Kikumasa Sato

A practical synthesis of (+-)-phosphinothricine

Abstract A practical synthesis of (±)-phosphinothricide from trimethyl phosphite is described.

A new synthesis of vitamin K viaπ-allyinickel intermediates

A new synthesis of vitamins K1(1), and K2(5n)(2) is described. Reaction of bis-(1–3-η-3-alkylbut-2-enyl)di-µ-bromodinickel complexes (8a–c) with 2-bromo-3-methylnaphthalene-1,4-diyl bis(methoxymethyl) ether (6a) or diacetate (6b) in a polar, co-ordinating solvent gave the corresponding vitamin K derivatives (9a–d) in high yield, which were converted into vitamin K analogues also in high yield. The stereoselectivity decreases as the donor strength of the solvent increases. All-trans-vitamin K2(45)(2b) was isolated from the trans–cis-mixture (70:30) prepared by this method.

Stereoselective total synthesis of (S)-(–)-dolichol-20

A stereoselective synthesis of (S)-(–)-dolichol-20 (1a) was achieved using (Z,Z,Z,Z,Z,Z,Z,Z,E,E)-undercaprenol (11), the C20 block (5), and the optically active C25 block (3) as the key building blocks.

Selective synthesis of monomethyltocols viaη-allylnickel complexes

A new synthesis of the monomethyltocols (1a–c) and the 2,2-dimethylchroman-6-ol models (2a–c), using the di-µ-bromobis-(1–3-η-3-alkylbut-2-enylnickel) complexes (9a and b), is described. Reaction of the η-allyl-nickel complexes (9a and b) with the bromo-p-diacetoxytoluenes (3a–c) gave the corresponding alkyl substituted p-diacetoxytoluenes (10a–c) and (11a–c) in high yield, and these were converted into the chromanols (1a–c) and (2a–c) by hydrolysis–cyclisation with tin(II) chloride and hydrochloric acid, also in high yield.

Synthesis of 4-, 5-, 6- and 7-Substituted N-Tosylindoles from Substituted Anilines

4-, 5-, 6-, and 7-Substituted N-tosylindoles are prepared from N-tosylanilides, carrying 2-acetoxy-1-(isopropylthio)ethyl group at the ortho position, which can be prepared from substituted anilines and dialkyl sulfide by [2,3] sigmatropic rearrangement

An efficient stereoselective synthesis of co-enzyme Q10

Co-enzyme Q10 was efficiently synthesised by stereo-and regio-selective prenylation of the protected hydroquinone (2) with isoprene epoxide and solanesyl p-tolyl sulphone in good overall yield.

Stereoselective synthesis of solanesol and all-trans-decaprenol

Allylic p-tolyl sulphones (5), (14), and (16) couple with allylic bromide (7) and geranyl bromide to produce regio- and stereo-chemically pure 1,5-diene systems. The coupling of all-trans-ω-bromogeranyl acetate (7) with geranyl p-tolyl sulphone (5) and higher isoprenologues (21), (24), and (27), followed by reductive elimination of p-tolysulphonyl group, furnishes a stereoselective synthesis of all-trans-polyprenols (3), (23),(26), and decaprenol (1b). Solanesol (1a) was synthesised using trans-4-chloroprenyl acetate (29) instead of (7).

Synthesis and reaction of 3-hydroxytetrahydro-4H-pyran-4-one

Photosensitized oxygenation of 5,6-dihydro-4-methyl-2H-pyran (1) in methanol followed by reduction gave two kinds of allyl alcohols [(2) and (3)] together with the epoxy-ethers (4) and (5). When the reaction was carried out in solvents other than alcohols it gave (2) and (3) exclusively. Ozonization of 4-methylenepyrans (2) and (13) followed by reduction with zinc powder–acetic acid afforded 3-hydroxytetrahydropyrans (11) and (14). Bromination of (14) gave the dibromide (16), which yielded bromopyran (17) and 3-acetoxy-4H-pyran-4-one (18) on treatment with 1,8-diazabicyclo[5.4.0]undecene. However, the reaction of (16) with silver acetate in acetic acid predominantly afforded (17) in excellent yield. Other allied reactions and mechanisms of these reactions are described.

Reactions of αα′-dibromocycloalkanones with bases

Reactions of αα′-dibromocycloalkanones [(1) and (2)] with various bases in several solvents have been studied. Treatment of 2,5-dibromocyclopentanone (1) with bases such as sodium hydrogen carbonate, sodium acetate, sodium phenoxide, and secondary amines afforded the corresponding 2-substituted cyclopent-2-enones [(3), (4), (5), and (8)]. Similar treatment of 2,6-dibromocyclohexanone (2) with weak nucleophilic bases gave 2-substituted cyclohex-2-enones (9) and (10), but reactions with secondary amines possessing both strong basicity and high nucleophilicity gave 2-aminocyclohex-2-enones (13a–c) and cyclopent-1-enecarboxamides (14a–c). The ratio of (13) to (14) is strikingly affected by the reaction solvent: (13) or (14) was obtained selectively when hexamethylphosphoramide or chloroform was used, respectively. Allied reactions are described and mechanisms are suggested.

Stereospecific synthesis of (Z,Z,Z,Z,Z,Z,Z,Z,E,E)-undecaprenol (bacterialprenol) using an all-cis-diterpene building block

Base-induced coupling of two monoterpene building blocks (6) and (7) followed by functional group transformations afforded an all-cis-diterpene building block (4), which was used to effect C20 homologation of (E,E)-farnesol and (Z,Z,Z,Z,E,E)-heptaprenol (betulaprenol-7)(9)via the corresponding p-tolyl sulphones; thus the title undecaprenol (1) was synthesised stereospecifically in short steps.