Solventless synthesis of acyl phosphonamidates, precursors to masked bisphosphonates

A series of acyl phosphonamidates, the synthetic precursors to bisphosphonates, have been readily prepared from phosphoramidite type reagents and a range of acid chlorides.

Enantiodifferentiation of alpha-hydroxyalkanephosphonic acids in 31P NMR with application of alpha-cyclodextrin as chiral discriminating agent

Alpha-cyclodextrin was shown to be convenient chemical shift reagent for determination of the enantiomeric composition of alpha-hydroxyphosphonic acids by means of 31P NMR. The developed methodology appeared to be reliable, repetitive, easy to perform and simple for interpretation. Enantiomeric discrimination in the 31P NMR spectra for 12 of 13 studied hydroxyphosphonates was achieved, with baseline separation of resonances obtained for eight compounds. In those cases, the chemical nonequivalence values ranged from 0.069 to 0.313 ppm. The studies showed that enantioselectivity is strongly influenced by the solution pD and the optimal condition was found at pD 2 or 10 depending on the guest structure. On the basis of the ROESY spectra the complexation modes of selected hydroxyphosphonates with alpha-cyclodextrin was postulated.

Diisopropyl [(benzoyl-amino)-(phen-yl)meth-yl]phospho-nate

The title compound, C(20)H(26)NO(4)P, has been obtained by the reaction of benzoyl chloride and diisoprop-yl[amino-(phen-yl)meth-yl]phospho-nate. The dihedral angle between the planes of the benzoyl-amino group and the phenyl ring is 77.0 (2)°. The crystal structure is stabilized by strong inter-molecular N-H⋯O hydrogen bonds between the doubly bonded phosphoryl O atom and the amide N atom which link the mol-ecules into pairs about a center of symmetry.

Synthesis of phosphorothioates using thiophosphate salts

Reactions of O,O'-dialkyl thiophosphoric acids with alkyl halides, in the presence of a base, provide a direct synthetic route to phosphorothioates via O,O'-dialkyl thiophosphate anion formation. Studies on the reaction of ambident nucleophile ammonium O,O'-diethyl thiophosphate with benzyl halides and tosylate in different solvents show that only S-alkylation is obtained. Reaction of this ambident nucleophile with benzoyl chloride (a hard electrophile), gave the O-acylation product. A simple, efficient, and general method has been developed for the synthesis of phosphorothioates through a one-pot reaction of alkyl halides with the mixture of diethyl phosphite in the presence of triethylamine/sulfur/and acidic alumina under solvent-free conditions using microwave irradiation.