13C NMR of some insect attractants and related compounds

Long chain electrophilic contact poisons from the Dufour's gland of the ant Crematogasterscutellaris (Hymenoptera, Myrmicinae)

“…These results demonstrated that, in the major compound D, the double bond is located between C-16 and C-17, and between C-14 and C-15 in its isomer C. Finally, the geometry of these double bonds was assigned as Z, on the basis of a ' H / '~C nmr heterodecoupling experiment, allowing us to assign the signals of the allylic carbon atoms at 27ppm (25). Since this experiment was performed on the crude secretion, the geometry of the isolated double bond must also be Z in all other A16 and A14 derivatives whose structures will be discussed shortly.…”

Acyl transfer reactions with phosphine oxides: synthesis of E-homoallylic alcohols, cyclopropyl ketones, and γ-hydroxy ketones

“…We made (21e) because of the potential of such compounds in Murphy's tetralone ~ynthesis. '~ Synthesis of' y-Hydroxy Ketones.-The intermediate (19) is diverted to a third product, the hydroxy ketone (22), if the enolate anion can be protonated and the phosphinate ester hydrolysed to deprive the intermediate both of its nucleophile and its leaving group. Aqueous sodium hydroxide with enough ethanol to dissolve the phosphine oxide (8) gives reasonable yields of the hydroxy ketone ( 22) (Table 4), though some cyclopropyl ketone ( 21) is usually formed as well.…”

Venom Constituents of Three Species of Crematogaster Ants from Papua New Guinea

“…The presence of a furan ring conjugated to a double bond was further established by the fragmentation pattern in HREIMS [diagnostic fragment ions at m / z 94.0421 (calcd for C 6 H 6 O, 94.0418) and 107.0493 (calcd for C 7 H 7 O, 107.0497)] and by UV (λ max 259, 265, and 276 nm). The presence of an isolated disubstituted double bond was also proved by NMR (δ H 5.32, 2H, m; δ C 130.3), its stereochemistry being assigned as Z on the basis of the chemical shift of the allylic carbon atoms (δ 26.9 and 27.1). To fully establish the structure of fraction B components, it remained only to determine the position of the isolated double bond.…”