No abstract

Stabilized phosphorus ylides, versatile intermediates in synthetic organic chemistry can be prepared by the novel reaction of dialkyl acetylenedicarboxylates (DAAD), triphenylphosphine (TPP) and acids such as phenols, imides, amides, enols, oximes and alcohols. The reaction involves an intermediate formed by the 1:1 conjugate addition reaction of the TPP to DAAD and concomitant protonation of the intermediate by an acid leads to vinyltriphenylphosphonium salts. The salts are unstable intermediates and converted to stabilized phosphorus ylides via Michael addition reaction. The stabilized phosphorus ylides are able to take part in the normal intramolecular Wittig reactions but they are not generally able to participate in the normal intermolecular Wittig reactions. The intermolecular Wittig reactions of the ylides are observed only with highly electron-poor carbonyl groups such as indane-1,2,3-trione. The ylides are converted to electron-poor alkenes via elimination of TPP in solvent-free conditions. Almost all of the final products are valuable families of compounds. †Dedicated to Professor Issa Yavari on the occasion of his 59th birthday.

Even though the therapeutic efficacy of numerous antimicrobial drugs has been well established, inefficient delivery can result in an inadequate therapeutic index. Gold nanoparticles have unique physicochemical properties such as large surface area to mass ratio and functionalizable structure. These properties can be applied to facilitate the administration of antimicrobial drugs, thereby overcoming some of the limitations in traditional antimicrobial therapeutics. In this study, gold nanospheres were used as a drug carrier system for gentamicin delivery to Staphylococcal infected foci. Conjugation of gentamicin with gold nanospheres was performed in HEPES buffer. The attachment of gentamicin to gold nanospheres was confirmed by UV/Vis spectroscopy. The HPLC and atomic absorption spectrometer analyses showed that 347 gentamicin molecules were attached to each gold nanosphere. Minimum inhibitory concentration and minimum bactericidal concentration studies showed the enhanced antibacterial effect of gentamicin-gold nanospheres complex in comparison with free gentamicin. The biodistribution study showed the localization of the complex at the site of Staphylococcal infection foci with high sensitivity in mouse model.

Triphenylphosphine (TPP), dialkyl acetylenedicarboxylates (DAAD), and acids such as phenols, imides, amides, enols, oximes and alcohols react with each other via a multicomponent reaction to produce stabilized phosphorus ylides. The reactions take place easily, through formation of intermediate formed by the Michael addition of the triphenylphosphine to dialkyl acetylenedicarboxylates and concomitant protonation of the intermediate by an acid leads to vinyltriphenylphosphonium salts. The salts are unstable intermediates and undergo a subsequent Michael addition leads to stabilized phosphorus ylides. In some cases ylide products are stable, but in other cases they cannot be isolated and appear to occur as intermediates on the pathway to an observed product. The stabilized phosphorus ylides are able to take part in the normal intramolecular Wittig reactions and produce a variety of heterocyclic or carbocyclic compounds, but they are not able to participate in the intermolecular Wittig reactions.

A one-pot synthesis of sterically congested phosphorus ylides in fairly high yields by the reaction of 2,2,6,6-tetramethyl-3,5-heptanedione, dialkyl acetylenedicarboxylates and triphenylphosphine is reported. The structures of these compounds were confirmed by IR, 1 H, 31 P and 13 C NMR spectroscopy, and X-ray single crystal structure determination. The NMR spectra (CDCl 3 as solvent) indicated that the compounds contained two rotamers for each ylide.