Letters in Organic Chemistry - Volume 3, Issue 7, 2006

Since their development, peptide nucleic acids (PNAs) have attracted much attention as potential pharmacological regulators of gene expression. Currently, applications of PNAs are restricted through deficiencies in target specificity, aqueous solubility and cellular uptake. This highlight reviews syntheses and hybridisation properties of recent PNA analogues designed to address these limitations..

3,4-Anhydro-2-deoxy-7-phenylglyconolactones were synthesized in six steps from diacetone-Dglucose. Construction of the cis-fused bicyclic systems of the corresponding 3,4-anhydro-2-deoxy-7- phenylglycolactones was achieved by a stereoselective substitution reaction at the anomeric position of the 1,2-O-isopropylidene group of the corresponding 1,2-O-isopropylidenefuranose derivatives. Another important reaction w Read More

Five, six and seven-membered intramolecular aromatic substitutions of imidazol-5-yl radicals are reported using both metal hydride/AIBN and photochemical conditions to give imidazo[5,1-a]isoindole, imidazo[5,1-a]isoquinoline and imidazo[5,1-a]benzazepine. Procedures for the synthesis of 5-bromo-(N-ω- phenylalkyl)imidazole radical precursors using 1,3-dibromo-5,5-dimethylhydantoin (dibromantin) and Nbromosuccinimi Read More

Kinetics of the base-catalyzed elimination of the phosphate group from short phosphoserinyl peptides and subsequent addition of β-mercaptoethanol to the dehydroalaninyl residue have been studied by following the reactions by RP HPLC in an 8:3:1 (v/v/v) mixture of water, DMSO and ethanol. The data obtained shows that neighboring side-chain-functionalized residues, including Asp, Tyr, Lys, His, Pro and As Read More

Four new spirostanes functionalized with the butyrolactone moiety were efficiently synthesized and submitted to preliminary biological tests. Two practical synthetic routes were designed to enable the incorporation of the γ-lactone functionality into rings A and B. Butyrolactones 5 and 10 showed a promising plant growth-promoting activity which renders them good candidates for further biological studies.

The Biginelli reaction efficiently catalyzed using commercially available iodine can afford the 3,4- dihydropyrimidin-2(1H)-ones in high yields under ultrasound irradiation.

A direct synthesis of substituted oxepin and spiroheterocycles has been achieved from substrates derived from 4-hydroxy-1,6-dimethyl pyridine-2-ones (1) by combining Claisen rearrangement and ring closing enyne metathesis. The RCEM proceeded smoothly under nitrogen atmosphere at room temperature in the presence of well-defined ruthenium catalyst A (10 mol%).

An easy and efficient procedure of preparation of symmetric organic carbonates in the ionic liquid tributylmethylammonium methanesulfonate ([tbma][MsO]) by dialkylation of potassium carbonate in mild conditions is proposed. Yields by weight of the isolated pure products are 95-97% in 24 h, working in excess of the eco-friendly potassium carbonate.

Michael type addition reaction of 5-substituted uracil derivatives to methyl acrylate and acrylonitrile has been studied. The regioselectivity of adducts has been observed due to the 5-substituent present in the uracil ring and the applied base. When triethylamine was used as a deprotonating agent, exclusively N-1 adducts were obtained. In the presence of DBU in DMF solution as the major products, N-3 adducts Read More

A short and general synthesis for the preparation of two series of conformationally constrained building block has been elaborated starting from amino acids. The intrinsic tendency of the dipeptide mimetic scaffold to induce β-turn formation was evaluated by computer methods. The results indicate that the diastereomers with the (R) configuration at the C-2 have high propensity to the type II β-turn formation.

The 3-benzyl-2H-chromenes (3 a-d), designed as potential inhibitors of picornavirus infections, were synthesized by a simple and convenient three-step procedure starting from the O-alkylation of the appropriate 2-(hydroxymethyl)phenols with 1-bromo-3-phenylpropan-2-ones. The resulting ethers (1 a-d) were converted to the corresponding triphenylphosphonium bromides (2 a-d) and finally cyclized by an intramolecular Wit Read More

The one-pot domino Michael-azacyclization process was applied to the synthesis of chiral Nsubstituted 1,4-dihydropyridines. Chiral enaminoesters were reacted with alkylidene malonate olefins or α,β- ethylenic aldehydes. The crucial role of the α-substituent of the starting enaminoester both on the diastereoselectivity and on the orientation of the reaction was clearly evidenced.

A simple and efficient acetylation protocol catalyzed by 10 mol% ceric ammonium nitrate has been devised. The reaction is fast and convenient producing acetates in excellent yields.

Synthesis of 4-methyl-5,5-dialkyl-2-oxo-2,5-dihydrofuran-3-carbonitriles is reported herein, using potassium carbonate as a base in an ionic liquid (BMIM, BF4) as solvent. The system ionic liquid and base can be recovered and reused.

We have developed a practical procedure for the synthesis of polyfunctional azolo[1,5- a]pyrimidines via the reactive species generated in situ from N-substituted lactams and Viehe's salt. The described protocol allowed for the introduction of three elements of diversity into the targeted molecules, including substituents originating from the i) nucleophile input, ii) lactam ring and iii) nucleophilic aromatic displacement (SN Read More

Butyryloxymethyloxirane (glycidyl butyrate) is efficiently reduced with potassium anions of alkalide K-, K+(15-crown-5)2. The reaction proceeds via the corresponding radical anion, which decomposes the homolytic alkyl-oxygen bond cleavage or dimerizes. The oxirane ring is not opened by K-. No organometallic is formed as an intermediate. This shows that the mechanism of the process under study differs from that proposed Read More

The preparation of 2-diphenylphosphinoyl-2'-halogenated biphenyls led to gaining interesting insight into the Suzuki-Miyaura coupling of ortho-halogenated penylboronic acids. Advantages and limitations on the use of halogenated biphenyls for the synthesis of diphosphine ligands are presented.