2-Amino-2-Oxazolines,Part VIII. Calculated Molecular Properties of Tautomeric Species

The geometries, tautomerization energies, and dipole moments of the tautomeric species of the 2-amino-2-oxazoline heterocycle were calculated with full geometry optimization using semiempirical (MNDO, AM1 and PM3) and ab initio (RHF/6–31G) methods. The planar conformation of the amino form is well reproduced by the semiempirical and by the ab initio methods as compared with X-ray structures in which this form is found. However the exocyclic nitrogen atom is pyramidalized in the semiempirical geometries whereas the ab initio method reproduces a sp² hybridization state. The twisted conformation of the imino form is better reproduced by the ab initio calculation. All methods (semiempirical and ab initio) show a stability energy value in favour of the amino tautomer of the neutral heterocycle. On the contrary, the dominant species of the charged heterocycle is the imino tautomer, protonated on the exocyclic nitrogen atom. Molecular electrostatic potential calculations confirmed this tendency. Finally the 3D-lipophilicity profile of the heterocycle completed the investigation of the tautomerism.     

2-Aminooxazolines, I: Crystal and molecular structure of 5-(1-aryl-4-piperazino)methyl-substituted derivatives with antidepressant activity

The structure of two 5-(1-aryl-4-piperazino)methyl-2-aminooxazolines were determined by X-ray crystallography. An amino form is preponderant in a free base whereas an imino form is preponderant in a salt. The molecular conformations were studied by molecular mechanics.     

Mass Spectra of Amides of 2-Amino-2-thiazoline

Five fragmentation patterns of the molecular ions of sixteen amides of 2-amino-2-thiazoline and of one deuteriophenyl derivative are described: when R is a phenyl group substituted in ortho position by an R″ group, the [M-R″]⁺ ion is the main fragment, whereas in the other cases R″ = substituent in meta or para position it is the ion [M-H]⁺. The amino?imino tautomerism of these molecular ions was studied. In addition, a correlation was found between the fragmentation patterns of the molecules and their pharmacological activities.     

Ranitidine Hydrochloride-loaded Ethyl Cellulose and Eudragit RS 100 Buoyant Microspheres: Effect of pH Modifiers

A floating type of dosage form of ranitidine hydrochloride in the form of microspheres capable of floating on simulated gastric fluid was prepared by solvent evaporation technique. Microspheres prepared with ethyl cellulose, Eudragit^® RS100 alone or in combination were evaluated for percent yield, drug entrapment, percent buoyancy and drug release and the results demonstrated satisfactory performance. Microspheres exhibited ranitidine hydrochloride release influenced by changing ranitidine hydrochloride-polymer and ranitidine hydrochloride-polymer-polymer ratio. Incorporation of a pH modifier has been the usual strategy employed to enhance the dissolution rate of weakly basic drug from floating microspheres. Further citric acid, fumaric acid, tartaric acid were employed as pH modifiers. Microspheres prepared with ethyl cellulose, Eudragit^® RS100 and their combination that showed highest release were utilized to study the effect of pH modifiers on ranitidine hydrochloride release from microspheres which is mainly affected due to modulation of microenvironmental pH. In vitro release of ranitidine hydrochloride from microspheres into simulated gastric fluid at 37° showed no significant burst effect. However the amount of release increased with time and significantly enhanced by pH modifiers. 15% w/w concentration of fumaric acid provide significant drug release from ranitidine hydrochloride microspheres prepared with ranitidine hydrochloride:ethyl cellulose (1:3), ranitidine hydrochloride:Eudragit^® RS100 (1:2) and ranitidine hydrochloride:ethyl cellulose:Eudragit^® RS100 (1:2:1) whereas citric acid, tartaric acid showed significant cumulative release at 20% w/w. In all this study suggest that ethyl celluose, Eudragit^® RS100 alone or in combination with added pH modifiers can be useful in floating microspheres which can be proved beneficial to enhance the bioavailability of ranitidine hydrochloride.     

Zur Oxidation von 2,5-Dihydroxyphenylethylamin-Derivaten

Oxidation of 2,5-Dihydroxyphenylethylamine Derivatives The syntheses of the free bases 1c , 1f and 11b , their hydrochlorides and the acetyl derivatives 12a and 12b are described. Treatment of the 2,5-dihydroxyphenylethylamine derivatives 1c and 1f with catalytical amounts of oxidants affords the indolines 5c and 5f . Compound 5c is characterised as hydrochloride, diacetate 13a and monoacetate 5g . Indoline 5f is synthesized as base and hydrochloride and transformed to the monoacetate 13b . The structures are analysed by MS, ¹H-NMR and ¹³C-NMR spectroscopy. The course of the reaction that leads to the indolines 5 is discussed.     

An efficient synthesis and antioxidant properties of novel imino and amino derivatives of 4-hydroxy coumarins

Series of imino and amino derivatives of 4-hydroxy coumarins were synthesized via conventional and microwave promoted procedure and evaluated for antioxidant potential through different in vitro models such as (DPPH) free radical scavenging activity, linoleic acid emulsion model system, reducing power assay and phosphomolybdenum method. All prepared compounds possess good antioxidant activity and among them p-nitro-phenyl derivative 6c with IC₅₀ at 25.9 μM possesses radical scavenging activity which is comparable to standard BHT, while the best reducing power was observed in a case of benzyl amino compound 8c (RP₅₀ 255.6 μM). Also, observed data indicated that compounds may serve as inhibitors of lipid peroxidation process.     

Synthesis of 4‐thia[5‐13C]lysine

This report describes the synthesis of 4‐thia[5‐¹³C]lysine, an isotopomer of 4‐thialysine that is an analog of lysine. It was synthesized from 2‐amino[1‐¹³C]ethanol hydrochloride (1) in two steps. In the first step, 1 was converted to 2‐bromo[2‐¹³C]ethylamine hydrobromide (2). The reaction of cysteine with 2 in basic condition followed by acidification afforded 4‐thia[5‐¹³C]lysine hydrochloride (3).     

Synthesis and Antitubercular Activity of 2‐(substituted phenyl/benzyl‐amino)‐6‐(4‐chlorophenyl)‐5‐(methoxycarbonyl)‐4‐methyl‐3,6‐dihydropyrimidin‐1‐ium Chlorides

A series of 2‐(substituted phenyl/benzyl‐amino)‐6‐(4‐chlorophenyl)‐5‐(methoxycarbonyl)‐4‐methyl‐3,6‐dihydropyrimidin‐1‐ium chlorides 7–13 and 15 was synthesized in their hydrochloride salt form. The title compounds were characterized by FT‐IR, NMR (¹H and ¹³C) and elemental analysis. They were evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv, multidrug resistance tuberculosis and extensively drug resistance tuberculosis by agar diffusion method and tested for the cytotoxic action on peripheral blood mononuclear cells by MTT assay. Among all the tested compounds in the series, compounds 7 and 11 emerged as promising antitubercular agents at 16 μg/mL against multidrug resistance tuberculosis and over 64 μg/mL against extensively drug resistance tuberculosis. The conformational features and supramolecular assembly of the promising compounds 7 and 11 were determined by single crystal X‐ray study.     

Guanidinium-carboxylate interaction: methylguanidinium formate

The crystal structure of methylguanidinium formate is presented as a model for arginine - carboxylate interactions. The crystals are orthorhombic, P2₁2₁2₁, with a =6.963(2), b = 7.110(2), c = 11.873(3)Å. The structure was solved by direct methods and refined by block-diagonal least squares to R = 0.078 and R_w = 0.080. Ion pairs are formed by hydrogen bonds between the amino and CH³ NH- imino groups and the formate ion. Additional hydrogen bonding results in the formation of a three-dimensional network. Comparisons are made with similar compounds.     

Influence of the Solid Form of Siramesine Hydrochloride on its Behavior in Aqueous Environments

Purpose  To study the influence of solid form on the behavior of the salt siramesine hydrochloride in aqueous environments. Methods  The solubilities and dissolution rates of siramesine hydrochloride anhydrate and monohydrate were determined at pH 3.4 and 6.4, and precipitates were examined by X-ray powder diffraction. The mechanism of anhydrate–hydrate conversion was investigated by optical microscopy, and wet massing of the anhydrate was carried out using water and 60% (v/v) ethanol separately as granulation liquids. The wet masses were analyzed using Raman microscopy. Results  At pH 3.4 the anhydrate and monohydrate salts exhibited similar dissolution profiles. At pH 6.4 both the anhydrate and monohydrate salts formed supersaturated solutions of high apparent solubility. From the anhydrate solution, precipitation of the free base occurred, while the solution of the monohydrate salt remained in the supersaturated state. This resulted in a superior dissolution profile of the monohydrate salt. Microscopy and wet massing experiments showed that the anhydrate–hydrate conversion of siramesine hydrochloride was solution-mediated and dissolution-controlled. Conclusion  During development of a formulation based on the anhydrate salt, the risk of processing-induced transformation to the monohydrate form as well as precipitation of the free base should be considered.     

硫酸沙丁胺醇的合成研究Ⅰ

以水杨醛与叔丁胺为起始原料，经缩合、酯化、Ｆｒｉｅｓ重排三步一锅反应制成２－氯－１－｛［（１，１－二甲基乙基）亚胺基甲基］－４－羟基苯基｝－乙基酮（４）．再经缩合、水解、成盐三步一锅反应转化成５－｛［（１，１－二甲基乙基）胺基］乙酰基｝－２－羟基苯甲醛盐酸盐（５），再经甲醇钠中和、催化转移氢化还原、成盐即得硫酸沙丁胺醇（１），总收率约５０％。     

Effects of cortisol and tetrahydrocortisol on the cloned fibroblast derived from rat carrageenin granuloma

A fibroblast clone SM-Cl was established by cloning cultured fibroblasts derived from a rat carrageenin granuloma. The cloned fibroblasts were found to produce and secrete large amounts of acidic glycosaminoglycans (AGAG) and collagen into the medium, and the AGAG were identified with chondroitin 4-sulfate and hyaluronic acid by 2-dimensional electrophoresis and enzymatic digestion. The cells were exposed to 10^?6M cortisol or 10^?4M tetrahydrocortisol for 2 days during their stationary phase. The amounts of AGAG and collagen secreted into the medium, the protein and RNA contents of the cells, the amounts of free amino acids per 10⁹ cells, the intracellular concentration of each free amino acid, and the distribution ratio (ratio of intracellular concentration to that in the medium) of each free amino acid of the cells were compared with those of control cells. The production of intracellular substances was markedly inhibited by cortisol, i.e., by 75 per cent for AGAG and by 50 per cent for collagen. Both the amount of each amino acid per 10⁹ cells and the distribution ratios were markedly depressed by cortisol treatment for all the determined amino acids except serine. The cloned fibroblasts were then studied with regard to the rate of uptake of 2-amino[1-¹⁴C]isobutyric acid (AIB) from the medium by control and steroid-treated cells. Cortisol treatment decreased [¹⁴C]AIB uptake of the cell markedly from the beginning up to 90 min of incubation. Tetrahydrocortisol, one of the main metabolites of cortisol, exerted no effect even at a concentration as high as 10^?4 M.Incorporation of [³H]thymidine into DNA of the cells in the growing phase was affected very slightly by the drugs.     

Carbonic anhydrase inhibitors. Synthesis of water-soluble, topically effective, intraocular pressure-lowering aromatic/heterocyclic sulfonamides containing cationic or anionic moieties: is the tail more important than the ring?

Reaction of several aromatic/heterocyclic sulfonamides containing a free amino, imino, hydrazino, or hydroxyl group, with 2, 3-pyridinedicarboxylic anhydride or 2,6-pyridinedicarboxylic acid in the presence of carbodiimide derivatives, afforded two series of water-soluble (as hydrochloride, triflate, or carboxylate salts) compounds. The new derivatives were assayed as inhibitors of the zinc enzyme carbonic anhydrase (CA) and more precisely of three of its isozymes, CA I, II (cytosolic forms), and IV (membrane-bound form), involved in important physiological processes. Efficient inhibition was observed against all three isozymes, but especially against CA II and IV (in nanomolar range), the two isozymes known to play a critical role in aqueous humor secretion within the ciliary processes of the eye. Some of the best inhibitors synthesized were applied as 2% water solutions directly into the eye of normotensive and glaucomatous albino rabbits. Very strong and long-lasting intraocular pressure (IOP) lowering was observed with many of them. This result prompted us to reanalyze the synthetic work done by other groups for the design of water-soluble, topically effective antiglaucoma sulfonamides. According to these researchers, the IOP-lowering effect is due to the intrinsic nature of the specific heterocyclic sulfonamide considered, among which the thienothiopyran-2-sulfonamide derivatives represent the best-studied case. Indeed, the first agents developed for topical application, such as dorzolamide, are derivatives of this ring system. To prove that the tail (in this case the pyridinecarboxylic moieties) conferring water solubility to a sulfonamide CA inhibitor is more important than the ring to which the sulfonamido group is grafted, we also prepared dorzolamide derivatives incorporating such moieties. These new compounds possess good water solubility as hydrochloride or carboxylate salts, balanced by a relatively modest lipid solubility. They are strong CA II inhibitors and are able to lower IOP in experimental animals more than the parent derivatives. Our conclusion is that the tail conferring water solubility to such an enzyme inhibitor is more important for topical activity as an antiglaucoma drug, than the heterocyclic/aromatic ring to which the sulfonamido moiety is grafted.     

Carbonic anhydrase inhibitors. Part 71: Synthesis and ocular pharmacology of a new class of water-soluble, topically effective intraocular pressure lowering sulfonamides incorporating picolinoyl moieties

Reaction of 20 aromatic/heterocyclic sulfonamides containing a free amino, imino, hydrazino or hydroxyl group, with picolinic acid in the presence of carbodiimide derivatives afforded a series of water-soluble (as hydrochloride or triflate salts) compounds. The new derivatives were assayed as inhibitors of three carbonic anhydrase (CA) isozymes, CA I, II (cytosolic forms) and IV (membrane-bound form). Efficient inhibition was observed against all three isozymes, but especially against CA II and CA IV (in nanomolar range), the two isozymes known to play a critical role in aqueous humor secretion within the ciliary processes of the eye. Some of the best inhibitors synthesized were applied as 2% water solutions directly into the eye of normotensive or glaucomatous albino rabbits. Very strong intraocular pressure (IOP) lowering was observed for many of them, and the active drug was detected in eye tissues and fluids. This result prompted us to reanalyze the synthetic work done by other groups for the design of water soluble, topically effective antiglaucoma sulfonamides. According to these researchers, the IOP lowering effect is due to the intrinsic nature of the specific heterocyclic sulfonamide considered, among which the thienothiopyran-2-sulfonamide derivatives represent the best studied case. Indeed, the first agents developed for such applications, such as dorzolamide, are derivatives of this ring system. In order to prove that the tail (in this case the picolinoyl moiety) conferring water solubility to a sulfonamide CA inhibitor is critically important for its topical effectiveness, similarly to the ring to which the sulfonamido group is grafted, we also prepared a dorzolamide derivative to which the picolinoyl moiety was attached. This new compound is more water soluble than dorzolamide (as hydrochloride salt), behaves as a strong CA II inhibitor, and acts similarly to the parent derivative in lowering IOP in experimental animals. Thus, it seems that the tail conferring water solubility is more important for topical activity as antiglaucoma drug, than the heterocyclic/aromatic ring to which the sulfonamido moiety is grafted.     

Biowaiver Monograph for Immediate-Release Solid Oral Dosage Forms: Ondansetron

Literature data pertaining to the physicochemical, pharmaceutical, and pharmacokinetic properties of ondansetron hydrochloride dihydrate are reviewed to arrive at a decision on whether a marketing authorization of an immediate release (IR) solid oral dosage form can be approved based on a Biopharmaceutics Classification System (BCS)-based biowaiver. Ondansetron, a 5HT₃ receptor antagonist, is used at doses ranging from 4 mg to 24 mg in the management of nausea and vomiting associated with chemotherapy, radiotherapy, and postoperative treatment. It is a weak base and thus exhibits pH-dependent solubility. However, it is able to meet the criteria of “high solubility” as well as “high permeability” and can therefore be classified as a BCS class I drug. Furthermore, ondansetron hydrochloride 8 mg IR tablets (Zofran^® 8 mg) and multiples thereof (16 mg = Zofran^® 8 mg × 2 tablets and 24 mg = Zofran^® 8 mg × 3 tablets) meet the criteria of “rapidly dissolving” in dissolution testing. Ondansetron hydrochloride has a wide therapeutic window and is well-tolerated after oral administration. Based on its favorable physicochemical properties, pharmacokinetic data and the minimal risks associated with an incorrect bioequivalence decision, the BCS-based biowaiver procedure can be recommended for ondansetron hydrochloride dihydrate IR tablets.     

Development and Validation of a HPTLC Method for Simultaneous Quantitation of Flunarizine Dihydrochloride and Propranolol Hydrochloride in Capsule Dosage Form

A simple, precise, accurate, and rapid high-performance thin layer chromatographic method has been developed and validated for the simultaneous quantitation of flunarizine dihydrochloride and propranolol hydrochloride in a combined capsule dosage form. The method was carried out on precoated silica gel 60 F₂₅₄ TLC aluminum plate, (20×10 cm²). The solvent system was ethyl acetate:methanol:glacial acetic acid in the proportion of 8:1:1, (v/v/v). R_f value for flunarizine dihydrochloride and propranolol hydrochloride was found to be 0.62±0.02 and 0.18±0.02, respectively. The linearity regression analysis for calibration showed 0.999 and 0.999 for flunarizine dihydrochloride and propranolol hydrochloride with respect to peak area and height in the concentration range of 50-350 ng/spot and 500-3500 ng/spot, respectively. Accuracy of recovery studies was found to be 98-100.28 and 99.11-99.45% for flunarizine dihydrochloride and propranolol hydrochloride, respectively. The amounts of drug in marketed formulation were 100.5 and 101.25% of flunarizine dihydrochloride and propranolol hydrochloride, respectively. The method developed can be used for routine analysis in bulk drug and capsule dosage form.     

Synthesis of polyamide supports for use in peptide synthesis and as peptide-resin conjugates for antibody production

We have synthesized beaded, hydrophilic cross-linked, aminoalkyl polydimethylacrylamide supports upon which peptides have been assembled using standard Boc or Fmoc chemistry in automated equipment. The resins were prepared by the free radical-initiated co-polymerization of N,N-dimethylacrylamide, N,N′-bisacrylyl-1,3-diaminopropane, and a functional monomer which were contained in a reverse-phase, detergent-emulsified suspension. The functional monomers used were N-(2-(methylsulfonyl)ethyloxycarbonyl)-allyl-amine (MSC-allylamine), N-acrylyl-1,6-diaminohexane hydrochloride or N-methacrylyl-1,3-diaminopropane hydrochloride. The MSC protecting group was removed by treatment of the resin with methanolic base during workup. After coupling of N-α-t-butyloxycarbonyl-alanine (Boc-alanine), amino acid analyses gave resin loading capacities between 0.15 mmol/g and 1.4 mmol/g, depending on the concentration and composition of the functional monomer. The resulting polymers were highly swollen by polar solvents including aqueous buffers. Peptides were synthesized on these supports after attaching the first amino acid directly or through a cleavable ester linker. When the carboxyl-terminal amino acid was coupled as the 4-oxymethylbenzoic acid derivative, the peptide could be deprotected and remain attached to the hydrophilic polymer since the peptide-benzyl ester bond was stable to HF deprotection at 0° in the presence of 10% anisole and 1% ethanedithiol. The resulting peptidyl-resin could be swollen in aqueous buffers and injected into animals for the production of antibodies.     

DES—Nα1—ACETYL—α—MELANOTROPIN:

Application of the 2-methylsulfonylethyloxycarbonyl group for temporary amino protection enables the synthesis from one precursor of des-Nα¹-acetyl-α-MSH, the two mono N-acetylated forms (in positions I and II) and the diacetyl form of this tridecapeptide amide. The free tridecapeptide amide, although structurally unrelated to the normal substrate, was recognized by an enzyme occurring in calf eye-lens tissue. The product of the enzymatic reaction was exclusively α-MSH. Partial sequences derived from the N-terminus were less rapidly acetylated or not at all, depending on their chain length. The enzyme, therefore, appears to direct its activity to free N-terminal α-amino groups of peptides exceeding a certain critical chain length. Acetylation of -amino functions did not occur.     

Physical characterization of carteolol: Eudragit® L binding interaction

Eudragit® L 30D was used as a carrier to prepare carteolol polymeric complexes in order to obtain controlled release dosage forms. The polyanionic form of the polymer, neutralized at different degrees, reacts readily with carteolol hydrochloride to give water-insoluble complexes. Carteolol complexes were characterized by differential scanning calorimetry, IR, ¹H- and ¹³C-NMR spectroscopy. In fact, results indicated that there were intermolecular associations between the polymer and the drug consisting in ammonium salt interactions. Maximum carteolol content was found to be 22% in the complexes.