Letters in Organic Chemistry - Volume 7, Issue 3, 2010

Model compounds of oxidized anhydroglucose units in cellulosic materials, carrying 13C isotopic labels at specific positions, have been synthesized starting from commercially available 1-13C-D-glucose (14.7%) and 3-13C-Dglucose (6.3%), respectively, over 10 linear steps. To ensure high yields, the synthetic route was optimized with non-labeled material beforehand. The labeled compounds are used in studies of chromophore formation, yellowing, brightness reversion and aging of cellulosics.

Hydroxymethylnitrofurazone presents in vitro activity against Trypanosoma cruzi. The optimization of the synthesis of this compound was performed through a 32 factorial statistical design. Quadratic model produced the best response surface predicting a maximum yield (82%) close to the center design point with a seven hours reaction and a 1:1.5 (NF:K2CO3) ratio.

Several α-D/L-arabino and β-D/L- xylonucleosides were synthesized in good yields under mild conditions by N-glycosylation of 1-O-acetyl D/L- arabino, and xylofuranose, with silylated nucleobases (uracil, thymine and 6- azauracil) in acetonitrile using natural phosphate (NP) coated with potassium iodide in BSA as catalyst.

The first example of the synthesis of cap analog derivatives having 2, 6-diaminopurine nucleoside has been described. The desired modified cap analogs m7G[5']ppp[5']2-aminoA 6 and m2 7,3'OG[5']ppp[5'] 2-aminoA 7 were obtained from the coupling reaction of imidazolide salt of 2-amino adenosine [5'] monophosphate with its corresponding TEA salt of m7GDP in the presence of ZnCl2 as a catalyst in 73% and 64% yield, respectively. The structures of new cap analogs were confirmed by LC/MS, 1H and 31P NMR.

Design, synthesis and characterization of new series of first-generation V-shaped dendrimers bearing phenylenevinylene dendritic branches in periphery and pyridine as a core is described. A preliminary study of the optical properties of the resulting compounds was conducted by UV/vis and fluorescence spectroscopy.

A simple and efficient method for the synthesis of quinoxalines derivatives has been developed. All the reactions were carried out in presence of niobium (V) chloride at acetonitrile reflux conditions. The method is applicable to a variety of diketones and 1, 2-phenylenediamines to afford the corresponding derivatives in excellent yields.

Oxazolidin-2-one was found to be a facile ligand for the N-arylation of pyrrole, indole, and imidazole with aryl and heteroaryl iodides, bromides, and chlorides by applying CuI as catalyst. The easy preparation, commercial availability, lower molecular weight, and broad substrate applicability, as well as substituent compatibility of this catalysis system render oxazolidin-2-one great advantages over the Cu-catalyzed methods that have already been utilized in a number of applications.

Chiral phosphoric acid as organocatalyst for the diastereo- and enantioselectivity 1,4-conjugate addition of a variety of β-ketoesters to nitroolefins was firstly developed, providing the corresponding adducts in high yield (up to 97%) with moderate diastereoselectivities (up to 2.6:1 dr) and enantioselectivities (up to 58% ee).

A facile and efficient addition of isocyanates with epoxides in the presence of MgI2 etherate was reported in good yields. The corresponding 2-oxazolidinone could be easily converted into 1,2,3-triazole-oxazolidinone by click reaction in excellent yield.

The chlorination of the new type Baylis-Hillman adducts by bis(trichloromethyl)carbonate (BTC) with the aid of catalytic amount of triphenylphosphine oxide (Ph3PO) was achieved with high yields and high stereoselectivities. A plausible mechanism is presented.

The reaction of P-chloro-benzo-1,3,2-dioxaphospholane with diethylamine, (S)-(-)-α-phenylethylamine and (1R,2S,5R)-(-)-menthol afforded the corresponding amino- and cycloalkoxy derivatives. The P-(diethylamino)- benzodioxaphospholane was converted to the corresponding platinum complex of cis-PtL2Cl2 type. It was observed that under not strictly anhydrous conditions, one of the benzodioxaphospholane rings suffered ring opening. The stereostructures and the relative energies of the dioxaphospholane-related platinum complexes were calculated by the B3LYP/6-31G* - LANL2DZ, as well as the PM6-DH methods. The phenylethylamino- and menthylbenzodioxaphospholanes were stabilized as the corresponding P-boranes. Decomplexation of a few P-boranes was studied and the optimum conditions were evaluated.

Our recent study on Artocarpus odoratissimus (Moraceae) has resulted in the purification of a new prenylated pyranoflavone derivative artosimmin (1) and traxateryl acetate (2). Details of structural elucidations associated with 1 and 2 are reported by combining 1D, 2D NMR and mass spectrometric methods. Compound 2 is obtained for the first time from this species. Furthermore, the biological assay results exhibited compound 1 to be significantly cytotoxic against cancer cell lines (HL-60 & MCF-7) and also possessed antioxidant properties toward 1,1-diphenyl-2-picrylhydrazyl radical (DPPH).

Enantioselective hydrolysis of methyl ester of (±)-C75 was successfully accomplished by means of Acylase I from Aspergillus to afford (2R,3S)-(+)-C75 with 96% e.e. The unreacted methyl ester was recovered with >99% e.e. This latter compound was either chemically or enzymatically hydrolyzed to furnish (2S,3R)-(-)-C75 with >99% e.e.

Mild combination of nitro urea, derived from urea nitrate, and silica sulfuric acid (SiO2OSO3H) might act as an efficient oxidizing media, which could be able to oxidize different types of heterocyclic compounds including urazoles and 1,4-dihydropyridines. The process presented here is operationally simple, environmentally benign, and reactions have been mildly carried out in dichloromethane at room temperature.

Montmorillonite K-10 has been used in many organic preparations as a good solid catalyst. In this review, we wish to report some applications of this catalyst in organic reactions.

The preparation and use of Animal Bone Meal (ABM) as natural catalyst is described for C-S bond formation by thia-Michael addition. This new natural heterogeneous method led to β-sulfinyl adducts in very high yields after only a few minutes. Influence of the thiol derivatives and substitution on chalcones is discussed.