Trace Level Determination of Mesityl Oxide and Diacetone Alcohol in Atazanavir Sulfate Drug Substance by a Gas Chromatography Method.

A capillary gas chromatography method with a short run time, using a flame ionization detector, has been developed for the quantitative determination of trace level analysis of mesityl oxide and diacetone alcohol in the atazanavir sulfate drug substance. The chromatographic method was achieved on a fused silica capillary column coated with 5% diphenyl and 95% dimethyl polysiloxane stationary phase (Rtx-5, 30 m x 0.53 mm x 5.0 µm). The run time was 20 min employing programmed temperature with a split mode (1:5) and was validated for specificity, sensitivity, precision, linearity, and accuracy. The detection and quantitation limits obtained for mesityl oxide and diacetone alcohol were 5 µg/g and 10 µg/g, respectively, for both of the analytes. The method was found to be linear in the range between 10 µg/g and 150 µg/g with a correlation coefficient greater than 0.999, and the average recoveries obtained in atazanavir sulfate were between 102.0% and 103.7%, respectively, for mesityl oxide and diacetone alcohol. The developed method was found to be robust and rugged. The detailed experimental results are discussed in this research paper.

Structural insights of JAK2 inhibitors: pharmacophore modeling and ligand-based 3D-QSAR studies of pyrido-indole derivatives.

In this study we have performed pharmacophore modeling and built a 3D QSAR model for pyrido-indole derivatives as Janus Kinase 2 inhibitors. An efficient pharmacophore has been identified from a data set of 51 molecules and the identified pharmacophore hypothesis consisted of one hydrogen bond acceptor, two hydrogen bond donors and three aromatic rings, i.e. ADDRRR. A powerful 3D-QSAR model has also been constructed by employing Partial Least Square regression analysis with a regression coefficient of 0.97 (R(2)) and Q(2) of 0.95, and Pearson-R of 0.98.

Endodontic Treatment of Bilateral Maxillary First Premolars with Three Roots Using CBCT: A Case Report.

One of the determining factors for the success of endodontic therapy is understanding the morphological anatomy of the tooth structure and its variants in relation to its template anatomy. The internal anatomy of maxillary first premolars is particularly complex due to their variation in number of roots and canal configuration. However, the bilateral presence of three roots in a maxillary first premolar is of rare occurrence. This case report describes the unusual anatomy bilaterally detected in maxillary first premolars using Cone-Beam Computed Tomography.

Analysis of the discriminative inhibition of mammalian digestive lipases by 3-phenyl substituted 1,3,4-oxadiazol-2(3H)-ones.

We report here the reactivity and selectivity of three 5-Methoxy-N-3-Phenyl substituted-1,3,4-Oxadiazol-2(3H)-ones (MPOX, as well as meta and para-PhenoxyPhenyl derivatives, i.e.MmPPOX and MpPPOX) with respect to the inhibition of mammalian digestive lipases: dog gastric lipase (DGL), human (HPL) and porcine (PPL) pancreatic lipases, human (HPLRP2) and guinea pig (GPLRP2) pancreatic lipase-related proteins 2, human pancreatic carboxyl ester hydrolase (hCEH), and porcine pancreatic extracts (PPE). All three oxadiazolones displayed similar inhibitory activities on DGL, PLRP2s and hCEH than the FDA-approved anti-obesity drug Orlistat towards the same enzymes. These compounds appeared however to be discriminative of HPL (poorly inhibited) and PPL (fully inhibited). The inhibitory activities obtained experimentally in vitro were further rationalized using in silico molecular docking. In the case of DGL, we demonstrated that the phenoxy group plays a key role in specific molecular interactions within the lipase's active site. The absence of this group in the case of MPOX, as well as its connectivity to the neighbouring aromatic ring in the case of MmPPOX and MpPPOX, strongly impacts the inhibitory efficiency of these oxadiazolones and leads to a significant gain in selectivity towards the lipases tested. The powerful inhibition of PPL, DGL, PLRP2s, hCEH and to a lesser extend HPL, suggests that oxadiazolone derivatives could also provide useful leads for the development of novel and more discriminative inhibitors of digestive lipases. These inhibitors could be used for a better understanding of individual lipase function as well as for drug development aiming at the regulation of the whole gastrointestinal lipolysis process.

Identification, isolation and characterization of a new impurity in drug substance resulting from stress stability studies.

A new unknown impurity of cefoxitin formed during a gradient reverse phase high performance liquid chromatography (HPLC) analysis of stress stability samples of the drug substance cefoxitin, and the level of this impurity was found at up to 0.9%. This impurity was identified by LC-MS and characterized by (1H NMR, 13C NMR, LC/MS/MS, elemental analysis and FT-IR). Based on the spectral data, the impurity was named as, 3-[[(2R,3S)-[3-methoxy-3-N-[2-(thiophen-2-yl)acetamido]]-4-oxoazetidin-2-ylthio]-2-[(carbamoyloxy)methyl]]-acrylic acid. The structure of this impurity was also established unambiguously, prepared by isolation and co-injected into HPLC to confirm the retention time. To the best of our knowledge, this impurity has not been reported elsewhere. Structural elucidation of the impurity by spectral data is discussed in detail.

Validation of a sensitive ion chromatography method for determination of monoethylsulfate in Indinavir sulfate drug substance.

The present study relates to the optimization of an ion chromatography method to determine the content of monoethylsulfate at very low levels in Indinavir sulfate drug substance, and subsequent validation of the method to prove its suitability, reliability and sensitivity. Monoethylsulfate is a potential impurity of Indinavir sulfate, and may forms during the preparation as well as during storage. The ion chromatography method was developed in such a way that to enhance the detection level by introducing suppressor, and minimizing acquisition time by using suitable buffer of 3.2 mmole of sodium carbonate and 1 mmole of sodium hydrogen carbonate in water as eluent. The retention time of monoethylsulfate was about 9.5 min and the total acquisition time was 25 min. The optimized method was validated to prove its performance characteristics by demonstrating selectivity, sensitivity (limit of detection and quantification), linearity, precision and accuracy. The established limit of detection and quantification of monoethylsulfate in Indinavir sulfate by this method was found to be 24 ng/ml and 74 ng/ml respectively, and the overall percent accuracy (recovery) of samples evaluated at different concentration levels was found to be 97.1, indicating the sensitivity and accuracy of this optimized ion chromatography method.

The first structural study on a cyclic tricoordinate phosphorochloridite and a pentacoordinate phosphorane based on 1,2,3,5-protected myo-inositol--a new conformation of 1,3,2-dioxaphosphorinane ring.

Treatment of the phosphoramidite [myo-C(6)H(6)-2-[OC(O)Ph]-1,3,5-(O(3)CH)-4,6-(O(2)P-NH-i-Pr)] with o-chloranil affords the first example of inositol-based pentacoordinate phosphorane [myo-C(6)H(6)-2-[OC(O)Ph]-1,3,5-(O(3)CH)-4,6-(O(2)P-NH-i-Pr)(1,2-O(2)C(6)Cl(4))] (9) (X-ray structure) with a trigonal bipyramidal geometry at phosphorus. The six-membered 1,3,2-dioxaphosphorinane ring with the inositol residue has an unusual boat conformation in 9 which is quite different from that found in unrestrained rings investigated before, but is similar to that of its P(III) chloro precursor [myo-C(6)H(6)-2-[OC(O)Ph]-1,3,5-(O(3)CH)-4,6-(O(2)PCl)] (X-ray structure). Also, a convenient and chromatography-free procedure for the protected myo-inositol derivative [myo-C(6)H(6)-2-[OC(O)Ph]-1,3,5-(O(3)CH)-4,6-(OH)(2)] is reported.

Two phosphate-imidazole complexes with and without a hydrogen-bonded guest molecule.

The molecular structures of the complexes imidazolium 6,6'-di-tert-butyl-4,4'-dimethyl-2,2'-thiodiphenyl phosphate, C(3)H(5)N(2)(+).C(22)H(28)O(4)PS(-), (I), and imidazolium 6,6'-di-tert-butyl-4,4'-dimethyl-2,2'-thiodiphenyl phosphate diisopropyl hydrazodicarboxylate hemisolvate, C(3)H(5)N(2)(+).C(22)H(28)O(4)PS(-).0.5C(8)H(16)N(2)O(4), (II), have been determined. While (I) forms the expected hydrogen-bonded chain utilizing the two imidazole N-bound H atoms, in (II), the substituted hydrazine solvent molecule inserts itself between the chains. Compound (I) exhibits a strong N-H...O hydrogen bond, with an N...O distance of 2.603 (2) A. The hydrazine solvent molecule in (II) lies about a twofold axis and the N-bound H atoms are involved in bifurcated hydrogen bonds with phosphate O atoms. A C-bound H atom of the imidazolium cation is involved in a C-H...O interaction with a carbonyl O atom of the hydrazine solvent molecule.

Diverse modes of reactivity of dialkyl azodicarboxylates with P(III) compounds: synthesis, structure, and reactivity of products other than the Morrison-Brunn-Huisgen intermediate in a Mitsunobu-type reaction.

The reactivity of diethyl azodicarboxylate (DEAD)/diisopropyl azodicarboxylate (DIAD) with P(III) compounds bearing oxygen or nitrogen substituents is explored. Compounds with structures quite different from that of Morrison-Brunn-Huisgen intermediate R'(3)P(+)N(CO(2)R)N(-)(CO(2)R) (1), observed in the Mitsunobu reaction, have been established by using X-ray crystallography and NMR spectroscopy. Thus reactions with X(6-t-Bu-4-Me-C(6)H(2)O)(2)P-NH-t-Bu [X = S (8), CH(2) (9)] or XP(mu-N-t-Bu)(2)P-NH-t-Bu [X = Cl (14) or NH-t-Bu (15)] and DEAD/DIAD lead to phosphinimine-carbamate-type of products X[6-t-Bu-4-Me-C(6)H(2)O](2)P[N-t-Bu][N(CO(2)R)NH(CO(2)R)] [X = S, R = Et (16); X = CH(2), R = Et (17); X = CH(2), R = i-Pr (18)] or XP(mu-N-t-Bu)(2)P(N-t-Bu)[N-(CO(2)-i-Pr)-N(H)(CO(2)-i-Pr) [X = Cl (19), NH-t-Bu (20)]. Treatment of 19 with 2,2,2-trifluoroethanol afforded the product [(CF(3)CH(2)O)P(mu-N-t-Bu)(2)P(+)(NH-t-Bu)[N(CO(2)-i-Pr)(HNCO(2)-i-Pr)]][Cl(-)] (21) whose structure is close to one of the intermediates proposed in the Mitsunobu reaction. The isocyanate CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P-NCO (10) underwent 1,3-(P,C) cycloaddition with DEAD/DIAD to lead to CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P[N(CO(2)R)N(CO(2)R)-C(O)-N] [R = Et (22), i-Pr (23)]. Reaction of 22-23 with 1,1'-bi-2-naphthol or catechol leads to novel tetracoordinate CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P(2,2'-OC(10)H(6)-C(10)H(6)-OH)[NC(O)-(CO(2)R)NH(CO(2)R)] [R = Et (24), i-Pr (25)] or pentacoordinate CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P(1,2-O(2)C(6)H(4))[NHC(O)-N(CO(2)R)NH(CO(2)R)] [R = Et (26), i-Pr (27)] compounds in which the original NCO residue is retained; this mode of reactivity is quite different from that observed for the MBH betaine 1. In 27, the nitrogen, rather than the oxygen, occupies an apical position of the trigonal bipyramidal phosphorus violating the commonly assumed preference rules for apicophilicity. It is shown that the previously reported azide derivative 3, obtained from the reaction of 11 with DIAD, undergoes a Curtius-type rearrangement to lead to the fused cyclodiphosphazane [(CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2))P(OC(O-i-Pr)NN(CO(2)-i-Pr)N)](2) (28); this compound is in equilibrium with its monomeric form in solution at >300 K. Finally, reaction of S(6-t-Bu-4-Me-C(6)H(2)O)(2)P(OPh) (13) with DIAD gave the hexacoordinate compound S[6-t-Bu-4-Me-C(6)H(2)O](2)P(OPh)[N(CO(2)-i-Pr)NC(O-i-Pr)O] (30) with an intramolecular S-->P bond. X-ray crystallographic evidence for compounds 16, 19, 21, 22, 25, 27, 28, and 30 has been provided.