Takashi Tokoroyama

Biarylheptanoids and other constituents from wood of Alnus japonica

Abstract The wood of Alnus japonica has been shown to contain a number of biarylheptanoids as well as other phenolics, including secoisolariciresinol diferulate. The co-occurrence of cyclized biarylheptanoids with their corresponding acyclic biarylheptanoids has been demonstrated and this fact may have biosynthetic significance. The possible chemotaxonomic importance of biarylheptanoids in members of the Betulaceae is discussed. The isolation and identification of several steroids and triterpenoids are also described.

Total synthesis of (±)-ageline a, a physiologically active constituent ofAgelas sponges

Abstract The monocyclic diterpene moiety of ageline A ( 1 ) was convergently constructed by the palladium-mediated coupling of C 9 -terpenic chain as vinyl bromide 10 and C 11 -monocyclic segment as alkylzinc compound 16 , which was obtained through a stereoselective cyclization and associated transformations. The appendage of 9-methyladenine ring to the diterpene unit led to the total synthesis of (+)-ageline A.

Remarkable stereocontrol observed in the ring formation by intramolecular hosomi-sakurai reaction

Abstract The cyclization of 2-(3′,4′-dimethyl6′-trimethylsilyl-4′-hexenyl)-2-cyclohexenone with TiCl 4 , afforded stereospecifically 6α,7α-dimethyl-6β-vinyl-5βH-1-decalone derivative and the two-fold diastereoselection involved is reasoned in terms of orientation control and folding strain control.

One-pot stereospecific construction of cis-clerodane skeleton by means of doubly stereocontrolled cyclization: Total synthesis of linaridial

Doubly stereocontrolled cyclization of the allylsilane derivative 1 followed by trapping of the enolate with ClCH2SMe gives in one-pot manner the decalone derivatve 5 in which all of the four contiguous diastereomeric centers of cis-clerodane skeleton have been secured. The total synthesis of linaridial 4 have been accomplished from 5.

Asymmetric synthesis of clerodane diterpenoids: total synthesis of (–)-methyl kolavenate

The asymmetric synthesis of (8R,9S,10R)-4,8,9-trimethyl-9-vinyl-Δ4-3-octalone, a versatile intermediate for the syntheses of both trans- and cis-neo-clerodane diterpenoids, has been achieved by extension of Enders asymmetric alkylation, and its utility is exemplified by the total synthesis of (–)-methyl kolavenate, the first example of a clerodane diterpenoid in optically active form.

Unusual reaction of 2-trimethylsilylethylidenetriarylphosphoranes (seyferth-wittig reagent) with α-methylaldehydes: a novel method for highly cram-diastereoselective addition of vinyl anion equivalent

Abstract By the reaction of α-methylaldehydes with trimethylsilylethylidenetriarylphosphoranes the introduction of vinyl group is effected in highly Cram-selective manner.

The structure and absolute configuration of syringopicroside: A new iridoid glucoside from Syringa vulgaris L.

Abstract The structure elucidation of syringopicroside, a new iridoid glucoside from Syringa vulgaris L., is described.

A general method for the synthesis of clerodane diterpenoids. Stereospecific total syntheses of (±)-15, 16-epoxy-cis-cleroda-3, 13(16), 14-triene and (±)-maingayic acid12

Abstract A general method for the syntheses of cis - and trans -clerodane diterpenoids has been developed and its applications to the total syntheses of both representatives 11 and maingayic acid (32) in racemic forms are described. The common Δ4-3-octalone intermediates 2a and 2b were prepared from 3,4-dimethyl-2-cyclohexenone by a stereospecific conjugate addition-alkylation sequence and the subsequent thermodynamically controlled annelation. The dimethylcuprate addition to 2a followed by enolate trapping afforded stereospecifically the cis -alcohol 12, from which (±)-11 has been synthesized. On the other hand hydrocyanation of 2b gave trans -intermediate 33, and then it has been converted to (±)-maingayic acid (32).

Efficient stereoselective syntheses of both (×)-juvabione and (×)-epi-juvabione by new extracyclic stereocontrol methodology

Abstract The Hosomi-Sakurai reactions of E- and Z-crotylsilanes with cyclohexenone at −78 °C showed respectively high erythro and relatively low threo selectivities, modification of the silyl substituents giving a variable effect. In the reaction with Z-alkoxycrotylsilanes, the threo selectivity could be improved by the utilization of the kinetic difference between the diastereomeric products 4 and 5 to the secondary cyclization. Starting from 4 and 4 thus obtained, the syntheses of both (±)-juvabione and (±)-epi-juvabione have been respectively achieved in a concise way.

Carbonyl addition reaction by means of β-silylphosphorous ylide. Anti-diastereoselective vinylation of α-alkoxy aldehydes.

Abstract β-Silylphosphorous ylide 1c reacts with α-alkoxy aldehydes 2 to give exclusively vinylation product 3 , with high anti -diastereoselectivity.