Letters in Organic Chemistry - Volume 4, Issue 8, 2007

An artificial ribonucleoside with pyrimido[4,5-d]pyrimidine-2,4,5,7-(1H,3H,6H,8H)-tetraone (PPT) as a nucleobase was prepared, and its binding affinity for natural nucleosides, e.g., 2'-deoxyadenosine, 2'-deoxycytidine, 2'- deoxyguanosine, and thymidine derivatives, was investigated. This investigation revealed that, as expected, the nucleoside with PPT has good binding affinity for the four natural nucleosides to form with them some stable complexes in dimethyl sulfoxide, though the structure of the complex is not clear yet. Thus, this artificial nucleoside has high potential as a universal nucleoside.

The first palladium-catalyzed cross-coupling reaction between arenediazonium tetrafluoroborate salts and chloroformates to afford the corresponding substituted aryl carboxylic esters, in the presence of catalytic amounts of Pd(OAc)2 is described.

We here present a simple and efficient method for the preparation of 2'-substituted-thiazolomorphinanedienes 3-5. A protocol is also presented for yielding 3-demethoxy-14β-hydroxy derivatives of the thiazolomorphianedienes. The amino-, methyl- and phenyl-substituents connected in these compounds in a less rigid way to the “spacer” which offers the opportunity to test the effect of this sterically more flexible structure on the activity to opioid receptor subtypes.

Various types of aromatic and aliphatic sulfides are selectively oxidized to sulfoxides and sulfones with good to excellent yields using H2O2 35% p/V in the presence of catalytic amounts of Keggin heteropolyacid (H5PMo11Al0.5V0.5O40) using acetonitrile as solvent.

High exo-selectivity was achieved in the 1,3-dipolar cycloaddition of a cyclic azomethine ylide and phenyl vinyl sulfone or Opplozer's camphorsultam chiral dipolarophile leading to the synthesis of two novel tropane compounds.

A concise total synthesis of the furano-sesquiterpene (±)-euryfuran, a bioactive metabolite from some marine sponges, is presented. The key step is a highly diastereoselective titanium (III) catalyzed radical cyclization of a farnesol epoxyderivative.

Radicamine B 2, the enantiomer of natural radicamine B 5, was synthesized via a chiral nitrone derived from D-xylose in 10 steps with an overall yield of 15%.

A series of bifunctional compounds carrying cluster thiogalactosides L1-L6 as the cell targeting ligands were synthesized for gene delivery to hepatocytes. Tetra-antennary dendr-OMs4 5 was used as a scaffold for the attachment of three galactosides, while the other mesylate end was linked with cholesterol through poly(ethylene glycol) chain with different length. This design provided an effective entry for the synthesis of the bifunctional compound with hepatocytes targeting ability.

A series of chiral N-heterocyclic carbene precursors based on the dihydroimidazole framework were prepared from easily available chiral amines. The sequential attachment of these amines and mesitylamine to chloroacetyl chloride followed by reduction and subsequent ring closure gave the desired dihydroimidazolium salts in good yield.

3-mercapto-2-butanone undergoes a smooth reaction with electron-deficient symmetric and asymmetric acetylenes in the presence of catalytic amount of triphenylphosphine under neutral conditions to produce S-functionalized vinyl sulfides (Z/E isomers) in moderately high yields.

Some novel C2-symmetric bis-schiff base amino alcohols were prepared, the structure of which is similar to Salens`. Butyl lithium was chosen as the base to generate nucleophilic reagent in asymmetric addition to benzaldehyde using amino alcohols as chiral ligand. Only moderate enantioselectivity was observed, and by using the ligand with inverted configuration, the resulting alcohol has the inverted configuration.

KF-Al2O3 catalyzes the reaction of arylthioacetamides with α-bromo ketones to give fully substituted new indeno- and naphtho- fused thiophenes with good yields under solvent-free conditions by controlled microwave heating. A mechanism is proposed for the reaction course.

N-acylbenzotriazole mediated synthetic methodology for introducing methacryloyl (MA) group onto amino acids with complete retention of chirality has been disclosed.

We prepared the penta-N-acetyl-chitopentaose 2 by using recombinant Escherichia coli (E. coli) strains harboring the nodC gene (encoding chitooligosaccharide synthase) from Azorhizobium caulinodans. The deacetylase NodB removed the N-acetyl moiety from the nonreducing terminus of 2 to give tetra-N-acetyl-chitopentaose 3. N-Acylation of 3 with stearyl chloride was performed in DMF containing water and provided the corresponding lipo-chitopentaose nodulation factor 4.

2-Iodothiophene has been aminocarbonylated with simple unfunctionalised amines as well as with amino acid esters as N-nucleophiles in the presence of palladium(0) catalysts formed in situ from palladium(II) acetate and triphenylphosphine. While at low carbon monoxide pressure conversions of synthetic interest have been obtained with simple amines only, at higher carbon monoxide pressure various ketocarboxamides, formed via double carbon monoxide insertion, have been isolated with good yields (up to 85%).

Tris(2-hydroxyphenyl)methane derivatives (1) displayed excellent selectivity for chloride (Cl-), in comparison with bromide (Br-), iodide (I-) and nitrate (NO3 -) ions. This selectivity is attributed to the fit size and shape of chloride, which favor the formation of a stable host-guest complex through the multiple intermolecular hydrogen bonds between 1 and the chloride anion.

Forty-two 3-substituted 1-(5-formylfurfuryl)indolin-2-ones were synthesized and most of these compounds exhibited potent inhibitory activities against P. oryzae (MIC = 0.78-25 μg/mL) and human intestinal Caco-2 cells (IC50 = 0.19-9.42 μM). Eight compounds selected for further screening also showed inhibitory activities (IC50 = 1.84-10.32 μM) against human lung adenocarcinoma cells (SPC-A1).