Kimiko Hashimoto

Simple analogs of acromelic acid, which are highly active agonists of kainate type neuroexcitant

The highly stereoselective synthesis of acromelic acid analogs; 3a and 3b, was achieved. The new kainoid 3b was found to be the strongest neuroexcitant among the kainoids known so far.

Syntheses of acyclic analogues of kainoids and neuroexcitatory activity

Abstract Four configurational isomers of 3-benzylglutamic acid, acyclic analogues of kainoids were synthesized to examine their structure-activity relationship.

Pigment chemistry: The red sweat of the hippopotamus

Within a few minutes of perspiration, the colourless, viscous sweat of the hippopotamus gradually turns red, and then brown as the pigment polymerizes. Here we isolate and characterize the pigments responsible for this colour reaction. The unstable red and orange pigments turn out to be non-benzenoid aromatic compounds that are unexpectedly acidic and have antibiotic as well as sunscreen activity.

Identification of the toxic trigger in mushroom poisoning

We have isolated the small, highly strained carboxylic acid cycloprop-2-ene carboxylic acid from the Asian toxic mushroom Russula subnigricans. This compound is responsible for fatal rhabdomyolysis, a new type of mushroom poisoning that is indicated by an increase in serum creatine phosphokinase activity in mice. We found that polymerization of the compound at high concentrations via ene reaction abolishes its toxicity.

Synthesis of new acromelic acid congeners : novel neuroexcitatory amino acids acting on glutamate receptor

Abstract A general synthetic method of acromelic acid congeners was developed. Various C4-substituents of this family was introduced by the substitution reaction of the corresponding tosylate with diaryl copper lithium. Phenyl derivative 11 showed comparable excitatory activity with kainic acid, and o -anisyl derivative 12 had most potent activity in this family.

β-Phenylselenoalanine as a dehydroalanine precursor–efficient synthesis of alternariolide (AM-toxin I)

Alternariolide (AM-toxin) is synthesized in 44% overall yield from L-2-amino-5-(4-methoxyphenyl)pentanoic acid; D-β-phenylselenoalanine is used as the dehydroalanine precursor.

Synthesis of acromelic acid A, a toxic principle of clitocybe acromelalga.

Abstract Acromelic acid A, a toxic principle of Clitocybe acromelalga , was synthesized from l -α-kainic acid. The synthesis established the previously inferred structure, and determined the absolute configuration as shown by 1 .

Absolute configuration and tautomeric structure of xylindein, a blue–green pigment of Chlorociboria species

The S absolute configuration of both chiral centers of xylindein was assigned using X-ray crystallographic heavy atom analysis after its conversion to a synthetic derivative. Crystallographic analysis of xylindein crystallized with phenols revealed that the proposed structure is the proper tautomer in the crystals.

Synthesis of conformationally restricted analogs of kainic acid. Is the conformation of the C4-substituent of kainoid important to its neuroexcitatory activity?

Abstract Conformationally restricted analogs of kainic acid, which have an azabicyclo[3.3.0]octane system, were synthesized through the intramolecular addition reaction of trimethylenemethane to the α,β-unsaturated ester. Every synthesized isomer showed very weak depolarizing activity. These results indicate that the plane of the isopropenyl group of kainic acid should be diagonal to the pyrrolidine ring to show potent activity.

Efficient syntheses of acromelic acids B and E, which are potent neuroexcitatory amino acids

(−)-Acromelic acid B(2) was synthesized from 2-cyano-3-(2-hydroxyethyl)pyridine(4) in 21% overall yield. Acromelic acid E(3) was also prepared on the way of above synthesis.