Characteristic secondary metabolites are currently acknowledged to play a pivotal role in the circumscription of a plant's insect fauna. A newly discovered association between wood–boring longicorn beetles (Cerambycidae) and their host trees belonging to the Brazil nut family (Lecythidaceae) inspired a yearlong rearing project in the lowland Neotropical rain forest of central French Guiana. Branches severed from five species of Lecythidaceae yielded 1813 cerambycids belonging to 37 species. Two of the five tree species, Couratari stellata and Gustavia hexapetala, yielded impoverished complements of cerambycids that included large percentages of generalists. Both tree species are characterized by fetid odors. Wood samples collected from the malodorous C. stellata, as well as from two well–colonized species, Lecythis poiteaui and Eschweilera coriacea, were analyzed for their volatile components. Sulfur compounds accounted for almost 15 percent of the volatiles detected from C. stellata, while they were at most minor components of the two well–colonized tree species. S–methylmethionine, isolated from a C. stellata wood sample, appeared to be the major sulfur compound contributing to the distinctive smell. We hypothesize that this foul odor is a deterrent to specialist cerambycids seeking oviposition sites.

bornyl acetate, 5257-37-4; endo-dehydronorbornyl acetate, 2890-95-1. methanol (1:4) and placed in an 8 X 0.375 in. Pyrex tube. The sample was handled as outlined above; after 100 hr of irradiation, the l H NMR spectrum showed no change.Nortricyclyl chloride (200 mg, 1.6 mmol) in 5.0 ml of chlorobenzene treated similarly showed no change in the l H NMR spectrum, even after 75 hr of irradiation.Irradiation of exo-Dehydronorbornyl Chloride (5) in Chlorobenzene-Methanol. exo-Dehydronorbornyl chloride (250 mg, 1.94 mmol) was dissolved in 5.0 ml of chlorobenzene-methanol (1:4) solution and the sample was treated as outlined for nortricyclyl chloride. After 75 hr of irradiation, l H NMR analysis indicated that the product was composed of 20% of 5 and 80% of saturated compounds, of which a t least 80% was dimeric or polymeric material. No absorption corresponding to -0Me could be detected.Irradiation of exo-Dehydronorbornyl Chloride (5) in Chlorobenzene. To two Pyrex tubes were added, respectively, 47 mg (0.37 mmol) and 85 mg (0.66 mmol) of 5 in 1.0 ml of chlorobenzene. The samples were then treated as outlined above. After 100 hr of irradiation, lH[ NMR analysis indicated that the first tube contained 56% of 5 and 44% of dimeric or polymeric material, while the second contained 43% of 5 and 57% of dimeric or polymeric material. No isomerization was detected.Quantum Yield Determination for exo-Norbornyl Chloride (7) and endo-Norbornyl Chloride (8). exo-Dehydronorbornyl chloride (5, 29.5 mg, 0.230 mmol) was diluted to 3.0 ml with acetone and placed in a preconstricted Pyrex test tube. The sample was degassed on a vacuum line and sealed at pressures less than 10-5 Torr. After irradiation for 48 hr, analysis by gas chromatography (25% Carbowax 20M on Chromosorb P 60/80,6 ft X 0.25 in. A1 column) indicated that the tube contained 20% of 7 (6 = 0.007).endo-Dehydronorbornyl chloride (6) treated similarly gave 12% of 8 after 48 hr (4 = 0.002).(8) pMethoxyacetophenone, rather than acetophenone, was employed as sensitizer owing to the latter's interference with one of the anticipated products during GC anaiysls. (9) (a) (16) 5.5-Dichloro-2-norbornene was synthesized using a modification of a general procedure [J. 0. Dinwiddle, Jr., and S. P. McManus, J. Org. Chem., 30,766 (1965)] and exhibited properties identical with those reported by Schleyer." (17) P. Laszloand P. v.Epoxidation of valencene (1) gives predominantly the @-epoxide 3,.and similarly, dihydrovalencene (15) gives predominantly 20. Photosensitized oxidation of 1 gives 4a,lOa-dimethyl-6@-isopropenyl-A1-9@-octalol (5) and 4cr,10a-dimethyl-6@-isopropenyl-As-la-octalol (6). Epoxidation of nootkatone (2) gives @-epoxide 10, which undergoes the Wharton-Bohlen rearrangement to @-octal01 5. Hydroboration of dihydrovalencene (15) gives predominantly 4a,lOa-dimethyl-6@-isopropyl-trans-I@-decalol (16). Stereochemical correlations are made and the results are discussed in reference to similar oxidations of other octalin derivatives.

Irradiation of nopinone in methanol gives an 80:20 mixture of cfs-l-formyl-2,2-dimethyl-3-vinylcyclobutane (3) and 3-(2',2'-dimethyl-A3'-cyclobutenyl)-l-propanal (7). Irradiation in ieri-butyl alcohol gives 3, 7, and 4-isopropenyl-5-hexenal (4).Cycloalkanones are well known1 to undergo photochemical a cleavage to give ketenes and/or unsaturated

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Nopinon (I) reagiert bei der Photolyse zu den beiden Spaltprodukten (II) und (III), bei längerer Bestrahlung entsteht, auch unabhängig aus (II), lediglich 4‐ Isopropenyl‐5‐hexenal (III).