Letters in Organic Chemistry - Volume 2, Issue 8, 2005

This short report describes recent advances of metal trifluoromethanesulfonates as efficient catalysts in carbohydrate synthesis, including the topics of protection and glycosylation.

A concise highlight on recent advances in cascade/enyne RCM reactions of a range of substrates is discussed. Some of the reported strategies led to total synthesis of biologically active natural products.

We have prepared two polymeric materials from L-aspartic acid in supercritical carbon dioxide, polysuccinimide and copoly(succinimide-aspartate). The polysuccinimide was characterized by IR spectroscopy and GPC analysis. The copoly(succinimide-aspartate) product was also characterized by titrometric analysis. These natural materials may prove useful in reducing our dependence on petroleum products.

Synthesis of N-9-(fluorenylmethyloxycarbonyl)-a-aminopolyethylene glycol 900-ω-(2- cyanoethyl)-N-diisopropyl phosphoramidite is reported. Aminopolyethylene glycol 900- oligodeoxyribonucleotide conjugates were synthesized by solid phase approach by using the newly described phosphoramidite. The reactivity of the amino function in synthetic conjugates was demonstrated by reaction with activated esters of me Read More

The synthesis of some novel thiazolocoumarins is described. These polyheterocyclic compounds have been synthesized under microwave irradiation via the corresponding imino-1,2,3-dithiazoles besides cyanoimidoyl chloride derivatives.

The total synthesis of lyngbyabellin A, a biologically active metabolite from the marine cyanobacterium Lyngbya majuscula, is reported. There is flexibility in the approach which can readily allow structural modifications to be introduced.

An efficient synthesis of the marine cyanobacterium metabolite pitipeptolide A is presented. The approach incorporates a variety of peptide coupling methods, asymmetric synthesis and macrocyclization. The route is versatile and allows scope for structural modification.

Oxidative palladium couplings allow the preparation in high yields of different azepinoindole moieties. The use of CuCl2 as reoxidant leads to the formation of chloro derivatives instead of alkenes.

Solvothermal in situ ligand reaction of bis(2-pyridinylmethyl)amine (bpa) in the presence of Fe(ClO4)2 × 6H2O and NaN3 yielded the crystalline fluorescent organic heterocyclic compound 1, 1'-bis{3- (pyridin-2-yl)H-imidazo[1, 5-a]pyridine} 1 and the byproduct Fe(bpa)2(ClO4)2 2. Compound 1 is the first example of imidazo[1, 5-a]pyridine compound synthesized by in situ reaction under solvothermal conditions.

An efficient method for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs) using trichloroisocyanuric acid (TCICA) under solvent-free conditions is reported.

(R)-3-(2-Bromo-3-phenyl-acryloyl)-5,5-dimethyl-4-phenyl-oxazolidin-2-one 3 which is readily available from (R)-phenylglycine, was shown to be an effective chiral auxiliary for stereoselective Baylis- Hillman type reaction with aldehydes in the presence of SmI2.

Alkyl cyanides are prepared in good to excellent yields (average yield 93% )by treatment of alcohols and thiols with 2,4,6-trichloro[1,3,5]triazine/n-Bu4NCN in refluxing acetonitrile. This method is highly selective for conversion of 1° alcohols in the presence of 2° and 3° ones and thiols.

Cyanomethyl and 3-aminocrotonitrile anions, generated by cathodic reduction of CH3CN-Et4NClO4 solution under galvanostatic control are used in combination with gaseous CO2 as an alternative carboxylating reagent for the synthesis of oxazolidine-2,4-diones starting from halo amides. The synthesis has been carried out under mild conditions, avoiding any addition of classical bases, catalysts or toxic and dangerous chemical Read More

The catalytic activity of potassium salts of phthalimide (PPI) and succinimide (PSI), as organonucleophilic catalysts, has been investigated for the cyclotrimerization of isocyanates under solvent-free conditions. PPI showed better catalytic activity in comparison with PSI. Diverse and challenging isocyanates afforded the respective symmetrical isocyanurates in good to quantitative yields in an atom economic reaction without any Read More

A number of 6-methyl-4-N-(4'-aryloxybut-2'-ynyl)-N-methylaminopyran-2-ones (3a-g) on treatment with one equivalent of 3-chloroperoxybenzoic acid at 0-5 C during 25 minutes and then stirring at room temperature for 9 h afforded pyrrolo[3,2-c]pyrone derivatives (4a-g) in (80-85 %) yield. 6-Methyl-4-N-(4'- aryloxybut-2'-ynyl)N-methylaminopyran-2-ones (3a-g) were in turn prepared from 4-tosyloxy-6-methylpyran- 2-ones (1) Read More

A convenient, efficient, one-pot, novel process has been developed for the synthesis of carbamates from corresponding amines and alcoholic tosylates using basic resin/CO2 system is described.

An efficient amethodology for direct -thiocyanation of enolisable ketones using Cerium ammonium nitrate (CAN) and ammonium thiocyanates in presence of 18-Crown-6 at room temperature. The α- thiocyanoketones were obtained in excellent yields.

α-D-Arabinofuranosyl-(1→5)-[α-D-arabinofuranosyl-(1→3)]-α-D-arabinofuranosyl-(1→5)-Darabinofuranose (6) present in motif B of the Mycobacterium tuberculosis cell wall was regio- and stereospecifically synthesized by trichloroacetimidate method. The strategy greatly simplified the procedure for synthesizing 6.

The asymmetric ring-opening of monosubstituted epoxides with dithiophosphorus acids catalyzed by a (salen)Ti(IV) complex formed in situ from the reaction of Ti(OPr-i)4 and the chiral salen ligand derived from (1R,2R)-(+)-diaminocyclohexane and (R)-2,2'-diamino-1,1'- binaphthalene was realized. The resulting products were obtained with moderate enantioselectivity (up to 57% ee). High regioselectivity was observed for t Read More