Stereoselective synthesis of muco-quercitol, (+)-gala-quercitol and 5-amino-5-deoxy-d-vibo-quercitol from d-mannitol

Synthesis of muco-quercitol, (+)-gala-quercitol, and 5-amino-5-deoxy-d-vibo-quercitol is described from d-mannitol using ring closing metathesis and diastereoselective dihydroxylations as key steps.     

Mild and efficient chemoselective deprotection of anomeric O-methyl glycosides with trityl tetrafluoroborate

A facile chemoselective deprotection of anomeric O-methyl glycosides has been achieved in good to excellent yields within 10-40 min with use of trityl tetrafluoroborate in dichloromethane at ambient temperatures. The present method is easily implemented and tolerates different functional groups.     

Novel bridged and caged C4-podophyllotoxin derivatives as microtubule disruptors: synthesis,cytotoxic evaluation and structure–activity relationship

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γ-Al2O3/triflic acid as cooperative catalysts for the tandem Michael addition/carbocyclization: An easy access to 2-substituted pyrrolo[2,1-a]isoquinolines and 3-substituted pyrrolidine-2,5-diones

A tandem Michael addition/carbocyclization of 3,4-dimethoxyphenethyl maleimide with carbon and sulfur nucleophiles is accomplished via a relay catalysis using γ-Al₂O₃/TfOH binary system. The X-ray Photoelectron Spectroscopy (XPS) analysis of binary system indicates the presence of AlF₃, AlO(OH) species_. This approach provides an easy access to 2-aryl or 2-thio aryl pyrrolo[2,1-a]isoquinolines in good yields in a tandem fashion. With suitable ratio of γ-Al₂O₃/TfOH binary system, the Michael addition of N/C/S nucleophiles to N-benzyl maleimide is also achieved. A key to the success of these reactions would be the generation of AlF₃, AlO(OH) species from γ-Al₂O₃ and TfOH, which might have delineated the disadvantageous background reactions usually displayed by a strong Brønsted acid such as TfOH.     

Chemoenzymatic synthesis of pyrrolo[2,1-b]quinazolinones: lipase-catalyzed resolution of vasicinone.

A facile synthesis of bronchodilatory pyrrolo[2,1-b]quinazoline alkaloids by azidoreductive cyclization strategy employing TMSCl-NaI and bakers' yeast is described. Both the chemical and enzymatic methods are mild and take place at room temperature in good yields. Further, synthesis and resolution of vasicinone has been carried out by employing different lipases. It has been observed that lipase PS provides acetate of (S)-vasicinone in 98% ee.     

Thioglycolates in the Synthesis of Bis(styryl)-sulfones

E, Z-Bis (styryl) sulfones (6), have been prepared by the Knoevenagel condensation of Z-styryl-sulfonylacetic acid (5) with araldehydes. The compound 5 was prepared by a novel route using thioglycolates and phenylacetylene. The configuration of 6 has been assigned based on IR and ¹H NMR spectral data.     

Thermal Decomposition of Thallium(I) Bis-oxalatodiaquaindate(III) Monohydrate

Thallium(I) bis-oxalatodiaquaindate(III) monohydrate was obtained by precipitation of indium(III) withoxalic acid from slightly acidic solution in the presence of thallium(I). The complex was subjected to chemical analysis. The thermal decomposition behavior of the complex was studied using TG, DTA and DTG techniques. The solid complex salt and the intermediate product of its thermal decomposition were characterized using IR absorption and X-ray diffraction spectra. Based on data from these physicochemical investigations the structural formula of the complex was proposed as Tl[In (C₂O₄)₂ (H₂O)₂]⋅H₂O. This revised version was published online in August 2006 with corrections to the Cover Date.