William W. Epstein

Neotropical ant gardens. I. Chemical constituents.

In ant gardens of lowland Amazonia, parabiotic ant speciesCamponotus femoratus andCrematogaster cf.limata parabiotica cultivate a taxonomically diverse group of epiphytic plants, whose establishment is restricted to arboreal carton ant nests. Epiphyte seeds are collected by workers ofCa. femoratus, the larger of the two ants, and stored unharmed in brood chambers where they subsequently germinate. Although seeds of some ant-garden epiphytes bear nutritional rewards, previous studies have shown that these rewards are not sufficient to explain the pattern of ant attraction to seeds. Five aromatic compounds occur frequently in and on the seeds of most ant-garden epiphytes and may be chemical cues by which ants recognize propagules of their symbiotic plants. The most widely distributed of these is methyl 6-methylsalicylate [6-MMS]1, previously reported as a major mandibular gland product in relatedCamponotus species and present in trace quantities inCa. femoratus males. (−)-Citronellol6 (previously unreported inCamponotus) was the principal volatile constituent in extracts of male heads, and (−)-mellein7 was present in small quantities. Discovery of 6-MMS inside the mandibular glands of maleCa. femoratus (and its presence in analogous glands of related ants) offers preliminary support for Ules (1906) hypothesis that seeds attract ants by mimicking ant brood. In addition, the likely fungistatic activity of seed compounds suggests that they could retard microbial pathogens of ants and plants in the organic detritus of nest gardens. While the presence of identical seed compounds in so many unrelated plant lineages might represent a remarkable case of convergent evolution, other interpretations are possible.

Dynamics of 6-methoxybenzoxazolinone in winter wheat. Effects of photoperiod and temperature

Abstract6-Methoxybenzoxazolinone (6-MBOA), a compound derivable from some freshly growing plants, is known to stimulate reproduction in some mammals and birds. Winter wheat was studied under controlled laboratory conditions to determine the effects of photoperiod and temperature on derivable 6-MBOA content. Longer photoperiods decrease the amount of derivable 6-MBOA per gram of fresh material in 4-day-old wheat seedlings. Higher temperatures also decrease the amount of derivable 6-MBOA in 4-day-old wheat. 6-MBOA content decreases as the plant ages. Comparisons of only the first centimeter above the seed produced the same age-related result. 6-MBOA is concentrated in the meristematic region with decreasing amounts found in higher portions of the plant. Roots from 9-day-old plants contain 6-MBOA. Unsprouted wheat seeds contain negligible amounts of 6-MBOA. These results demonstrate that environmental variables have a significant effect on derivable 6-MBOA levels, but that under all the regimes studied, 6-MBOA is present in freshly sprouted wheat.

Neotropical ant gardens II. Bioassays of seed compounds.

A number of volatile compounds occur on the seeds of taxonomically unrelated ant-garden epiphytes in western Amazonia. In field trials in southeastern Peru, we assayed the responses of ant-garden ants (Camponotus femoratus) to these and structurally similar compounds applied to artificial “seeds” made from zeolite molecular sieves. Benzothiazole,2, present on seeds of eight ant-garden epiphytes, repelled ants over the range of concentrations tested, as did 1-(2-hydroxy-6-methylphenyl)ethanone,3, occurring on seeds of six ant-garden epiphytes. 2-Hydroxy-6-methylbenzoic acid, methyl ester (methyl-6-methylsalicylate, 6-MMS),1, found on seeds of at least nine ant-garden epiphytes, was mildly repellent at high concentration, but stimulated excitement, seed handling, and (rarely) seed carrying at lower concentrations. Vanillin,5, a seed compound of four ant-garden epiphytes, and limonene,6, a monoterpene from seeds of three ant-garden epiphytes, both stimulated excitement, alarm, seed handling, and (rarely) seed carrying. Identified from seeds of seven ant-garden epiphytes, 1-(2,4-dihydroxyphenyl)ethanone,4, elicited little or no response. Among 70 compounds tested (mainly aromatic compounds), those found on seeds of ant-garden epiphytes or having structural features in common with such compounds were the most attractive to the ants. Although not present on epiphyte seeds, 2-hydroxy-3-methoxybenzenemethanol,10, consistently stimulated seed transport to the nest in one year, but did so only rarely in subsequent years. Some of the volatile compounds on seeds of ant-garden epiphytes probably play a role in ant attraction to epiphyte seeds, but evidence remains ambiguous. Finally,Ca. femoratus responded to one test compound [1-(2-hydroxy-4-methoxyphenyl)ethanone,60] (absent from epiphyte seeds) by descending from the vegetation to the ground.

Volatile oil constituents of sagebrush

Abstract The volatile oil of Artemisia arbuscula arbuscula contained a new irregular monoterpene, 2,5-dimethyl-4-vinyl-1,5-hexadiene-3-ol (isolyratol), which was isolated and identified by spectral means. The optically pure furanoid (2S,5S)-trans-5-methyl-5-vinyltetrahydrofur-2-yl methyl ketone (arbusculone), was also characterized by transformation to known (2S,5S)-trans-linalyl oxide. The former component has never been isolated from natural sources prior to this study. The neutral pentane extract also contained several previously characterized non-head-to-tail monoterpenes including artemiseole, artemisia ketone, artemisyl acetate, methyl santolinate, and santolina triene, as well as the regular monoterpenes 1,8-cineole, camphor, p-cymene, camphene and the C6 fragment, terelactone.

The monoterpenes of Artemisia tridentata ssp. vaseyana, Artemisia cana ssp. viscidula and Artemisia tridentata ssp. spiciformis.

Monoterpenes from three different members of the Anthemideae family, Artemisia tridentata ssp. vaseyana, Artemisia cana ssp. viscidula and Artemisia tridentata ssp. spiciformis were isolated and their structures determined using spectroscopic techniques. A total of 26 irregular and regular monoterpenes were identified. Among these, 20 had previously been identified in the Anthemideae family. Of the remaining six, four were known, but previously unidentified in this family. 2,2-Dimethyl-6-isopropenyl-2H-pyran, 2,3-dimethyl-6-isopropyl-4H-pyran and 2-isopropenyl-5-methylhexa-trans-3,5-diene-1-ol were isolated from both A. tridentata ssp. vaseyana and A. cana ssp. viscidula. The irregular monoterpene 2,2-dimethyl-6-isopropenyl-2H-pyran has a carbon skeleton analogous to the biologically important triterpene squalene. Two additional irregular monoterpenes, artemisia triene and trans-chrysanthemal were isolated from A. cana ssp. viscidula and lavandulol was isolated from A. tridentata ssp. spiciformis. This is the first time a compound possessing a lavandulyl-skeletal type has been found in the Anthemideae family.

Metabolic intermediates in the biological oxidation of lanosterol to eburicoic acid

Abstract Eburicodiol and eburical as well as previously reported eburicol have been isolated from the neutral chloroform extracts of Formes officinalis . A triterpenic acid, identified as sulphurenic acid, has also been isolated.

p-Methoxyphenacyl esters as photodeblockable protecting groups for phosphates

p-Methoxyphenacyl esters of substituted phosphates have been found to be photosensitive protecting groups which may be useful in biologically important phosphate synthesis.

HIGH YIELD SYNTHESIS OF α-ALKOXYPHOSPHONIUM SALTS AND α-ALKOXYPHOSPHONATES

Abstract The recent work of Ley et al. 1 on α-alkoxyphosphorane compounds from cyclic enolethers has prompted us to report our findings in this area. In addition to cyclic enol ethers we have studied the acyclic case as well as the use of phosphite in place of triphenylphosphine. Using this approach we have prepared alkoxy-as well as 5-and 6-membered oxyheterocyclic phosphonium salts and phosphonates in high yield.

Eskimo uses ofArtemisia tilesii (Compositae)

A plant used by the southwestern Alaskan Eskimos for treatment of skin infections, chest colds and arthritis was identified asArtemisia tilesii Ledeb. (Compositae). The volatile constituents of this plant were identified as an 80:20 mixture of thujone and isothujone. Isothujone has codeine-like properties, which may help arthritic pain.

Synthesis of prenylated cysteines from serine derivatives

Prenylated cysteines are prepared by the reaction of serineβ-lactone with prenyl thiolate.