Romalea microptera

Meinwald, J., K. Erickson, M. Hartshorn, Y. C. Meinwald, and T. Eisner (1968). Defensive mechanisms of arthropods. XXIII. Anallenic sesquiterpenoid from the grasshopper Romalea microptera. Tetrahedron Lett. 25 2959-2962. 

These last years, several syntheses of natural products using an iron-catalyzed reaction of Grignard reagents have been published. In 1969, Meinwald and Hendry used the reaction discovered by Kharasch and Tawney to prepare an allenic sesquiterpenoid isolated from the grasshopper Romalea Microptera (Scheme 61). 

Trimethylsilyl ethers are much more volatile than usual ethers and hence well suited for gas-liquid chromatography. Thus Meinwald6 was unable to effect direct purification of an allenic sesquiterpenoid (1), the defensive substance of the grasshopper Romalea microptera however, the bistrimethylsilyl derivative was purified without difficulty by gas-liquid... 

The defensive excretion of the grasshopper Romalea microptera contains the allenic ketone (10). This structure is clearly related to neoxanthin (57). Racemic samples of (10) were synthesised by two routes (Scheme 5) and, although there were some differences between the two products, their n.m.r. spectra show that they belong to the natural series and that they are clearly different from the photochemically synthesised isomer (3-OH, 90, R = Ac). The stereochemistry of the synthetic racemate was shown by X-ray crystallography to be the same as an optically active sample derived from the degradation of fucoxanthin. The absolute stereochemistry of the latter sample presumably also applies to the grasshopper ketone itself. 

The grasshopper Romalea microptera, produces a foam which contains"grass-hopper ketone" as a repel-lant towards its enemies such as ants. 

The grasshopper Romalea microptera discharges a foam from glands when disturbed. The principal constituent of the foam is romallenone (Figure 10.18) an allenic sesquiterpene. This compound is thought to be... 

The secretion of the grasshopper Romalea microptera contains, in addition to romallenone (Figure 10.18) verbenone, isophorone and 2,6,6-trimethylcyclohex-2-en-l,4-dione, below. What is the Ukely source of these compounds ... 

The large, flightless grasshopper, Romalea microptera excretes a novel sesquiterpenoid allenic ketone in its defensive secretionsJ Meinwald and Hendry confirmed the proposed structure and stereochemistry of this ant-repellant substance by stereospecific synthesis from isophorone. 

Component of arthropod defensive secretions isol. from the grasshopper Romalea microptera. Metab. of Streptothrix chromogena. Dienophile, H acceptor for Oppenauer oxidns., mild dehydrogenating agent. 

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