Robert Ottinger

Chemical defence in chrysomelid larvae and adults

Abstract The defensive secreation of several species of chrosomelid larvae and adults have been analyzed. Salicyaldehyde and some already known methylcyclopentanoid monoterpenes have been identified in the larvae. In the adults of the tribe Phaedonini, two isoxazolin-5-one derivatives (8 and 9) were isolate and their structures determined. The chemical defence of chrysomelid beetles is briefly reviewed with emphasis on chemataxonomy and ecological significance.

Two new guanidine alkaloids from the Mediterranean sponge Crambe crambe

Crambine A (1) and B (2) were isolated from the Mediterranean sponge Crambe crambe. Their structures were determined mainly by extensive NMR 2D experiments at 600 MHz.

Phosphoglucoisomerase-catalyzed interconversion of hexose phosphates: isotopic discrimination between hydrogen and deuterium.

SummaryThe discrimination between the isotopes of hydrogen in the reaction catalyzed by yeast phosphoglucoisomerase is examined by NMR, as well as by spectrofluorometric or radioisotopic methods. The monodirectional conversion of D-glucose 6-phosphate to D-fructose 6-phosphate displays a lower maximal velocity with D-[2-2H]glucose 6-phosphate than unlabelled D-glucose 6-phosphate, with little difference in the affinity of the enzyme for these two substrates. About 72% of the deuterium located on the C2 of D-[1-13C,2-2H]glucose 6-phosphate is transferred intramolecularly to the C1 of D-[1-13C,1-2H]fructose 6-phosphate. The velocity of the monodirectional conversion of D-[U-14C]glucose 6-phosphate (or D-[2-3H]glucose 6-phosphate) to D-fructose 6-phosphate is virtually identical in H2O and D2O, respectively, but is four times lower with the tritiated than 14C-labelled ester. In the monodirectional reaction, the intramolecular transfer from the C2 of D-[2-3H]glucose 6-phosphate is higher in the presence of D2O than H2O. Whereas prolonged exposure of D-[1-13C]glucose 6-phosphate to D2O, in the presence of phosphoglucoisomerase, leads to the formation of both D-[1-13C,2-2H]glucose 6-phosphate and D-[1-13C,1-2H]fructose 6-phosphate, no sizeable incorporation of deuterium from D2O on the C1 of D-[1-13C]fructose 1,6-bisphosphate is observed when the monodirectional conversion of D-[1-13C]glucose 6-phosphate occurs in the concomitant presence of phosphoglucoisomerase and phosphofructokinase. The latter finding contrasts with the incorporation of hydrogen from 1H2O or tritium from 3H2O in the monodirectional conversion of D-[2-3H]glucose 6-phosphate and unlabelled D-glucose 6-phosphate, respectively, to their corresponding ketohexose esters.

7-O-methylapigeninidin, an anthocyanidin from Sorghum caudatum

A new anthocyanidin was isolated from the grains of Sorghum caudatum and identified as 7-O-methylapigeninidin on the basis of spectral data. This pigment was found in low concentration both in grains and in leaf sheaths.

Reconsideration of the Internal Tetramethylsilane Reference for Proton Magnetic Resonance Studies

The hypotheses implicit in the choice of tetramethylsilane (TMS) as an internal reference for liquid‐phase proton magnetic resonance spectra are examined. Experiments are designed to test the postulated chemical inertness, and the equality of van der Waals shifts for TMS and the solute. It is found that TMS, as well as GeMe4, or PbMe4, gives rise to interactions with aromatic solvents such as pyridine, nitrobenzene, benzaldehyde, benzonitrile, or aniline. The apparent heat of formation for these complexes are in the 1‐2‐kcal/mole range, while the observed chemical shifts are of the order of 0.10‐0.15 ppm. Caution is therefore urged in the use of TMS, and suitable molecules, not presenting these effects, are suggested for internal referencing.

NMR and stereochemical studies of non aromatic heterocyclic compounds-II. 13C and 31P NMR of 2-methoxy-1,3,2-dioxaphosphorinanes

Abstract 13 C and 31 P chemical shift data for eight 2-methoxy-1,3,2-dioxaphosphorinanes are reported. Examination of pairs of geometrical isomers, which differ only in the orientation of the OMe substituent on P III , have shown that both the 31 P and the 13 C signals of C 4,6 atoms appear 3–4 ppm at higher field when the OMe is axial compared with the equatorial isomer. This observation can be associated with the 1–3 syn diaxial interaction between the phosphorus axial substituent and the axial hydrogens on C 4,6 and should thus constitute, in the future, a supplementary tool for the structural analysis of this kind of compound. Important long range δ effects were observed both on 13 C and especially on 31 P chemical shifts. It is suggested that the high field δ e effects could reflect a direct stereoelectronic interaction between the P atom and the cyclic C-5 atom. This interpretation is supported by a study of the 31 P… 13 C coupling constants and their stereochemical dependence.

ABSOLUTE CONFIGURATION OF (3R,4S)-4-METHYL-3- HEXANOL--A PHEROMONE FROM THE HEAD OF THE ANT TETRAMORIUM IMPURUM FOERSTER

Abstract The isolation of 4-methyl-3-hexanol and 4-methyl-3-hexanone from the heads of all adult castes of T. impurum (previously wrongly reported as T. caespitum is described. The important quantitative differences between the secretions of both sexes is confirmed, males producing much higher quantities of both compounds. The absolute configuration of the alcohol from the heads of males was found to be 3R,4S. In view of the sexual differences observed in T. impurum , the qualitative divergence in the secretions of T. impurum and T. caespitum is tentatively interpreted as a biochemical isolation mechanism between two sibling species.

Acylated anthocyanins from the flowers of Ipomoea asarifolia

Abstract Among several anthocyanins detected in the flowers of Ipomoea asarifolia, two acylated anthocyanins were isolated and studied using chemical, GC, mass spectrometric and extensive NMR methods (TOCSY-1D, DQF-COSY and HMBC measurements). The first anthccyanin was identified as cyanidin 3-O-[2-O-(6-O-(E- caffeoyl )-β- d -glucopyranosyl )-6-O-(E- caffeoyl )-β- d -glucopyranoside ]-5-O-[β- d - glucopyranoside ] , and the new structure as cyanidin 3-O-[2-O-(6-O-(E-p- coumaroyl )-β- d -glucopyranosyl) -6-O-(E- caffeoyl )-β- d -glucopyranoside ]-5-O-[β- d - glucopyranoside .

Chemical studies of marine invertebrates. XXVII. On the absolute configuration of aromadendrane sesquiterpenes from the soft coral Cespitularia aff. subviridis

Allo-aromadendrene, (-) viridiflorol and (+) ledol have been identified as minor constituents of the soft coral Cespitularia aff. subviridis.

Spectres IR, dans la région ν(CO), d'halogénocyclohexanones et de leurs analogues α,α′-deutériés implications conformationnelles

Abstract I.R. spectra of sixteen halogeno cyclo hexanones and α,α′ deutero derivatives have been studied in the 1700–1800 cm −1 frequency range. For some halogenoketones; namely cis 2,6-dichloro cyclo hexanone, trans 2-bromo-5-methyl cyclo hexanone, 2-bromo cyclo hexanone and 2-chloro cyclo hexanone, the observed behaviour is not the same for the hydrogenated and deuterated compound. It seems that the ν(CO) region of hydrogenated compounds is “anomalous”. For the two first compounds cited above, a Fermi resonance between fundamental ν(CO) and the fist harmonic of a low frequency band seems a good explanation. In the case of bromo- and chloro cyclo hexanone, the explanation is not clear but it remains that a conformational justification alone is insufficient to explain the ν(CO) region of the hydrogenated compounds but sufficient for the deuterated compounds.