A Cyclopropanol-Based Strategy for Subunit Coupling: Total Synthesis of (+)-Spirolaxine Methyl Ether

A strategy for ketone synthesis with cyclopropanols as intermediates and its application to (+)-spirolaxine methyl ether is described. The synthesis also features an application of Fu's alkyl-alkyl Suzuki coupling.

Response Accuracy and Odor Sampling Time in Mice Trained to Discriminate between Enantiomers of Carvone and Those of Terpinen-4-ol

Response accuracy and odor-sampling times were used to compare the ability of mice to detect (+)-carvone and (+)-terpinen-4-ol and to discriminate between enantiomers of carvone and of terpinen-4-ol. Except for increased odor sampling when mice were first exposed to the (+)-carvone odor, there was no difference in odor-sampling time or response accuracy in tests of odor detection or in discriminating between enantiomers of these odorants. These results fail to support the suggestion that odorants that produce different patterns of olfactory bulb activation should be easier to discriminate than those that produce much more similar patterns of bulbar activation.

Syntheses of the 3- and 4-thio analogues of 4-nitrophenyl 2-acetamido-2-deoxy-beta-D-gluco- and galactopyranoside

The syntheses of 4-nitrophenyl beta-glycosides of the 3-thio and 4-thio analogues of the two principal 2-acetamido-2-deoxy-hexoses found in living systems, GlcNAc and GalNAc, are described. While synthesis of the 4-thio analogues could be achieved via nucleophilic displacements of sulfonate derivatives with thioacetate, problems with neighbouring group acetamido participation necessitated the use of sulfamidate intermediates for the 3-thio analogues. These 3- and 4-thio analogues are employed in the chemo-enzymatic synthesis of thio-oligosaccharide analogues of structures present in glycosaminoglycans, glycoproteins and glycolipids.

Swelling, erosion and release behavior of alginate-based matrix tablets

Hydrophilic matrix tablets based on the alginate system have been used in relation to their possible function in modified drug delivery formulations using metronidazole as a model drug. The matrix tablets were prepared by direct compression using different grades of alginate. The effect of some factors (i.e. particle size of drug, additive used, and pH of medium) on drug release from alginate-based matrix tablets was also investigated. Swelling, erosion, and in vitro release studies of the matrix tablets were carried out in 0.1N HCl or phosphate buffer (pH 6.8). The alginate-based matrix tablets swelled or eroded while in contact with the aqueous medium and formed a continuous gel layer or underwent combination of swelling and erosion. The swelling action of alginate matrices is controlled by the rate of its hydration in the medium. Different grades of alginate insignificantly influenced the matrix swelling in acidic medium but significantly influenced in neutral medium. The presence of ammonium or calcium salts induced tablet disintegration in acidic medium. However, incorporation of calcium acetate and sodium bicarbonate can alter the tablet swelling in acidic medium. Release studies showed that all investigated factors influence the drug release. The extent of matrix swelling, erosion, and diffusion of drug determined the kinetics as well as mechanism of drug release from alginate-based matrix tablets. Most of the release data in acidic medium showed a good fit into Korsmeyer-Peppas equation but fitted well with zero-order release model, in neutral medium.

Substituent and solvent effects on electronic spectra of some substituted phenoxyacetic acids

The effects of substituents and solvents have been studied through the absorption spectra of nearly 19 para- and ortho-substituted phenoxyacetic acids in the range of 200-400 nm. The effects of substituent on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed.

Superheated water extraction and phase transfer methylation of phenoxy acid herbicides from solid matrices

Phase transfer catalytic methylation was applied to directly derivatise chlorophenoxy acid herbicides in superheated water extracts from sand and soil samples. The extractions were carried out at 120 degrees C statically for 5 min and then dynamically for 10 min at 1.0 mL min(-1) using water at pH 11.0 for a sand matrix and a flow rate of 0.5 mL min(-1) at pH 7.0 for soil samples. The methylation was carried out on-line on the extraction solution with ultrasonication at 80 degrees C, using either 0.05 mmol tetrabutylammonium bromide (TBAB) or 0.0125 mmol cetyltrimethylammonium bromide (CTAB) as phase transfer catalysts with 0.20 mmol methyl iodide in 2.0 mL dichloromethane trapping solvent. The former catalyst provided a higher yield but the latter gave fewer interfering peaks. The recoveries of most chlorophenoxy acids using the TBAB catalyst ranged from 67 to 105% for sand and from 82 to 114% for soil sample, except phenoxyacetic acid, 2-(2, 4-dichlorophenoxy)propanoic acid and 1-naphthaleneacetic acid, while those by using CTAB were slightly lower. Detection limits of all the analytes extracted from sand using TBAB catalyst were in a range of 5.3-16 microg g(-1) analysed by using gas chromatography with flame ionization detection (GC-FID).

Validation of an efficient method for the determination of pesticide residues in fruits and vegetables using ethyl acetate for extraction

In this study, a version of the "quick, easy, cheap, effective, rugged, and safe" (QuEChERS) method was modified to use ethyl acetate (EtOAc) rather than acetonitrile (MeCN) for extraction in the determination of multiple pesticide residues in fruits and vegetables. EtOAc is better suited than MeCN for gas chromatographic (GC) analysis with electron capture detection (ECD) and nitrogen-phosphorus detection (NPD). The method entailed extraction of 30 g chopped sample plus 5 g NaHCO(3) and 30 g anhydrous Na(2)SO(4) with 60 mL EtOAc using a probe blender. After a centrifugation step, removal of residual water and cleanup were performed using dispersive solid-phase extraction (dispersive-SPE) with MgSO(4) and primary secondary amine (PSA) sorbent. (14)C-labeled chlorpyrifos with liquid scintillation counting was used to assist in optimizing and characterizing the method, and GC-ECD and GC-NPD were used for analysis of 24 selected pesticides. The method was validated using tomato, apple and frozen green bean matrices spiked at 0.05, 0.5, and 5 mg/kg. For 22 of the analytes, recoveries averaged 93% for all three commodities over the validation range with a relative standard deviation of 10% (n = 1182). Lower recoveries of dichlorvos were obtained with the method and iprodione determination was compromised in the green beans by an interfering peak. Typical limits of detection were 0.005-0.01 mg/kg with the method.

The efficacy of techniques for the disinfection of artificial sub-surface dentinal caries lesions and their effect on demineralization and remineralization in vitro

OBJECTIVES

The efficacy of three techniques for the disinfection of artificial sub-surface root caries lesions and their response to subsequent episodes of de- and remineralization was investigated quantitatively in vitro.

METHODS

Sub-surface dentinal lesions (n=20), cut into four experimental blocks and deliberately contaminated with Streptococcus mutans, were subject to either steam autoclaving (121 degrees C, 5min), gamma irradiation (4100Gy), immersion in 0.1% (w/v) thymol-distilled water solution (24h) or reserved as a control. Next, the lesions were incubated aerobically in sterile nutrient broth for 24h at 37 degrees C and resultant cultures plated onto blood agar and neutralisation agar. Ten blocks from each experimental group were then immersed in an acidic buffer solution or exposed to artificial saliva for 5 days. Baseline changes in the mineral content and distribution of the lesions were assessed by transverse microradiography (TMR).

RESULTS

Micro-organisms were recovered from each control block and one block treated by gamma irradiation. Steam autoclaving and immersion in a thymol solution significantly decreased (p<0.05) the amount of mineral lost from the body of lesions subject to a further acid challenge. Mineral ion uptake by lesions exposed to artificial saliva was significantly increased (p<0.05) through disinfection by steam autoclaving.

CONCLUSIONS

Gamma irradiation proved the most acceptable method for the disinfection of sub-surface root dentine lesions having the least adverse effect on demineralization and remineralization.

Synthesis and antitubercular activity of substituted novel pyrazoline derivatives

A series of 2-2-methoxy-4-[5-(substituted phenyl)1-(4-pyridylcarbonyl)-4,5-dihydro-1H-3-pyrazolyl] phenoxyacetic acid were synthesized by the reaction between isoniazid (INH) and chalcones, and were tested for their antimycobacterial activity in vitro against Mycobacterium tuberculosis H37Rv and INH resistant M. tuberculosis using BACTEC-460 radiometric system and agar dilution method. Among the synthesized compounds, Compounds II 2-4-[5-(4-hydroxyphenyl)-1-(4-pyridylcarbonyl)-4,5-ihydro-1H-3-pyrazolyl]-2-methoxy phenoxy acetic acid was found to be most active agent against M. tuberculosis H37Rv (MTB) and INH resistant M. tuberculosis (INHR-MTB), with minimum inhibitory concentration of 0.12 microM, when compared to INH 5.6-fold more active against MTB and 78-fold more active against INHR-MTB, respectively.

Calculation for liquid–liquid equilibria of quaternary alkane–ethyl acetate–methanol–water systems used in counter-current chromatography

The calculation of liquid-liquid equilibrium compositions of solvent systems is very important for the work on counter-current chromatography (CCC), especially the phase composition and volume ratio obtained from liquid-liquid equilibrium calculation. In this work, liquid-liquid equilibria of quaternary Arizona solvent systems, alkane-ethyl acetate-methanol-water, and related ternary systems are correlated and predicted using the non-random two-liquid model (NRTL). Hexane, heptane and isooctane are the used alkanes. The parameters in the model are regressed only with the special systems considered. Detailed comparison with experimental data shows that liquid-liquid equilibria of these systems can be predicted with greatly improved accuracy as compared to the group contribution method (UNIFAC).

Hepatoprotective effect of the ethyl acetate extract of Teucrium polium L. against carbontetrachloride-induced hepatic injury in rats

Hepatoprotective activity of the ethyl acetate extract of Teucrium polium L. was investigated using rats with CCl4-induced liver damage. Specific biochemical parameters (glutathione peroxidase, superoxide dismutase, reduced glutathione and total antioxidative status) were estimated in blood and in liver homogenate. Lipid peroxidation in CCl4-intoxicated rats was evidenced by a marked increment in the levels of thiobarbituric acid reactive substances. Histopatological examinations of the liver were undertaken to monitor the liver status. Silymarin was used as a standard to compare the hepatoprotective activity of the extract. Some biochemical parameters in groups treated with the Teucrium polium extract at a dose of 25 mg kg(-1), showed significantly different values than that of the CCl4--treated group. The liver biopsy of all experimental rat groups treated with the Teucrium polium ethyl acetate extract showed significant restoration of the normal histomorphological pattern of liver cells. The study substantiates the potential hepatoprotective activity of the ethyl acetate extract of Teucrium polium L.

Equilibrium and formation/dissociation kinetics of some Ln(III)PCTA complexes

The protonation constants () of 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA) and stability constants of complexes formed between this pyridine-containing macrocycle and several different metal ions have been determined in 1.0 M KCl at 25 degrees C and compared to previous literature values. The first protonation constant was found to be 0.5-0.6 log units higher than the value reported previously, and a total of five protonation steps were detected (log = 11.36, 7.35, 3.83, 2.12, and 1.29). The stability constants of complexes formed between PCTA and Mg2+, Ca2+, Cu2+, and Zn2+ were also somewhat higher than those previously reported, but this difference could be largely attributed to the higher first protonation constant of the ligand. Stability constants of complexes formed between PCTA and the Ln3+ series of ions and Y3+ were determined by using an "out-of-cell" potentiometric method. These values ranged from log K = 18.15 for Ce(PCTA) to log K = 20.63 for Yb(PCTA), increasing along the Ln series in proportion to decreasing Ln3+ cation size. The rates of complex formation for Ce(PCTA), Eu(PCTA), Y(PCTA), and Yb(PCTA) were followed by conventional UV-vis spectroscopy in the pH range 3.5-4.4. First-order rate constants (saturation kinetics) obtained for different ligand-to-metal ion ratios were consistent with the rapid formation of a diprotonated intermediate, Ln(H(2)PCTA)(2+). The stabilities of the intermediates as determined from the kinetic data were 2.81, 3.12, 2.97, and 2.69 log K units for Ce(H(2)PCTA), Eu(H(2)PCTA), Y(H(2)PCTA), and Yb(H(2)PCTA), respectively. Rearrangement of these intermediates to the fully chelated complexes was the rate-determining step, and the rate constant (k(r)) for this process was found to be inversely proportional to the proton concentration. The formation rates (k(OH)) increased with a decrease in the lanthanide ion size [9.68 x 10(7), 1.74 x 10(8), 1.13 x 10(8), and 1.11 x 10(9) M(-1) s(-1) for Ce(PCTA), Eu(PCTA), Y(PCTA), and Yb(PCTA), respectively]. These data indicate that the Ln(PCTA) complexes exhibit the fastest formation rates among all lanthanide macrocyclic ligand complexes studied to date. The acid-catalyzed dissociation rates (k1) varied with the cation from 9.61 x 10(-4), 5.08 x 10(-4), 1.07 x 10(-3), and 2.80 x 10(-4) M(-1) s(-1) for Ce(PCTA), Eu(PCTA), Y(PCTA), and Yb(PCTA), respectively.

Experimental and Computational Thermochemical Study of 2- and 3-Thiopheneacetic Acid Methyl Esters

Thiophene-based compounds have widespread use in modern drug design, biodiagnostics, electronic and optoelectronic devices, and conductive polymers. The present study reports an experimental and computational thermochemical study on the relative stabilities of 2- and 3-thiopheneacetic acid methyl esters. The enthalpies of combustion and vaporization were measured by a rotating-bomb combustion calorimeter, Calvet microcalorimetry, and correlation gas chromatography, and the gas-phase enthalpies of formation at T=298.15 K were determined. Standard ab initio molecular orbital calculations at the G3 level were performed, and a theoretical study of the molecular and electronic structure of the compounds studied was carried out. Calculated enthalpies of formation, using atomization and isodesmic reactions are in very good agreement with the experimental results.

The reactivity of epoxides with lithium 2,2,6,6-tetramethylpiperidide in combination with organolithiums or grignard reagents

The scope and limitations of lithium 2,2,6,6-tetramethylpiperidide (LTMP)-modified reductive alkylation of epoxides is detailed. A variety of organolithiums are added to terminal and 2,2-disubstituted epoxides in the presence of LTMP to generate alkenes in a completely regio- and highly stereoselective manner. Arylated alkenes, dienes, allylsilanes, and enynes are accessed using this procedure. The methodology is applied in the synthesis of the roller leaf moth pheromone, (3E,5Z)-dodecadienyl acetate. The corresponding reaction without LTMP has also been examined, and a study using deuterated epoxides provides insight into the mechanism. In the presence of LTMP, Grignard reagents are also shown to produce E-alkenes directly from epoxides.

Colorimetric Detection of Cu[II] Cation and Acetate, Benzoate, and Cyanide Anions by Cooperative Receptor Binding in New α,α‘-Bis-substituted Donor−Acceptor Ferrocene Sensors

New ferrocene derivatives bearing two donor-acceptor systems are capable of selectively sensing cations and anions by cooperative binding of the two alpha,alpha'-groups bonded to the ferrocene nucleus, thus permitting the naked-eye selective colorimetric detection of copper[II] cation and acetate, benzoate, or cyanide anions, which are ions of toxicological and biological relevance.

BF2 complex of fluorinated dipyrrolyldiketone: a new class of efficient receptor for acetate anions

The beta-fluorinated derivative (2b) of the 1,3-dipyrrolyl-1,3-propanedione BF2 complex has been prepared from 3,4-difluoropyrrole and malonyl chloride, followed by treatment with BF3.OEt2. Despite the simple, acyclic, and neutral structure, 2b exhibits efficient 1:1 binding for anions in CH2Cl2 using the bridging CH and pyrrole NH as interaction sites. The binding constant (Ka) of 2b for acetate (CH3CO(2-)), associating more effectively than anions such as F-, Cl-, Br-, H2PO(4-), and HSO(4-), is estimated to be 9.6 x 10(5) M(-1), approximately 9 times larger than that of the beta-H derivative 2a (1.1 x 10(5) M(-1)). The UV-vis and fluorescence spectral changes of 2b elucidate the effective recognition of an amino acid, such as phenylalanine, in the anionic form; this is also supported by CD spectral changes with mirror images by L- and D-isomers. Furthermore, in the solid state, BF2 complex 2b provides Cl- -bridged supramolecular networks and, in sharp contrast, deprotonated "anionic" self-assembled structures by F- binding.

Characterization of PHB storage in activated sludge extended filamentous bacteria by automated colour image analysis

The storage of poly-beta-hydroxybutyrate (PHB) in extended filamentous bacteria from activated sludge was monitored by Sudan Black staining: PHB granules were blue in the reddish filaments counterstained by safranin. By quantitative image analysis of colour images grabbed on an optical microscope, the distribution of the PHB loading of the extended filaments was estimated by determination of the proportion of blue pixels of their skeleton. The method was applied for different feed compositions to demonstrate its ability to monitor the PHB synthesis and storage capacity of filamentous bacteria in mixed cultures. Fast PHB storage, within a few hours, could be observed with acetate-based feeding solutions but the storage rate decreased with more complex feeds (meat extract based feed, wastewater).

A Marcus treatment of rate constants for protonation of ring-substituted alpha-methoxystyrenes: intrinsic reaction barriers and the shape of the reaction coordinate

Rate and equilibrium constants were determined for protonation of ring-substituted -methoxystyrenes by hydronium ion and by carboxylic acids to form the corresponding ring-substituted alpha-methyl alpha-methoxybenzyl carbocations at 25 degrees C and I = 1.0 (KCl). The thermodynamic barrier to carbocation formation increases by 14.5 kcal/mol as the phenyl ring substituent(s) is changed from 4-MeO- to 3,5-di-NO2-, and as the carboxylic acid is changed from dichloroacetic to acetic acid. The Brønsted coefficient alpha for protonation by carboxylic acids increases from 0.67 to 0.77 over this range of phenyl ring substituents, and the Brønsted coefficient beta for proton transfer increases from 0.63 to 0.69 as the carboxylic acid is changed from dichloroacetic to acetic acid. The change in these Brønsted coefficients with changing reaction driving force, (inverted theta)alpha/ (inverted theta) deltaG(av) degrees=(inverted theta)beta/(inverted theta)delta G(av) degrees= 1/8lambda = 0.011, is used to calculate a Marcus intrinsic reaction barrier of lambda= 11 kcal/mol which is close to the barrier of 13 kcal/mol for thermoneutral proton transfer between this series of acids and bases. The value of alpha= 0.66 for thermoneutral proton transfer is greater than alpha= 0.50 required by a reaction that follows the Marcus equation. This elevated value of beta may be due to an asymmetry in the reaction coordinate that arises from the difference in the intrinsic barriers for proton transfer at the oxygen acid reactant and resonance-stabilized carbon acid product.

Dynamic Processes in the Copper-Catalyzed Substitution of Chiral Allylic Acetates Leading to Loss of Chiral Information

Copper-catalyzed alpha-substitution of enantiomerically pure secondary allylic esters with Grignard reagents was studied with the aim to find conditions that give racemic products. It was observed that the degree of chiral transfer is strongly dependent on the temperature. The loss of chiral information is consistent with an equilibration of the Cu(III)(allyl) intermediates prior to product formation. Equilibration of the reaction intermediates is of importance for a possible development of a dynamic kinetic asymmetric transformation (DYKAT) process, in which a chiral catalyst is used to produce an optically active product from a racemic substrate, by means of a dynamic equilibrium of the diastereomeric reaction intermediates.

Activity of essential oils from Brazilian medicinal plants on Escherichia coli

Essential oils obtained from leaves of 29 medicinal plants commonly used in Brazil were screened against 13 different Escherichia coli serotypes. The oils were obtained by water-distillation using a Clevenger-type system and their minimal inhibitory concentration (MIC) were determined by microdilution method. Essential oil from Cymbopogon martinii exhibited a broad inhibition spectrum, presenting strong activity (MIC between 100 and 500 microg/mL) against 10 out of 13 Escherichia coli serotypes: three enterotoxigenic, two enteropathogenic, three enteroinvasive and two shiga-toxin producers. C. winterianus inhibited strongly two enterotoxigenic, one enteropathogenic, one enteroinvasive and one shiga-toxin producer serotypes. Aloysia triphylla also shows good potential to kill Escherichia coli with moderate to strong inhibition. Other essential oils showed antimicrobial properties, however with a more restricted action against the serotypes studied. Chemical analysis of Cymbopogon martinii essential oil performed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC-MS) showed the presence of compounds with known antimicrobial activity, including geraniol, geranyl acetate and trans-cariophyllene, which tested separately, indicated geraniol as antimicrobial active compound. The significant antibacterial activity of Cymbopogon martinii oil suggests that they could serve as a source for compounds with therapeutic potential.

Achieving Augmented Limits of Detection for Peptides with Hydrophobic Alkyl Tags

The wide range of protein concentrations found in biological matrixes presents a formidable analytical challenge in proteomics experiments. It is predicted that low-abundance proteins are the likely clinically relevant targets in disease-based proteomics analyses. To effectively analyze low-abundance proteins by electrospray ionization mass spectrometry, limits of detection must be improved upon. Previous studies have demonstrated hydrophobicity is a main determinant of the electrospray ionization response. One would expect to improve the electrospray ionization response of a hydrophilic peptide by making it more hydrophobic, thus increasing the molecule's affinity for the surface of the electrospray droplet, thereby allowing the molecule to more effectively compete for charge. In this report, we demonstrate a strategy to increase the electrospray ionization response of cysteine-containing peptides with the addition of an octylcarboxyamidomethyl modification via alkylation chemistry, which we name the ALiPHAT strategy (augmented limits of detection for peptides with hydrophobic alkyl tags). We demonstrate the relative increase in electrospray ionization response of peptides with an octylcarboxyamidomethyl modification compared to carboxyamidomethyl-modified peptides upon LC-MS analysis. Furthermore, we show the octylcarboxyamidomethyl group does not fragment or undergo neutral loss during collision-induced dissociation. Collectively, our results demonstrate the feasibility of the octylcarboxyamidomethyl modification to improve limits of detection for cysteine-containing peptides.

Evidence for a Novel Binding Site Conformer of Aldose Reductase in Ligand-Bound State†

Human aldose reductase (ALR2) has evolved as a promising therapeutic target for the treatment of diabetic long-term complications. The binding site of this enzyme possesses two main subpockets: the catalytic anion-binding site and the hydrophobic specificity pocket. The latter can be observed in the open or closed state, depending on the bound ligand. Thus, it exhibits a pronounced capability for induced-fit adaptations, whereas the catalytic pocket exhibits rigid properties throughout all known crystal structures. Here, we determined two ALR2 crystal structures at 1.55 and 1.65 A resolution, each complexed with an inhibitor of the recently described naphtho[1,2-d]isothiazole acetic acid series. In contrast to the original design hypothesis based on the binding mode of tolrestat (1), both inhibitors leave the specificity pocket in the closed state. Unexpectedly, the more potent ligand (2) extends the catalytic pocket by opening a novel subpocket. Access to this novel subpocket is mainly attributed to the rotation of an indole moiety of Trp 20 by about 35 degrees . The newly formed subpocket provides accommodation of the naphthyl portion of the ligand. The second inhibitor, 3, differs from 2 only by an extended glycolic ester functionality added to one of its carboxylic groups. However, despite this slight structural modification, the binding mode of 3 differs dramatically from that of the first inhibitor, but provokes less pronounced induced-fit adaptations of the binding cavity. Thus, a novel binding site conformation has been identified in a region where previous complex structures suggested only low adaptability of the binding pocket. Furthermore, the two ligand complexes represent an impressive example of how the slight change of a chemically extended side-chain at a given ligand scaffold can result in a dramatically altered binding mode. In addition, our study emphasizes the importance of crystal structure analysis for the translation of affinity data into structure-activity relationships.

Regio- and stereoselective anomeric esterification of glucopyranose 1,2-diols and a facile preparation of 2-O-acetylated glucopyranosyl trichloroacetimidates from the corresponding 1,2-diols

A highly regio- and stereoselective anomeric esterification of 3-O-allyl (or benzyl, or benzoyl)-4,6-O-isopropylidene-alpha,beta-d-glucopyranose with acetyl chloride, or allyl chloroformate, or ethyl chloroformate gave the corresponding 2-OH, 1-beta-acetates or -carbonates in excellent yields. The 2-OH, 1-beta-acetates were readily converted to the corresponding 2-O-acetylated glucopyranosyl trichloroacetimidates by reaction with trichloroacetonitrile via base promoted acetyl migration, while the 2-OH, 1-beta-carbonates were good glycosyl acceptors for the synthesis of (1-->2)-linked oligosaccharides.

Structural Study of Polymorphs and Solvates of Finasteride

NMR and XRD data are reported for several new forms of finasteride, including the results of complete structure determinations for three solvates. Form III of finasteride, hitherto only mentioned in the patent literature, and a new anhydrous form designated Form X, have been found in mixtures of polymorphs and their (13)C NMR chemical shifts obtained. The results demonstrate that the crystallographic asymmetric units contain three molecules and one molecule, respectively. Attempts to reproduce "Form H1", as described in a patent, resulted in a new IPA solvate hydrate. The previously-reported acetic acid, dioxane, and ethyl acetate solvates have been further characterised, and new THF and diethyl ether solvates prepared and characterised. The crystal structures of the dioxane, IPA, and THF solvates have been determined by single-crystal X-ray diffraction. All the solvates (except the acetic acid case) are found to be hemihydrates, to have a finasteride: solvent molar ratio of 2:1 and to have a common structure. The solvate molecules are highly disordered and sited in channels in the structure. The powder XRD patterns are characteristic of the common structure. These solvates may be distinguished by the characteristic CPMAS (13)C signals from the solvent molecules, but the resonances of the host finasteride structures differ only marginally, and powder XRD patterns are almost indistinguishable. Magic-angle spinning (MAS) proton spectra give sharp lines for the solvent peaks, confirming their high degree of mobility. This is further shown in one case by direct polarisation (13)C spectra. Mobility of the tert-butyl group is also implied. Thermal characteristics have been studied and TGA used (in conjunction with solution-state proton NMR) to estimate molar ratios.