Hiroaki Okamura

Khayanolides, rearranged phragmalin limonoid antifeedants from Khaya senegalensis

Abstract Three new rearranged phragmalin-type limonoids, named khayanolides A, B and C, were isolated as insect antifeedant together with four known rings B,D-seco compounds, seneganolide, methyl angolensate and its 6-hydroxy and 6-acetoxy derivatives from the ether extract of the stem bark of Khaya senegalensis. The structure of new compounds was elucidated by spectroscopic means and the absolute structure of khayanolide A was established by X-ray analysis and CD study. The antifeedant activity of the isolated compounds was also reported.

Limonoid antifeedants from chinese Melia azedarach

Abstract Three new limonoid antifeedants, trichilin H, 12-acetyl and 7,12-diacetyltrichilin B, were isolated along with three known limonoids from the root bark of Chinese Melia azedarach . Their structures have been elucidated by spectroscopic analysis and chemical means.

Degraded limonoids from Melia azedarach

Two new degraded limonoids, azedararide and 12alpha-acetoxy fraxinellone, were isolated together with two known degraded limonoids, fraxinellone and fraxinellonone, as ichthyotoxic substances from the root bark of Melia azedarach. Their structures were elucidated by spectroscopic and chemical means.

Limonoids from Melia azedarach

A biogenetically interesting ring-C seco limonoid, salannal, and a potent insect antifeedant, meliacarpinin E, were isolated from the root bark of Chinese Melia azedarach, along with four known seco limonoids, salannin, deacetylsalannin, nimbolinin B and nimbolidin B. Their structures were elucidated by spectroscopic studies and their antifeedant properties were examined with the larvae of Spodoptera eridania.

Asymmetric synthesis of the key intermediate of an SP antagonist RPR107880 using a base-catalyzed Diels–Alder reaction

Abstract An asymmetric synthesis of the key intermediate of RPR 107880, a substance P antagonist, using a base-catalyzed Diels–Alder reaction of 3-hydroxy-2-pyrone and N -benzylmaleimide is described.

Three new antifeeding meliacarpinins from chinese Melia Azedarach Linn

Three new limonoid antifeedants, meliacarpinins 1–3, were isolated along with fourteen known limonoids from the root bark of Chinese Melia azedarach. Linn (Meliaceae). Their structures and antifeedant activity were elucidated.

A base catalyzed Diels-Alder reaction of 3-hydroxy-2-pyrone

Abstract A base catalyzed Diels-Alder reaction of 3-hydroxy-2-pyrone with various electron-deficient dienophiles gave cycloadducts in nearly quantitative yields. The reactions proceeded with complete stereospecificity and regioselectivity.

Azedarachin C, A limonoid antifeedant from Melia azedarach

Abstract A new limonoid, azedarachin C, was isolated as an insect antifeedant from the root bark of Chinese Melia azedarach and the structure was elucidated by spectroscopic means.

Three novel bis(indole) alkaloids from a stony coral, Tubastraea sp.

Three novel bis(indole) alkaloids with an unprecedented skeleton have been isolated from a stony coral, Tubastraea sp. These indoles could biogenetically be derived from two molecules of aplysinopsin via a Diels–Alder reaction.

Limonoids from the stem bark of Cedrela odorata

Four nomilin/obacunol derivatives and a swietenolide derivative, together with seven known limonoids, were isolated from stem bark of Cedrela odorata and their structures established by spectroscopic methods. Antifeedant activity of the isolated compounds was also tested.