Tsuyoshi Shishibori

Intramolecular hydrogen bonding in hydroxy-keto-steroids

The i.r. spectra of hydroxy-keto-steroids with an equatorial-hydroxy-group α to the ketone show a band due to hydrogen bonding (OH ⋯ O type); those with an axial hydroxy-group α or β to the ketone exhibit two absorption bands, due to a free and a bonded hydroxy-group (OH ⋯π type). The mode of multiple hydrogen bonding in epimeric pairs of monohydroxy-diketo-steroids and dihydroxy-monoketo-steroids is discussed. Hydrogen bonding in dihydroxy-keto-steroids is more extensive than in monohydroxy-keto-steroids.

The stereospecificity of biosynthesis of squalene and β-amyrin in Pisum sativum

Abstract The distribution of deuterium in squalene and β-amyrin, biosynthesized from mevalonic acid-6,6,6- d 3 in Pisum sativum , has been examined b

Interconversion and cyclization of acyclic allylic pyrophosphates in the biosynthesis of cyclic monoterpenoids in higher plants

Abstract The biosynthesis of cyclic monoterpenoids has been investigated in both intact plants and cell-free extracts of several higher plants. The participation of a non-redox process in the biosynthesis of the cyclic monoterpenoids was indicated by the retention of all the tritium labels originating from [2- 14 C,5- 3 H 2 ]mevalonic acid and [1- 14 C,1- 3 H 2 ]geranyl, neryl and linalyl pyrophosphates. The cell-free extract catalysed the non-redox interconversions of geranyl, neryl and linalyl pyrophosphates to each other. By contrast, in both intact plants and cell-free extracts, the incorporation of linalyl pyrophosphate into the cyclic monoterpenoids occurred preferentially to the incorporation of neryl and geranyl pyrophosphates. These observations suggest the involvement of a tertiary allylic compound and/or its equivalent as a key intermediate, not only in the interconversion of the acyclic allylic pyrophosphates, but also in the formation of the cyclic monoterpenoids.

Structure and biosynthesis of malloprenols from Mallotus japonicus

Abstract The mallo prenol isolated from the leaves of Mallotus japonicus was elucidated to be a mixture of (2Z,6Z, 10Z, 14Z, 18Z, 22Z, 26E, 30E, 34E)-3,7,11,15,19,23,27,31,35,39-decamethyl-2,6,10,14,18,22,26,30,34,38-tetracontadecaen-1-ol and its C45- and C55-homologues and not the previously reported structure. The malloprenols were demonstrated to be biosynthesized by successive cis condensation of isoprene residues with (2E, 6E, 10E)-geranylgeranyl pyrophosphate.

Structure and biosynthesis of cleomeprenols from the leaves of Cleome spinosa

Cleomeprenols isolated from Cleome spinosa L. (Capparidaceae) have been identified as nonaprenol (1), decaprenol (2), and undecaprenol (3), which are composed of an ω-terminal isoprene, three internal E-isoprene, and the remaining Z-isoprene residues, respectively. Feeding experiments using stereospecifically double-labelled radioactive mevalonate showed that all the cleomeprenols are composed of four biogenetically E- and the remaining biogenetically Z-isoprene residues. Occurrence of the successive cis-condensation of isoprene residues with (2E, 6E,10E)-geranylgeranyl pyrophosphate was demonstrated by comparing the incorporation of a homologue of all-E-prenyl pyrophosphates with that of the corresponding 2Z-isomer.

Biosynthesis of linalool in higher plants

Abstract The labelling pattern of linalool biosynthesized from [2- 14 C]mevalonic acid by Cinnamomum camphora was consistent with the pathway shown in the scheme. The activities at C-4 and C-8 (and/or C-10) were nearly equal, in opposition to the results 1,2 observed for the bicyclic terpene compounds.

Preferential participation of linaloyl pyrophosphate rather than neryl pyrophosphate in biosynthesis of cyclic monoterpenoids in higher plants

Comparisons of the incorporation of [1-3H2]nerol, [1-3H2]geraniol, and [1-3H2]linalool and their pyrophosphates into some cyclic monoterpenoids have been made in both intact plants and cell-free systems; the preferential incorporation of linalool and its pyrophosphate into the cyclic monoterpenoids suggests that they are better precursors than nerol or its pyrophosphate for the biological formation of the cyclic monoterpenoids.

Conformational energy of (+)-pulegone

Temperature-dependent circular dichrosim measurements on (+)-pulegone enabled us to estimate its conformational energy.