Nobuo Kato

Erinacine Q, a New Erinacine from Hericium erinaceum, and its Biosynthetic Route to Erinacine C in the Basidiomycete

Erinacines as cyathane-xylosides are known to have potent stimulating activity for nerve-growth-factor synthesis. Our search for new cyathane metabolites from a liquid culture of Hericium erinaceum YB4-6237 resulted in the isolation of a new erinacine named erinacine Q (1). NMR spectrometry and a chemical derivation from erinacine P (2) determined the compound to be a derivative in which the formyl group of erinacine P had been reduced to the hydroxymethyl group. To clarify the biosynthetic relationship between erinacine Q and the others, [1′-13C]erinacine Q ([1′-13C]-1) was chemically derived from [1′-13C]erinacine P ([1′-13C]-2) which had been prepared by feeding [1-13C]-D-glucose to the basidiomycete. The biotransformation of labeled erinacine Q into [1′-13C]erinacine C ([1′-13C]-5) via [1′-13C]erinacine P in this basidiomycete was demonstrated by NMR spectrometry.

Isolation of erinacine P, a new parental metabolite of cyathane-xylosides, from Hericium erinaceum and its biomimetic conversion into erinacines A and B

Abstract A new cyathane-xyloside, erinacine P, was isolated from mycelia of basidiomycetous Hericium erinaceum YB4-6237 in a shaken culture. Since its aglycon closely resembles typical cyathane diterpenoids such as cyathins and cyathatriols in its substitution pattern, this glycoside seems to be an important metabolite in the biosynthesis of erinacines and striatins. In fact, according to our biogenesis studies, erinacine P can be successfully converted chemically into erinacine B and, further, to erinacine A under mild conditions.

Total synthesis of optically active cotylenol, a fungal metabolite having a leaf growth activity. Intramolecular ene reaction for an eight-membered ring formation

Starting from condensation of two iridoid synthons, (3S,8R)-benzyloxy-1-iriden-7-al and (3R)-7-chloro-1-iridene, cotylenol, one of the representative fusicoccane diterpenoids having 5-8-5-membered tricyclic carbon framework, is now synthesized for the first time via an eight-membered ring formation by an intramolecular ene reaction and subsequent introduction of an α-hydroxyl group.

Structural Confirmation of Cotylenin A, a Novel Fusicoccane-diterpene Glycoside with Potent Plant Growth-regulating Activity from Cladosporium Fungus sp. 501-7W

The structure of cotylenin A, a potent plant-growth stimulant with the most complex molecule in cotylenins from Cladosporium fungus sp. 501-7W, was analyzed again by HMBC experiments and X-ray crystallography of its diacetyl-dihydroderivative. The previously proposed stereostructure of cotylenin A was thus completely confirmed.

Isolation of (−)-cyatha-3,12-diene, a common biosynthetic intermediate of cyathane diterpenoids, from an erinacine-producing basidiomycete, Hericium erinaceum, and its formation in a cell-free system

Cyatha-3,12-diene, a diterpene hydrocarbon having a 5–6–7-membered tricyclic skeleton, has been isolated for the first time from an erinacine-producing basidiomycete, Hericium erinaceum YB4-6237. This hydrocarbon had been formulated by Ayer et al. as a common biosynthetic intermediate of cyathane diterpenoids. Its stereo-structure, including the absolute configuration, has been unambiguously confirmed by its semi-synthesis from erinacine P, and its cell-free conversion from all-trans-geranylgeranyl diphosphate was demonstrated.

Total synthesis of albolic acid and ceroplastol II, 5–8–5-membered tricyclic insect sesterterpenoids, via a lactol-regulated silyloxy–Cope rearrangement

Optically active albolic acid and ceroplastol II, 5–8–5-membered tricyclic sesterterpenoids, were stereoselectively synthesised from two C10 synthons (iridoids)via CrCl2-condensation, lactol-regulated silyloxy–Cope rearrangement with a normally disfavoured boat transition geometry, TiCl2-ring closure, and C5-homologation.

Conversion of [19-2H2]fusicocca-2,10(14)-diene into its 8β-ol and fusicoccins by Phomopsis (Fusicoccum) amygdali

Abstract Feeding experiments of (+)-[19-2H2]fusicocca-2,10(14)-diene, a deuterated derivative of a new candidate for the initially-forming fusicoccane-hydrocarbon in the fusicoccin biosynthesis, with the fusicoccin-producing fungus Phomopsis (Fusicoccum) amygdali have revealed its incorporation into fusicoccins J and A through (+)-fusicocca-2,10(14)-dien-8β-ol, whose occurrence in the mycelial extract has been confirmed by direct comparison of its 1H NMR and GC–MS data with those of the synthetic sample, proving the early biosynthetic route leading to the aglycons of fusicoccins.

High-pressure Diels–Alder reaction of [60] fullerene with several tropones. Characterization of the 1 : 1-cycloadducts

The high-pressure Diels–Alder reaction of fullerite with tropone and several of its derivatives under 300 MPa gave 1 : 1-[4 + 2] cycloadducts of C60 in good yields. Their 1H and 13C NMR spectra were consistent with the structures depicted. These compounds quantitatively regenerate starting materials upon thermolysis.

(+)-Menthol and Its Hydroxy Derivatives, Novel Fungal Monoterpenols from the Fusicoccin-producing Fungi, Phomopsis amygdali F6a and Niigata 2

In our search for new fusicoccins of unique diterpene glucosides from Phomopsis amygdali, we found that a fragrant substance was formed in the early stage of fusicoccin fermentation. This fragrant constituent was isolated and identified as (+)-menthol, which is a novel fungal metabolite as the enantiomer of well-known peppermint (−)-menthol. (+)-7-Hydroxymenthol and new (+)-(6S)-hydroxymenthol were also isolated and identified as fungal metabolites. In addition, p-menthanetriol, which has been reported as the first fungal monoterpene from the fungus, was also isolated. The possible biosynthetic relationship of these metabolites is discussed.

Revisit to the reduction of allylic chlorides to less substituted olefins by a low-valent chromium species in the presence of a proton source

Abstract Allylic chlorides have been reduced to afford less substituted olefins by a low-valent chromium species in the presence of an alcoholic proton source. This process certainly has synthetic benefits since the regio-selectivity of the reduction is high and the reaction conditions are mild and nearly neutral.