stable crystalline phosphorus ylides are obtained in excellent yields from the 1:1:1 addition reactionbetween hydantoins or thiohydantoins and dialkyl acetylenedicarboxylates in the presence oftriphenylphosphine. these phosphoranes undergo smooth intramolecular wittig reaction followedby an electrocyclic ring opening to produce dialkyl (e)-2-(2,5-dihydro-5,5-diaryl-2-thioxo-1h-imidazol-4-yl)fum...

tetrahydrobenzo[b]pyran derivatives 1 were utilized for the synthesis of several new pyrano[2,3-d]pyrimidine derivatives 2. compound 2 was obtained in the presence of ac2o/h2so4 (as a catalyst) and was confirmed by spectroscopic data such as ir, 1h nmr and 13c nmr. ab initio calculation was carried out to study geometric optimization, thermodynamic parameters, aromaticity and dynamic process of...

objective during the last three decades sesquiterpenoid lactones have emerged as one of the largest groups of plant products with over 3000 naturally occurring substances known. the genus artemisia characteristically contains this biologically active type of secondary metabolites. with respect to increasing interest in the cytotoxic, antibiotic, phototoxic and antineoplastic activities of sesqu...

The complete sequence-specific assignment of the 15N and 1H backbone resonances of the NMR spectrum of recombinant human interleukin 1 beta (153 residues, Mr = 17,400) has been obtained by using primarily 15N-1H heteronuclear three-dimensional (3D) NMR techniques in combination with 15N-1H heteronuclear and 1H homonuclear two-dimensional NMR. The fingerprint region of the spectrum was analyzed ...

The worldwide heparin contamination crisis in 2008 led health authorities to take fundamental steps to better control heparin manufacture, including implementing appropriate analytical and bio-analytical methods to ensure production and release of high quality heparin sodium product. Consequently, there is an increased interest in the identification and structural elucidation of unusually modif...

Content Synthetic scheme of phosphoramidite 9b ------------------------------------------------------------------S3 Figure S1 ------------------------------------------------------------------------------------------------------S4 Figure S2 ------------------------------------------------------------------------------------------------------S4 Figure S3 -----------------------------------------...

condensation of aromatic aldehydes with benzoyl acetone under specified conditions yieldedtwo series of polycarbonyl compounds in which the keto group is attached to olefinic linkage.spectral and analytical data revealed the formation of an unsaturated triketone from pyridine-3-carbaldehyde and unsaturated diketone from furfural, salicylaldehyde and 2-hydroxynaphthaldehyde. analytical, ir, 1h n...