
in Cayey, PR. One of the 1996 collections of M. ebeninum was trisected,
and their heads, thoraxes, and gasters were placed in separate vials
containing a small amount of methanol. M. floricola Jerdon males were
collected in May 1999 in Guaynabo, PR. M. pharaonis L. males were
collected in July 1996 in Gainesville, FL, and these ants were placed
in vials containing a small amount of methylene chloride for analysis.
M. opaciVentris workers, males, and queens were collected in March
2003 in Kakamega District, Isecheno, Kakamega Forest, Kenya, and
placed in vials containing methanol. Solenopsis nr. molesta were
collected in May 1993 in the Chuckawalla Mountains, Red Cloud
Canyon, 8 mi. south-southeast of Desert Center, Riverside County, CA.
S. maboya Snelling were collected in Guaynabo, PR, in February 1999
and January 2000, Solenopsis 11 males were collected in May 1995
near Guaynabo, PR, and Solenopsis 78 males were collected in June
1998 near Guaynabo, PR. The distribution of tyramides found in these
species is shown in Table 1. Voucher specimens have been deposited
in the entomological collection of the Los Angeles County Natural
History Museum.
flight, an activity that may imply the presence of an attractant or
flight-initiating signal emitted by the male ants.24 Finally, it should
be noted that the Solenopsis males that were available for this
investigation are members of the subgenus Diplorhoptrum, com-
monly known as “thief ants”, a group whose workers and queens
contain a wide variety of venom alkaloids.1,6 These ants are mostly
subterranean, with extremely difficult taxonomy, and very little is
known about their mating behavior.25 Collections 11 and 78 from
Puerto Rico may be Solenopsis azteca, Solenopsis pygmaea, or
Solenopsis torresi, previously described species of thief ants found
in the same region.25 Because the mating flights of congeneric ant
species have been observed to be separated spatially and tempo-
rally,26 the production of the same tyramide (3) in the thief ant
males as that in S. maboya may not be problematic if it were part
of their mating behavior. More research is needed to clarify the
role of these unusual and uncommon tyramides in the natural history
of myrmicine ants, in particular to confirm a role in mating.
N-[2-(4-Hydroxyphenyl)ethyl]-2-hydroxyhexanamide (5a). A so-
lution containing 0.26 g of 2-hydroxyhexanoic acid14 (2 mmol), 0.26 g
of tyramine, 0.27 g of 1-hydroxybenzotriazole (HOBT), and 0.4 g of
N-ethyl-N-[3-(dimethylamino)propyl]carbodiimide (EDCI) in 8 mL of
DMF was stirred overnight at room temperature. The solvent was
removed under reduced pressure, and the residue was partitioned
between 2% HCl and diethyl ether. The ether layer was dried over
anhydrous MgSO4. After filtration, the solvent was removed to provide
0.55 g of 5a: 13C NMR (100 MHz, DMSO-d6) δ 174.54, 156.31, 130.08
(2C), 130.05, 115.76 (2C), 71.61, 35.11, 34.74, 27.46, 22.74, 14.57
(the CH2NH signal was obscured by the solvent signal); EIMS [M+]
m/z 251 (1), 194 (1), 164 (1), 132 (4), 121 (17), 120 (100), 107 (12),
91 (3), 77 (6), 69 (5); HRMS m/z 251.1570, calcd for C14H21NO3, m/z
251.1521.
Experimental Section
General Experimental Procedures. GC-MS was carried out in
the electron impact (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 °C/min. Vapor-phase FTIR
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 and a temperature program
from 100 to 280 °C at 10 °C/min or occasionally slower ramps. Some
work used a Phenomenex “Inferno” column (30 m × 0.22 mm). 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 ionization (ESI) or APCI mode.
Ants. Two collections of M. minimum Buckley males were collected
in July 1995 and again in July 1996 in Lexington, VA. In each
collection, 10-20 individuals were obtained and placed in vials
containing a small amount of methanol for analysis. One of the 1996
collections was frozen while still alive; the frozen ants were trisected,
and their heads, thoraxes, and gasters were placed in separate vials
containing a small amount of methanol. A collection of M. ebinenum
Forel males was made in Guaynabo, Puerto Rico (PR), in June 1996
N-[2-(4-Hydroxyphenyl)ethyl]-2-hydroxy-3-methylpentana-
mide (5b). A solution containing 0.26 g of 2-hydroxy-3-methylpen-
tanoic acid14 (2 mmol) was condensed with tyramine as described for
5a to provide 0.8 g of a mixture that was 70% pure, with the remainder
1
being benzotriazole: H NMR (400 MHz, DMSO-d6) 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, br m);
13C NMR (100 MHz, DMSO-d6) δ 173.77, 156.27, 130.11 (2C), 130.08,
115.74 (2C), 75.72, 38.72, 35.11, 23.69, 16.31, 12.44 (the CH2NH signal
was obscured by the solvent signal); EIMS [M+] m/z 251 (1), 194 (2),

316 Journal of Natural Products, 2010, Vol. 73, No. 3
Jones et al.
164 (2), 132 (6), 121 (17), 120 (100), 107 (11), 91 (4), 77 (8), 45 (9);
HRMS m/z 251.1543, calcd for C14H21NO3, m/z 251.1521.
N-[2-(4-Hydroxyphenyl)ethyl]-2-hydroxy-4-methylpentana-
nr. molesta males and a great deal of archival work in the collections
at the Los Angeles County Museum of Natural History. We thank John
Lloyd for direct probe HRESIMS, Noel Whittaker for HRCIMS on
synthetic 4a-4c, and Lewis Pannell (all of NIDDK) for the original
HRMS of 2 and 4c. The research done at NIH was supported by the
intramural research funds of NIDDK.
mide (5c). A solution containing 0.26 g of 2-hydroxy-4-methylpentanoic
acid14 (2 mmol) was condensed with tyramine as described for 5a: 13
C
NMR (100 MHz, DMSO-d6) δ 174.93, 156.28, 130.14 (2C), 130.1,
115.75 (2C), 70.22, 44.17, 35.08, 24.54, 24.12, 22.20 (the CH2NH signal
was obscured by the solvent signal); EIMS [M+] m/z 251 (1), 194 (1),
164 (2), 132 (3), 121 (16), 120 (100), 107 (13), 91 (3), 77 (6), 45 (1),
43 (6); HRMS m/z 251.1521, calcd for C14H21NO3, m/z 251.1521.
N-[2-(4-Hydroxyphenyl)ethyl]-2-oxohexanamide (4a). A solution
containing 60 mg of 5a in 3 mL of toluene and 20 mg of V2O5 was
heated at 100 °C overnight. The cooled solution was filtered through
a short column of Florisil to provide 45 mg of 4a that was more than
75% pure by GC-MS analysis. No starting material remained: 1H NMR
of the crude material (400 MHz, CDCl3) δ 6.93 (2H, d, J ) 8.2 Hz),
6.74 (2H, d, J ) 8.2 Hz), 3.43 (2H, q, J ) 5 Hz), 3.41 (1H, m), 2.83
(2H, t, J ) 7 Hz), 2.68 (2H, t, J ) 6.8 Hz), 2.10 (1H, s), 1.50 (2H,
quintet, J ) 7 Hz), 1.25 (2H, sextet, J ) 7 Hz), 0.82 (3H, t, J ) 7.1
Hz); 13C NMR (100 MHz, CDCl3) δ 198.18, 159.17, 153.71, 128.84
(2C), 128.84, 114.63 (2C), 39.72, 35.44, 33.49, 24.20, 21.15, 12.79;
EIMS [M+] m/z 249 (1), 164 (5), 121 (30), 120 (100), 107 (25), 91
(6), 85 (9), 77 (13), 57 (20); HRCIMS ([M + H]+) m/z 250.1445, calcd
for C14H20NO3, m/z 250.1443.
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1
of 4b for spectroscopic analysis: H NMR (400 MHz, CDCl3) δ 6.97
(2H, d, J ) 8.2 Hz), 6.72 (2H, d, J ) 8.2 Hz), 3.44 (2H, q, J ) 5 Hz),
3.41, (1H, m), 2.70 (2H, d, J ) 7 Hz), 2.7 (2H, J ) 6.8 Hz), 2.08 (1H,
m), 1.01 (2H, d, J ) 7 Hz), 0.81 (3H, t, J ) 7.1 Hz); 13C NMR (100
MHz, CDCl3) δ 201.19, 159.08, 153.90, 128.75 (2C), 128.67, 114.63
(2C), 39.82, 39.37, 33.50, 24.38, 14.07, 10.45; EIMS [M+] m/z 249
(1), 164 (7), 121 (42), 120 (100), 107 (16), 91 (6), 85 (10), 77 (11), 57
(50); HRCIMS ([M + H]+) m/z 250.1442, calcd for C14H20NO3, m/z
250.1443.
N-[2-(4-Hydroxyphenyl)ethyl]-4-methyl-2-oxopentanamide (4c).
A solution with the same amounts of reactants (but with 5c instead of
5a) as those described for 4a provided 38 mg of 4c after flash
1
chromatography: H NMR (400 MHz, CDCl3) δ 6.97 (2H, d, J ) 8.2
Hz), 6.72 (2H, d, J ) 8.2 Hz), 3.44 (2H, q, J ) 5 Hz), 5.70 (2H, br
m), 2.70 (2H, t, J ) 6.8 Hz), 2.08 (1H, m), 0.86 (6H, d, J ) 6.8 Hz);
13C NMR (100 MHz, CDCl3) δ 199.06, 160.48, 154.83, 130.24, 130.03
(2C), 115.84 (2C), 45.48, 40.96, 34.75, 24.58, 22.75 (2C); EIMS [M+]
m/z 249 (3), 164 (7), 121 (37), 120 (100), 107 (20), 91 (3), 85 (9), 77
(9), 57 (25), 41 (8); HRCIMS ([M + H]+) m/z 250.1443, calcd for
C14H20NO3, m/z 250.1443.
(20) Brand, J. M.; Duffield, R. M.; MacConnell, J. G.; Blum, M. S.; Fales,
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395–420.
(22) Robertson, H. G.; Villet, M. J. Nat. Hist. 1989, 23, 767–773.
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Th.; Sykora, K. V. Insect. Soc. 2008, 55, 266–273.
The GC retention time and MS and FTIR spectra of 4c were identical
with those of the R-ketotyramides found in M. minimum, M. ebeninum,
and M. pharaonis.
Acknowledgment. We thank Lloyd Davis for the sample of M.
pharaonis males and Gordon C. Snelling for the sample of Solenopsis
NP900697S