Masaharu Kojima

Palladium-catalyzed carbonylative cross-coupling of organoboranes with aryl iodides or benzyl halides in the presence of bis(acetylacetonato)zinc(II)

Abstract Carbonylative cross-coupling reactions of organoboranes with aryl iodides and benzyl halides successfully catalyzed by dichlorobis(triphenylphosphine)palladium(II) in the presence of bis(acetylacetonato)zinc(II) produce unsymmetrical ketones in reasonable yields.

Metabolic pathway of 2-deoxy-2-fluoro-D-glucose studied by F-19 NMR

The behavior of 2-deoxy-2-fluoro-D-glucose (FDG) in mouse has been studied by F-19 NMR method for long period. The F-19 NMR signals of FDG or its metabolites were observed in tissues without serious broadening. FDG was found to be accumulated in organs in the form of FDG or FDG-6-phosphate and 2-deoxy-2-fluoro-D-mannose (FDM) or FDM-6-phosphate, and the latter dominated the former in the heart sampled at 24 hr or later. The fluorine compounds were excreted in urine in both forms. The clearance was rapid from brain, liver, and blood, but was slow from heart.

Carbonylative cross-coupling reaction of aryl iodides with alkylaluminums by palladium complex catalysis

Abstract Secondary and/or tertiary alcohols and unsymmetrical ketones have been obtained in moderate to good yields by the palladium-catalyzed (5 mol%) carbonylative coupling of aryl iodides with alkylaluminum compounds under very mild conditions (20–50°C, 1 atm of carbon monoxide). The type of the reaction product depended on the aluminum reagent employed. While the selective formation of secondary alcohols was observed in the reaction with i-Bu 3 Al, the use of Et 3 Al led to a mixture of a ketone and two alcoholic products. With Et 2 AlCl predominantly unsymmetrical ketones were produced. In all cases, formation of directly cross-coupled products was not observed. DME and benzene can be used as solvents, but THF is unsuitable. Nickel catalysts were found to be ineffective for this reaction.

The dimethylsulfonium moiety as a leaving group in aromatic radiofluorination using tetra-n-butylammonium [18F]fluoride

The reaction of aryldimethylsulfonium methylsulfates with tetra-n-butylammonium [18F]fluoride in acetonitrile or dimethyl sulfoxide has been studied. Fluorine-18 incorporation into the aromatic ring of the selected aryldimethylsulfonium salts was observed, depending greatly on the substituent group on the aromatic ring. It was found that the displacement yields with the p-nitro- and o-nitro-substituted substrates are consistently greater using a polymethylpentene vessel than those using a Pyrex vessel. The nucleophilic displacement of the dimethylsulfonium group was not a good general method for labeling aromatic compounds with 18F, because of the facile demethylation of the sulfonium salt by a nucleophile present.

Synthesis of daunosamine

Abstract The rearrangement of methyl 3-azido-2- S -benzyl-3-deoxy-2-thio-α- D -altropyranoside ( 3 ) in methanol to give methyl 3-azido-2- S -benzyl-3-deoxy-2-thio-αβ- D -altrofuranoside ( 4a ) was catalysed by Amberlite CG-120(H + ) resin. Partial benzoylation of 4a gave the 6- O -benzoyl derivative ( 4b ), the 5- O -toluene- p -sulphonyl derivative ( 4c ) of which was converted into methyl 5,6-anhydro-3-azido-2- S -benzyl-3-deoxy-2-thio-αβ- L -galactofuranoside ( 7 ) with methanolic sodium methoxide. Reduction of 7 with lithium aluminium hydride gave the 3,6-dideoxy sugar ( 8a ) which, with Raney nickel, gave methyl 3-amino-2,3,6-trideoxy-αβ- L - lyxo -hexofuranoside ( 9 ). Acid hydrolysis of 9 gave 3-amino-2,3,6-trideoxy- L - lyxo -hexose (daunosamine) which is a component of the antibiotic daunomycin.

Bromofluorination of double bonds using N-bromoimides and tetra-N-butylammonium fluoride as a source of floride

Abstract Bromofluorination of 4- tert -butyl-1-methylcyclohexene ( I ) using a combination of N-bromosuccinimide and tetra- n -butyl- ammonium fluoride as a source of fluoride gave the vicinal bromofluorides in acceptable yield. Similar treatment of methyl 3α, 7α-diacetoxy-5β-chol-11-ene-24-carboxylate ( IV ) afforded the 12α-bromo-11β-fluoro steroid ( V ) in good yield.

Syntheses OF 15α- and 15β-carboxymethyltestosterone bovine serum albumin conjugates: Characteristics of the antisera to testosterone

Abstract Syntheses of 15α- and 15β-carboxymethyltestosterone (15α- and 15β-CMT) were investigated in order to prepare testosterone-bovine serum albumin conjugates for radioimmunoassays of testosterone. A mixture of 15α- and 15β-bis (ethoxycarbonyl)methyl-3β-hydroxy-5-androsten-17-one (IIa and IIb) obtained by a reaction of 3β-hydroxy-5,15-androsta-dien-17-one (I) and sodium diethyl malonate was oxidized to afford a mixture of 15α- and 15β-bis(ethoxycarbonyl)methyl-4-androstene-3, 17-dione (Va and Vb). After the separation by silica gel chromatography, each epimer obtained was hydrolyzed by acid, followed by decarboxylation, and selective reduction of the 17-ketone to give 15α- and 15β-CMT. The antisera, generated in rabbits by immunization with the bovine serum albumin (BSA) conjugates of 15α- and 15β-CMT, respectively, exhibited high specificity for testosterone.

Homoallylic rearrangement of 19-iodocholest-5-en-3β-ol: New adrenal scanning agent

Homoallylic rearrangement of 19-iodocholest-5-en-3β-ol (II) gave 6β-iodomethyl-19-norcholest-5(10)-en-3β-ol (III). It was proved that the preparation of (II) according to the method of Counsell et al. previously reported usually contains (III) as a by-product.

N,N-disubstituted lithium bis(carbamoyl)cuprate. A convenient complex for one-pot conversions of amines to formamides, oxamides, carbamates, and oxamic acids

Abstract Lithium bis(carbamoyl)cuprates (2) were readily derived from secondary amines such as N-methylaniline, N-methylbenzylamine, and diethylamine, under mild carbonylation conditions (0°C, 1 atm of carbon monoxide), but diphenylamine and benzylphenylamine were unsuitable as the starting materials. The carbamoylcopper complexes 2 formed in ether were readily converted to the corresponding formamides, oxamides, carbamates, and oxamic acids by the appropriate treatment. The formation and stability of 2 depended much on the solvent used. The higher polarity effect of the solvent (DME, THF, and HMPA) made 2 less stable and caused concomitant evolution of carbon monoxide in further reactions. A palladium catalyst was found to be effective for cross-coupling reactions of 2 with iodobenzene or (E)-β-bromostyrene.

Mechanism of the pyranoside → furanoside isomerization in the acid-catalysed methanolyses of some methyl hexopyranosides

Abstract On treatment with Amberlite CG-120(H +1 ) resin in methanol- d 4 , methyl 2,3-dideoxy-2,3-epithio-α- D -allopyranoside (1a) gave trideuteromethyl 2,3-dideoxy-2,3-epithio-β- D -allofuranoside (4b) , methyl 2- S -benzyl-2-thio-α- D -altropyranoside (10) gave methyl 2- S -benzyl-2-thio-α-(and β)- D -altrofuranoside (11 and 12) . 3- S -benzyl-3-thio-α- D -altropyranoside (14) was unaffected, and methyl 2-deoxy-α- D - ribo -hexopyranoside (17) , methyl 2- O -methyl-α- D -altropyranoside (20) , and methyl 2-deoxy-2-iodo-α- D -altropyranoside (23) isomerized to the corresponding methyl furanosides. The pyranoside → furanoside isomerization is explained by a mechanism involving cyclic cation intermediates B 1 and B 2 ), the inductive effect of the substituent at C-2, and the steric effect of substituents at C-2 and C-3.