Junzo Nokami

A new synthetic method for γ-butyrolactols by the paladium-catalyzed regioselective oxidation of 1-alken-4-ols

Abstract 3-Substituted 1-alken-4-ols were oxidized with PdCl 2 -benzoquinone regioselectively at the terminal carbon to afford cyclic hemiacetals (γ-butyrolactols), which were converted to γ-butyrolactones by the Jones oxidation. This reaction was applied to the syntheses of optically active deoxyribose and γ-butenolides.

A new chiral disulfonamide ligand derived from α-amino acid for catalytic enantioselective cyclopropanation

Abstract A new disulfonamide prepared from α-amino acid in five steps catalyzed cyclopropanation of allylic alcohols with Et 2 Zn and CH 2 I 2 to afford the corresponding cyclopropylmethanols in moderate to good enantioselectivites. In particular, the reaction of cinnamyl alcohol in the presence of a chiral disulfonamide 1 k afforded an excellent enantioselectivity (85% ee).

Regioselective ring opening of benzylidene acetal protecting group(s) of hexopyranoside derivatives by DIBAL-H.

The reductive ring-opening reaction of benzylidene-protected glucosides and mannosides such as methyl 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-d-glucoside (1) and methyl 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-d-mannoside (4) by using a toluene stock solution of DIBAL-H and a dichloromethane stock solution of DIBAL-H gives mainly or selectively the corresponding 2,3,4-tri-O-benzyl derivatives (2, 5) and 2,3,6-tri-O-benzyl derivatives (3, 6), respectively, although that of methyl 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-d-galactoside (7) gives methyl 2,3,6-tri-O-benzyl-alpha-d-galactoside (9) selectively irrespective of the solvent of the stock solution of DIBAL-H. Similarly, the reaction of the exo-isomer of methyl 2,3:4,6-di-O-benzylidene-alpha-d-mannopyranosides (exo-10) with a toluene stock solution and dichloromethane stock solutions of DIBAL-H selectively gives methyl 3-O-benzyl-4,6-O-benzylidene-alpha-d-mannoside (12) and methyl 2-O-benzyl-4,6-O-benzylidene-alpha-d-mannoside (11), respectively, although that of endo-10 selectively affords 11, irrespective of the solvent of the stock solution of DIBAL-H.

New route to α-adducts of homoallylic alcohols by an acid-catalyzed stereospecific allyl-transfer reaction from γ-adducts

Allylation of aldehydes by an allyl-transfer reaction from the gamma-adducts of homoallylic alcohols has been successfully carried out to give the corresponding alpha-adducts regiospecifically. The reaction proceeds via a hemiacetal (11), derived from an aldehyde and the homoallylic alcohol, followed by a six-membered cyclic transition state (2-oxonia[3.3]-sigmatropic rearrangement) in the presence of a Lewis acid. Moreover, the gamma-adducts are restructured into the corresponding alpha-adducts via a similar transition state by an acid catalyst, in which chirality in both anti- and syn-gamma-adducts is stereospecifically transferred to the corresponding E- and Z-alpha-adducts, respectively, with > 98% ee.

FACILE SYNTHESIS OF (+)-BREFELDIN A

Abstract (+)-Brefeldin A (1) was synthesized by using (+)-4-cyanomethylcyclopent-2-en-1-one (2) as a key compound. 4-Hydroxy-2-enoate functionality was built by the reaction of the aldehyde (7) with (S)-ethyl p-chlorophenylsulfinylacetate.

Preparation of 4-hydroxy-2-alkenenitriles from phrnylsulfinylacetonitrile with keetones or aldehydes, and its synthetic application to substituted furans

Abstract The reaction of phenylsulfinylacetonitrile 1 with ketones or aldehydes gave 4-hydroxy-2-alkenenitriles which were converted to 2- and/or 3-substituted furans by the treatment with diisobutylaluminumhydride(DIBAL) followed by acid hydrolysis.

A new total synthesis of dl-sirenin

Abstract A new total synthesis of dl-sirenin ( 1 has been effectively accomplished by employing the acetate 4a obtained by the stereoselective rearrangement of the acetate 3 using a palladium catalyst.

Preparation of methyl 1,3-dien-2-carboxylate by the palladium-catalyzed carbonylation of 2,3-dien-1-ols

Abstract Palladium-catalyzed carbonylation of methyl carbonates of 1,2-disubstituted 2,3-dien-1-ols (α-allenylic alcohols) proceeds at a room temperature under atmospheric pressure of carbon monoxide to afford 3,4-disubstituted 1,3-dien-2-carboxylates regioselectively in good yields.

Facile formation of 4-hydroxyalk-2-enone functionality

Reaction of aldehyde with 1-(phenylsulfinyl)alkan-2-one (1), in the presence of diethylamine (and acetic acid) in acetonitrile at 60 °C, gave 4-hydroxyalk-2-enone derivative in good yield.

Syntheses of PGJ2 type analogues: 16-hydroxy-11-oxo-Δ5,9,12,14-prostatetraenoic acid t-butyl ester and its related derivatives

PGJ2 analogues, the title compound (8c) and its related derivatives (8a, 8b), were synthesized via the three-component coupling process involving 1,4-addition reaction of phenylsulfinylallylic carbanion (2′) to cyclopentenone derivative (1) followed by trapping the generated enolate with aldehyde (3).