Jun-ichi Minamikawa

Doebner–Miller synthesis in a two-phase system: practical preparation of quinolines

Abstract Doebner–Miller cyclization was carried out in a two-phase solvent system. The method has shown to be advantageous to the yield and to the ease of the work-up process.

Catalytic asymmetric oxidation of sulfide with titanium–mandelic acid complex: practical synthesis of (S)-3-[1-(2-methylphenyl)imidazol-2-ylsulfinyl]propan-1-ol, the key intermediate of OPC-29030

Abstract An effective catalytic asymmetric oxidation of prochiral sulfide 1a to (S)-2a has been achieved by the use of chiral titanium–mandelic acid complex. The enantioselectivity was found to be not influenced by moisture, and moderate to high selectivity (76% ee) was obtained at room temperature (25°C). Thus a practical synthetic method for the platelet adhesion inhibitor, OPC-29030, was established utilising asymmetric oxidation of 1a.

Interesting reaction of the indanone oximes under Beckmann rearrangement conditions

Attempted Beckmann rearrangement of the 6-methoxyindanone oximes in conventional conditions resulted in the formation of the two kinds of unexpected products: 2-sulfonyloxyindanone and the dimeric product. Related rearrangement was also observed in the reaction with RhCl-trifluoromethansulfonic acid system.

A convenient one pot asymmetric synthesis of cis-β-lactams: Key precursors for optically active 2-oxaisocephems

Abstract Asymmetric annelation of the disilylated imine 3 generated in situ from D-threonine 2 with arid chlorides 4 and triethylamine followed by esterificadon provided cis-β-lactams 5 and 6 in excellent yields with high diastereoselectivity under mild conditions. And conversion of compounds 5 into 15 , derivatives of 2-oxaisocephems having a thio-subsdtuted methyl group at the 3-position and a 2-aminothiazol-4-yl moiety at the 7-position, is described. Biological activities of the new compounds are presented. In particular, 15b showed potent antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA) and Enterococcus faecalis which cause a serious clinical problem in antibacterial chemotherapy.

Glycosylation of sialyl acetates with a novel catalyst combination: Bismuth triflate and BF3·OEt2 system

A combined system of bismuth triflate [Bi(OTf)(3)] and boron trifluoride etherate (BF(3).OEt(2)) in dichloromethane is an efficient promoter for the glycosylation of N-acetylneuraminic acid derivatives. The co-existence of two acid catalysts such as Bi(OTf)(3)-BF(3).OEt(2) or Bi(OTf)(3)-PPA is confirmed to be essential for obtaining high yields of glycosylation products with p-nitrobenzyl alcohol, which also turned to be superior to those reported previously.

Beneficial effect of cesium salts on Pd-catalyzed hydroxycarbonylation.

A Pd(0)-catalyzed hydroxycarbonylation of the aryl bromide was effectively carried out in the presence of some Cs salts such as cesium carbonate, cesium bicarbonate, and cesium acetate in wet DMF solution. For the understanding of their function, an oxy-coordinated intermediate arising from a Cs oxygen-Pd interaction has been postulated, which is likely to be responsible for related Cs assisted catalytic processes.

Facile Conversion of Arenediazonium Salts to the Corresponding Fluoroarenes Using Boron Trifluoride Diethyl Ether Complex

Abstract The conversion of various arenediazonium salts 1 to the corresponding fluoroarenes 2 has been achieved in good yields under mild conditions in boron trifluoride diethyl ether complex.

Practical asymmetric oxidation of 3-[1-(2-methylphenyl) imidazol-2-ylthio]propan-1-ol based on a titanium-mandelic acid complex

Abstract A practical and effective asymmetric oxidation of prochiral sulfide 1 to (S)- 2 has been described. The enantioselectivity was not found to be influenced by moisture and moderate to high selectivity was obtained at room temperature (25 °C).

Asymmetric synthesis of a xanthine dehydrogenase inhibitor (S)-(−)-BOF-4272: Utility of chiral alkoxysulfonium salts

Abstract A practical synthetic method for a xanthine dehydrogenase inhibitor, ( S )-(−)-BOF-4272, was established utilizing an asymmetric oxidation of diaryl sulfide BOF-4269. The oxidation of the sulfide with 1-chlorobenzotriazole carried out in the presence of 4-cyanopyridine and chiral 2-phenylcyclohexanol gave a high enantiomeric excess (73% ee ). The sulfoxides in each enantiomerically pure form could be obtained by treating with alkaline hydrolysis or thermolysis of one the diastereomeric intermediate sulfonium salts (>99% de ). Thus the transformation into the sulfoxides occur with virtually perfect inversion (alkaline hydrolysis) or retention (thermolysis). It is therefore possible to obtain the target sulfoxide, ( S )-(−)-BOF-4272, from both the two diastereomeric sulfonium intermediates.

A practical synthesis of 3,4-diethoxybenzthioamide based on Friedel-Crafts reaction with potassium thiocyanate in methanesulfonic acid.

The synthesis of 3,4-diethoxybenzthioamide, the key intermediate for OPC-6535, is achieved by employing Friedel-Crafts reaction of 1,2-diethoxybenzene with potassium thiocyanate in methanesulfonic acid at ambient temperature.