[show abstract][hide abstract] ABSTRACT: An efficient three component one-pot synthesis of N-silylated α-aminophosphonates and α,α-disubstituted α-aminophosphonates was developed using Yb(OTf)3 as a catalyst at room temperature under mild conditions.
[show abstract][hide abstract] ABSTRACT: A green, solvent-free protocol was developed for the radical-mediated intramolecular cyclization of haloacetals and the deoxygenation of S-methyl dithiocarbonates and cyclic thionocarbonate. This process uses tributyl methyl ammonium hypophosphite as a H-donor in the presence of triethylborane or t-butyl peroxide. This methodology provides eco-friendly reaction conditions.
[show abstract][hide abstract] ABSTRACT: A synthetic method for 2',3'-dideoxyinosine (ddI) from inosine was established via radical deoxygenation of N1,5'-O-diprotected-2',3'-bis-S-methyl dithiocarbonate of inosine derivatives. The radical deoxygenation proceeded smoothly to give the desired dideoxy compounds in good yields using 1-ethylpiperidinium hypophosphite and triethylborane. Benzyl or p-methoxybenzyl protection of inosine at the N1, 5'-O-positions were effective for the ddI synthesis.
[show abstract][hide abstract] ABSTRACT: An enantioselective addition of alkyl radicals to glyoxylate oxime ether mediated by Cinchona alkaloid derived chiral ammonium salts of hypophosphorous acid, QP and QDP, has been developed.
Chemical Communications 01/2007; · 6.38 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Friedel–Crafts acylation of activated benzenes with various aromatic and aliphatic acid chlorides was studied in the presence of indium metal. The reaction was accomplished in high isolated yields under solvent or solvent-less conditions. The method is also applicable for preparing diaryl sulfones from aromatic compounds and aryl sulfonyl chlorides.
Tetrahedron Letters - TETRAHEDRON LETT. 01/2006; 47(34):6063-6066.
[show abstract][hide abstract] ABSTRACT: An efficient and mild method is developed for radical deoxygenation of alcohols and formation of carbon–carbon bonds in water without adding additives such as surfactants. The reaction was applied to synthesis of 2′,3′-didehydro-2′,3′-dideoxynucleosides that are potent anti-HIV agents. The reaction afforded environmentally benign reaction conditions.
Tetrahedron Letters - TETRAHEDRON LETT. 01/2005; 46(11):1799-1802.
[show abstract][hide abstract] ABSTRACT: Indium-mediated coupling reactions of acyl chlorides and amines for the synthesis of amide bonds are described. The reaction afforded high yields of the desired amides under mild and neutral conditions, and it was applicable also to the preparation of peptides without epimerization.
[show abstract][hide abstract] ABSTRACT: Trifluoroacetates of tertiary alcohols undergo deoxygenation by Ph2SiH2 in the presence of (tBuO)2 in excellent yields of the deoxy products without affecting the stereochemistry at β-carbon.
Tetrahedron Letters - TETRAHEDRON LETT. 01/2004; 45(15):3031-3033.
[show abstract][hide abstract] ABSTRACT: Utilizing three biocompatible components, a series of novel cationic lipids has been chemically synthesized and tested for their gene-transferring capabilities in 293 transformed kidney cells and B16BL6 mouse melanoma cells. The synthesized cationic lipids consisting of a core of lysine and aspartic acid with hydrocarbon chains of varied length were assigned the acronyms DLKD (O,O'-dilauryl N-lysylaspartate), DMKD (O,O'-dimyristyl N-lysylaspartate), DPKD (O,O'-dipalmityl N-lysylaspartate), and DSKD (O,O'-distearyl N-lysylaspartate). The gene-transferring capabilities of these cationic lipids were found to be dependent on the hydrocarbon chain length. Under similar experimental conditions, the order of gene transfection efficiency was DMKD > DLKD > DPKD > DSKD. Addition of cholesterol or dioleoyl phosphatidylethanolamine (DOPE) as a colipid did not change this order. Colipid addition affected the transfection efficiency positively or negatively depending on the length of the cationic lipid acyl chain. On the whole, the length of the hydrophobic carbon chain was a major factor governing the gene-transferring capabilities of this series of cationic lipids. The observed differences in transfection efficiency may be due to differing binding affinities to DNA molecules as well as differences in the surface charge potential of the liposome-DNA complexes (lipoplexes) in the aqueous environment.
[show abstract][hide abstract] ABSTRACT: A convenient one-pot process for preparing various esters from carboxylic acids using the Ph3P-CCl3CN has been developed. Racemic α-tocopherol, clofibrate and flavoxate were prepared in high yields using this method.
[show abstract][hide abstract] ABSTRACT: tions for the acylation of alcohols with acyl chlorides in the presence of indium. The results are summarized in Table 1. Reaction of 2 (1 equiv) with 1 (1 equiv) in the presence of indium (1 equiv) in CH3CN at room temperature produced the corresponding ester in only 21% yield and the starting acyl chloride and alcohol were recovered. The optimal yield of the ester was attained with 3 equiv of 1 or 2 in the presence of 3 equiv of indium. The solvent effect of acylation of 2 with 1 in the presence of indium was studied. The reaction proceeded efficiently in common organic solvents such as DMF, Et2O, THF or CH2Cl2 whereas non-polar solvents such as n-hexane or benzene gave poor yields of the ester. The reactivity of acyl halides was studied. The results are presented in Table 2. The results show that aromatic acyl chlorides with electron-withdrawing groups including the non-substituted led to higher yield than those with electron- donating groups. The acylation of alcohol with aliphatic acyl chlorides also proceeded smoothly affording high yields of the ester. It is noteworthy that carbon-carbon double bonds remained intact under the present reaction conditions while the reaction performed under basic reaction conditions led to a double bond isomerized product.6