An Asymmetric Synthetic Approach to the A-ring of the Taxol Family of Anti-Cancer Compounds*
A synthetic route developed for the preparation of the A-ring of Taxol family of molecules is reported. By means of an intramolecular Diels-Alder reaction an asymmetric approach to this ring has been accomplished. Also, initial studies to prepare the A ring using an intramolecular Diels-Alder reaction have been successful.
Synthesis, characterization, and antimicrobial activity of novel substituted 2H-chromenyl acrylates
The present study deals with conventional Witting olefination of 2H-chromene-3-carbaldehydes with stabilized ylide in the presence of dichloromethane to afford (2E)-ethyl-3-(4-chloro-2H-chromen-3-yl) acrylate derivatives. All the products were found to have E-geometry at C=C bond. The synthesized compounds were characterized by spectral data such as IR, 1H NMR and MS. Compounds were screened for antimicrobial activity against strains of gram positive, gram negative bacterial and fungal strains. All compounds showed good antibacterial and antifungal activity.
B11 N.m.r. Chemical Shifts. II. Amine-borate Ester Complexes, Alkoxydifluoroborane Trimers and Tetrahaloborate Ions1,2
ne The B/sup 11/ nmr spectra of BF/sub 2/Cl and BClF/sub 2/ were obtained, but no B/sup 11/-F/sup 19/ spin coupling could be observed. Some amine addition compounds of triethyl and triallyl borates were prepared and the B/sup 11/ chemical shifts are found to be dependent on reactant concentrations. Thus borate-amine exchange is taking place. Evidence that the compounds produced from the reaction of one mole of various borate esters and two moles of boron trifluoride are alkoxydifluoroborane cyclic trimers rather than the previously suggested coordinatlon complexes is presented. Chemical shifts for tetrahalo and tetrapseudohalo berate ions prepared in nitrobenzene are presented. (auth)