1-(N-chloroacetylamino)-alkylphosphonic acids - synthetic precursors of phosphonopeptides.

General procedures of N-chloroacetylation of the representative 1-aminoalkylphosphonic acids (Gly(P), Ala(P), Val(P), Pgly(P) and Phe(P)) are described. These 1-(N-chloroacetylamino)-alkylphosphonic acids were converted into the corresponding glycylphosphonodipeptides (Gly-AA(P)) and/or related N-alkylglycylphosphonodipeptides (Me(n)Gly-AA(P)) in the course of ammonolysis/aminolysis. Physico-chemical properties of synthesized 1-(N-chloroacetylamino)-alkylphosphonic acids and phosphonodipeptides are characterized.

1-(N-trifluoroacetylamino)alkylphosphonic acids: synthesis and properties.

The 1-(N-trifluoroacetylamino)alkylphosphonic acids (TFA-AA(P)) - sub-products in the synthesis of O,O-dialkyl 1-(N-trifluoroacetylamino)alkylphosphonates and O,O-diethyl 1-aminoalkylphosphonates, were synthesized in two-stage transformations of 1-aminoalkylphosphonic acids including: trifluoroacetylation of 1-aminoalkylphosphonic acids (AA(P)) using a trifluoroacetic anhydride/trifluoroacetic acid reagent (AA(P) + TFAA/TFA-->2) and subsequent hydrolysis of the intermediary compounds 2 into desired TFA-AA(P) (2-->TFA-AA(P)). These intermediates 2 presented mixtures of the type of mixed anhydrides of TFAA and 1-(N-trifluoroacetylamino)alkylphosphonic, pyrophosphonic and polyphosphonic acids, which underwent rapid and quantitative conversion to corresponding TFA-AA(P) during treatment with an excess of water. The title acids were isolated by direct evaporation of the corresponding post-reaction mixtures, and their physicochemical proprieties, including deacylation abilities, were determined. TFA-AA(P) compounds can be re-converted into the starting amino acids AA(P) under respectively mild conditions (AA(P)-->TFA-AA(P)-->AA(P)).

Absolute configurations, predominant conformations, and tautomeric structures of enantiomeric tert-butylphenylphosphinothioic acid.

Vibrational absorption and circular dichroism spectra of dextrorotatory, levorotatory, and racemic mixture of tert-butylphenylphosphinothioic acid have been measured in CCl(4) solutions in the 2000-900 cm(-1) region. The conformations for both tautomeric structures of (S)-tert-butylphenylphosphinothioic acid are investigated using the B3LYP functional with the 6-31G* basis set. For the most stable conformation, the absorption and VCD spectra are predicted ab initio using the B3LYP functional with 6-31G*, 6-311G(2d, 2p), 6-31+G, and 6-311G(3df, 3pd) basis sets. A different functional, B3PW91, was also used with the 6-31G* basis set. The predicted spectra are compared to the experimental spectra. The comparison indicates that (-)-tert-butylphenylphosphinothioic acid is of the (S)-configuration and exists in only one tautomeric structure and one conformation in CCl(4) solution.

Absolute configuration, predominant conformations, and vibrational circular dichroism spectra of enantiomers of n-butyl tert-butyl sulfoxide.

Alkylation of the alpha-carbanion of (R)-(-)-tert-butyl methyl sulfoxide (4) with n-propyl bromide afforded (+)-n-butyl tert-butyl sulfoxide (1) to which the absolute configuration (R) was ascribed. This assignment was confirmed by X-ray analysis of the complex 6 obtained from the enantiomerically pure sulfoxide (-)-1 and mercury chloride. Vibrational absorption and circular dichroism spectra of (+)-1 were measured in CDCl3 solution in the 2000-900 cm(-1) region and compared with the ab initio predictions of absorption and VCD spectra obtained with density functional theory using the B3LYP/6-31G basis set for different conformers of (R)-1. This comparison indicated also that (+)-1 is of the (R)-configuration.

Absolute configurations, predominant conformations and tautomeric structures of enantiomeric tert-butylphenylphosphine oxides

Enantiomeric tert-butylphenylphosphine oxides have been isolated via resolution of the racemate with mandelic acid and investigated by using vibrational circular dichroism (VCD). Vibrational absorption and circular dichroism spectra of dextrorotatory, levorotatory, and racemic mixture of tert-butylphenylphosphine oxide have been measured in CDCl(3) and CHCl(3) solutions in the 2000-900 cm(-)(1) region. Experimental spectra are compared with the ab initio predictions of absorption and VCD spectra obtained with density functional theory using B3LYP/6-31G basis set for different tautomeric structures and conformers of (S)-tert-butylphenylphosphine oxide. This comparison indicates that (-)-tert-butylphenylphosphine oxide is of the (S)-configuration and indicates only one tautomeric structure and one conformation predominant for tert-butylphenylphosphine oxide in CDCl(3) and CHCl(3) solutions.

Vibrational circular dichroism and absolute configuration of chiral sulfoxides: tert-butyl methyl sulfoxide.

Mid-infrared vibrational unpolarised absorption and vibrational circular dichroism (VCD) spectra of CCl4 solutions of tert-butyl methyl sulfoxide (1) are reported. The spectra are compared to ab initio density functional theory (DFT) calculations carried out using two functionals, B3PW91 and B3LYP, and two basis sets, 6-31G* and TZ2P. The VCD spectra are calculated using Gauge-invariant atomic orbitals (GIAOs). The analysis of the VCD spectrum confirms the R(-)/S(+) absolute configuration of 1. The advantages and disadvantages of VCD spectroscopy in determining the absolute configurations of chiral sulfoxides are discussed.

Highly sensitive spectrophotometric microdetermination of sulphoxides.

The reaction of sulphoxides with trifluoroacetic anhydride and iodide in acetone medium to produce iodine, which can be used for their titrimetric determination, has been adapted for spectrophotometric determination of sub-mu mole amounts of sulphoxides.

A new method for the iodometric determination of sulphoxides.

A method is described for determination of sulphoxides through their reaction with iodide in a trifluoroacetic acid/acetone medium to produce iodine, which is then titrated with thiosulphate.