Tetsuto Tsunoda

Symbiotic bacterium modifies aphid body color.

Turncoat Aphids Aphid color has consequences for the fate of the wearer: Coccinellid beetles prefer to eat red ones and parasitoid wasps attack green ones. What might happen if aphids could change color and outwit their predators? Tsuchida et al. (p. 1102) have found that a subpopulation of the pea aphid can do this, but not without help from a previously unknown species of bacterium that lives intimately with the aphid as an endosymbiont and makes red aphids turn green. The bacterium interferes with host pigment biosynthesis—itself borrowed from fungi long ago in evolution—to stimulate blue-green pigment production as the aphid larva matures, turning the red nymph into a green adult. The ecological consequences of this about-turn of color have yet to be tested, but other studies have shown a variety of effects on aphid behavior mediated by endosymbionts in response to adaptation to different food plants, temperature tolerance, and predator avoidance. Infection with a symbiotic bacterium leads to a spectacular phenotypic change in its host, making red aphids turn green. Color variation within populations of the pea aphid influences relative susceptibility to predators and parasites. We have discovered that infection with a facultative endosymbiont of the genus Rickettsiella changes the insects’ body color from red to green in natural populations. Approximately 8% of pea aphids collected in Western Europe carried the Rickettsiella infection. The infection increased amounts of blue-green polycyclic quinones, whereas it had less of an effect on yellow-red carotenoid pigments. The effect of the endosymbiont on body color is expected to influence prey-predator interactions, as well as interactions with other endosymbionts.

1,1'-(azodicarbonyl)dipiperidine-tributylphosphine, a new reagent system for Mitsunobu reaction

Abstract The 1,1′-(azodicarbonyl)dipiperidine (ADDP)-tributylphosphine (TBP) system was developed as a new institute of the Mitsunobu reagent. The new system activates nitrogen or carbon nucleophiles, known to be innert or poorly reactive with the Mitsunobu reagent. to react with alcohols satisfactorily forming C-N or C-C bonds. The inversion of stereogenic carbinyl carbons was confirmed in the acylaltion reaction of two sec-alcohols.

CARBON-CARBON BOND FORMATION WITH NEW MITSUNOBU REAGENTS

Abstract The efficiency of three azodicarboxylic acid derivatives and a stabilized phosphorane in the Mitsunobu type CC bond formation was compared utilizing the reactions of three nucleophiles of different pKa′S and several alcohols of different structure types. The study established the characteristics of each reagent. The synthesis of two insect pheromone analogs was accomplished effectively using these homologation reactions.

Mitsunobu acylation of sterically congested secondary alcohols by N,N,N′,N′-tetramethylazodicarboxamide-tributylphosphine reagents

Abstract Four secondary alcohols of different steric environment reacted with five carboxylic acids of different acidity in the presence of N , N , N ′, N ′-tetramethylazodicarboxamide and tributylphosphine to give the corresponding epi-esters in better yield than with diethyl azodicarboxylate-triphenylphosphine in most cases. Of special merit is the combination of the new reagent system with p -methoxybenzoic acid to achieve complete inversion of sterically congested secondary alcohols.

Novel reactivity of stabilized methylenetributylphosphorane : a new Mitsunobu reagent

Abstract Cyanomethylenetributylphosphorane was shown to mediate the direct condensation of alcohols with O - and N -nucleophiles. A secondary alcohol, 2-octanol, reacted satisfactorily with Walden inversion of its carbinyl carbon.

Formation of heterocycles by the Mitsunobu reaction. Stereoselective synthesis of (+)-α-skytanthine

Abstract Cyanomethylenetributylphosphorane was shown to mediate the dehydrocyclization of diols and amino alcohols to give the corresponding 6-membered O- and N-heterocycles in 90% or better yields. Using the reaction as a key step, (+)-α-skytanthine, a unique mono terpene alkaloid, was synthesized stereoselectively.

MITSUNOBU-TYPE ALKYLATION WITH ACTIVE METHINE COMPOUNDS

Abstract Intermolecular reaction of two active methine compounds with primary or secondary alcohols in the presence of new Mitsunobu-type reagents afforded alkylation products in excellent (with primary alcohols) to fair yields (with secondary alcohol) except one case. It demonstrates that the new reagents, especially cyanomethylene-trimethylphosphorane, are excellent mediators for this type of alkylation. The double alkylation of an active methylene compound with diols under similar conditions gave cyclization products in good to excellent yields.

Asymmetric aza-Claisen rearrangement of glycolamide and glycinamide enolates. Synthesis of optically active α-hydroxy and α-amino acids

Abstract The aza-Claisen rearrangement of the enolates of N -crotyl glycolamide and glycinamide proceeded with excellent syn : anti (98:2) and facial selectivities (89:11). Optically pure (−)-verrucarino-lactone and D-allo -isoleucine were derived from the rearrangement products.

A FACILE ONE-POT CYANATION OF PRIMARY AND SECONDARY ALCOHOLS. APPLICATION OF SOME NEW MITSUNOBU REAGENTS

Abstract Some new Mitsunobu reagents, especially N,N,N′,N′ -tetramethylazodicarboxamide (TMAD)-tributylphosphine (TBP) and cyanomethylenetrimethylphosphorane (CMMP), mediated the direct transformation of primary and secondary alcohols into the corresponding nitriles in the presence of acetone cyanohydrin. This type of cyanation process can convert 3β-cholestanol to 3α-cyanocholestane in high yield with complete Walden inversion.

Asymmetric Induction in Aza-Claisen Rearrangement of Carboxamide Enolates. Effect of Chiral Auxiliary on Nitrogen.

Abstract Aza-Claisen rearrangement of enolates of N-alkyl-N-(2E)-butenylpropanamides with chiral alkyl groups proceeded with high relative asymmetric induction as well as excellent internal asymmetric induction to give optically active N-alkyl-Psyn-2,3-dimethylpent-4-enamides.