Synthesis of deuterium-labeled 16 alpha,19-dihydroxy C19 steroids as internal standards for gas chromatography-mass spectrometry.

[2 beta,7,7,16 beta-2H4]16 alpha,19-Dihydroxyandrost-4-ene-3,17-dione (14) and [7,7,16 beta-2H3]3 beta,16 alpha,19-trihydroxyandrost-5-en-17-one (16), with high isotopic purity, respectively, were synthesized from unlabeled 3 beta-(tert-butyldimethylsiloxy)-androst-5-ene-17 beta-yl acetate (1). The deuterium introduction at C-7 was carried out by reductive deoxygenation of the 7-keto compound 3 with dichloroaluminum deuteride and that at C-2 beta and/or C-16 beta by controlled alkaline hydrolysis of 16-bromo-17-ketone 11 or 12 with NaOD in D2O and pyridine. [7,7-2H2]3 beta-Hydroxyandrost-5-en-17-one (6), obtained from compound 1 by a five-step sequence, was converted to compound 14 or 16 by an eight-step or seven-step sequence, respectively. The labeled steroids 14 and 16 are useful as internal standards for gas chromatography-mass spectrometry analysis of the endogenous levels.     

Improved synthesis and molecular modeling of 4beta,19-dihydroxyandrost-5-en-17-one,an excellent inhibitor of aromatase

4Beta,19-dihydroxyandrost-5-en-17-one (6) is an excellent competitive inhibitor of estrogen synthetase (aromatase). Alternate, improved synthesis of this inhibitor was established. Treatment of 19-(tert-butyldimethylsilyloxy)androst-4-en-17-one (8) with m-chloroperbenzoic acid gave a 1.4:1 mixture of 4alpha,5alpha-epoxide 9 and its 4beta,5beta-isomer 10. The mixture was reacted with diI. HClO4 in dioxane to produce principally 4beta,5alpha-diol 11 (80%) of which acetylation followed by dehydration with SOCl2 yielded 4beta,19-diacetoxy-5-ene compound 14 in good yield. Alkaline hydrolysis of diacetate 14 gave 4beta,19-diol 6. The minimum energy conformation of the powerfull aromatase inhibitor 6 was obtained with the PM3 method and compared with that of the structurally related diol steroid, 4-ene-5beta,19-diol 3, a weak competitive inhibitor.     

Total synthesis and absolute configuration of liverwort diterpenes, (-)-13(15)E,16E-3beta,4beta-epoxy-18-hydroxysphenoloba-13(15),16-diene and (-)-13(15)Z,16E-3beta,4beta-Epoxy-18-hydroxysphenoloba-13(15),16-diene,by use of the ring closing metathesis reaction applied to seven-membered carbocycles with a trisubstituted double bond

Seven-membered cyclic compounds possessing trisubstituted double bonds have been effectively constructed employing the Grubbs catalyst to effect olefin metathesis. The keto ester does not undergo cyclization; however, alcohols protected by the silyl groups smoothly cyclized into seven-membered compounds. The product was successfully converted to (-)-13(15)E,16E-3beta,4beta-epoxy-18-hydroxysphenoloba-13(15),16-diene and (-)-13(15)Z,16E-3beta,4beta-epoxy-18-hydroxysphenoloba-13(15),16-diene, liverwort diterpenes isolated from Anastrophyllum auritum to establish the absolute configuration.     

Kinetic coupled with UV spectral evidence for near-irreversible nonionic micellar binding of N-benzylphthalimide under the typical reaction conditions: an observation against a major assumption of the pseudophase micellar model

Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of N-benzylphthalimide (1) show a nonlinear decrease with the increase in [C(m)E(n)]T (total concentration of Brij 58, m = 16, n = 20 and Brij 56, m = 16, n = 10) at constant [CH(3)CN] and [NaOH]. These nonionic micellar effects, within the certain typical reaction conditions, have been explained in terms of the pseudophase micellar (PM) model. The values of micellar binding constants (KS) of 1 are 1.04 x 10(3) M(-1) (at 1.0 x 10(-3) M NaOH) and 1.08 x 10(3) M(-1) (at 2.0 x 10(-3) M NaOH) for C(16)E(20) as well as 600 M(-1) (at 7.6 x 10(-4) M NaOH) and 670 M(-1) (at 1.0 x 10(-3) M NaOH) for C(16)E(10) micelles. The pseudo-first-order rate constants (kM) for hydrolysis of 1 in C(16)E(20) micellar pseudophase are approximately 90-fold smaller than those (kW) in water phase. The values of kM for hydrolysis of 1 in C(16)E(10) micelles are almost zero. Kinetic coupled with UV spectral data reveals significant irreversible nonionic micellar binding of 1 molecules in the micellar environment of nearly zero hydroxide ion concentration at >or=0.14 M C(16)E(20) and 1.0 x 10(-3) M NaOH while such observations could not be detected at or=3 x 10(-3) M C(16)E(10) and 7.6 x 10(-4) M NaOH, while the rate of hydrolysis of 1 is completely ceased at >or=0.05 M C(16)E(10) and 7.6 x 10(-4) M NaOH. The rate of hydrolysis of 1 at 5.0 x 10(-2) and 8.8 x 10(-2) M C(16)E(10) and 1.0 x 10(-3) M NaOH reveals the formation of presumably phthalic anhydride, whereas such observation was not observed in the C(16)E(20) micellar system under similar experimental conditions.     

Hydrolysis of 2',3'-O-methyleneadenos-5'-yl bis(2',5'-di-O-methylurid-3'-yl) phosphate, a sugar O-alkylated trinucleoside 3',3',5'-monophosphate: implications for the mechanism of large ribozymes

Hydrolytic reactions of 2',3'-O-methyleneadenos-5'-yl bis(2',5'-di-O-methylurid-3'-yl) phosphate (1), a sugar O-alkylated trinucleoside 3',3',5'-monophosphate, have been followed by RP HPLC over a wide pH range. Under neutral and mildly acidic conditions, the only reaction observed was a pH-independent cleavage of the O-C5' bond of the 5'-linked nucleoside. Under more alkaline conditions nucleophilic attack by hydroxide ion starts to compete. The reaction is first order in [OH(-)] and becomes predominant at pH 10. Each of the 3'-linked nucleosides is displaced 2.9 times as readily as the 5'-linked one. To determine the beta(lg) value for the hydroxide ion catalyzed hydrolysis of 1, two diesters (2a,b) having 2',3'-O-methyleneadenosine (7) and 2',5'-di-O-methyluridine (4) as leaving groups were hydrolyzed under alkaline conditions. Since the beta(lg) value for this reaction is known, DeltapK(a) between 4 and 7 could be calculated. The beta(lg) for the hydrolysis of 1 was estimated to be -0.5 with use of this information. The mechanisms of the partial reactions and the role of leaving group properties in ribozyme reactions of large ribozymes are discussed.     

Epoxidation and reduction of DHEA, 1,4,6-androstatrien-3-one and 4,6-androstadien-3beta,17beta-diol

Dehydroepiandrosterone (DHEA) reacted with m-chloroperoxybenzoic acid(m-CPBA) to form 3beta-hydroxy-5alpha,6alpha-epoxyandrostan-17-one (1), but it did not react with 30% H2O2. 1,4,6-Androstatrien-3,17-dione (2) was obtained from DHEA and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in dioxane. Compound 2 was reacted with 30%H2O2 and 5% NaOH in methanol to give 1alpha,2alpha-epoxy-4,6-androstadien-3,17-dione (3),which was stereoselectively reduced with NaBH4 to form 1alpha,2alpha-epoxy-4,6-androstadien-3beta,17beta-diol (7) and reacted with Li metal in absolute ethanol-tetrahydrofuran mixture to give 2-ethoxy-1,4,6-androstatrien-3,17-dione (8). Compound 2 was also epoxidized with m-CPBA in dichloromethane to afford 6alpha,7alpha-epoxy-1,4-androstadien-3,17-dione (4),which was reacted with NaBH4 to synthesize 6alpha,7alpha-epoxy-4-androsten-3beta,17beta-diol (9).Compound 4 was reduced with Li metal in absolute ethanol-tetrahydrofuran mixture to form 7beta-ethoxy-6alpha-hydroxy-1,4-androstadien-3,17-dione (10). Compound 2 was reduced with NaBH4 in absolute ethanol to form 4,6-androstadien-3beta,17beta-diol (5), which was reacted with 30% H2O2 to give the original compound, but which reacted with m-CPBAto give 4beta,5beta-epoxy-6-androsten-3beta,17beta-diol (6).     

A cytotoxic and apoptosis-inducing sesquiterpenoid isolated from the aerial parts of Artemisia princeps PAMPANINI (Sajabalssuk)

Repeated silica gel and octadecyl silica gel (ODS) column chromatography of the aerial parts of Artemisia princeps PAMPANINI (Sajabalssuk) led to the isolation of a new sesquiterpenoid, 3-((S)-2-methylbutyryloxy)-costu-1(10),4(5)-dien-12,6 alpha-olide (2), along with two previously reported sesquiterpenoids: 8 alpha-angeloyloxy-3beta,4 beta-epoxy-6 beta H,7 alpha H,8 beta H-guaia-1(10),11(13)-dien-12,6 alpha-olide (1, carlaolide B) and 3beta,4 beta-epoxy-8 alpha-isobutyryloxy-6 beta H,7 alpha H,8 beta H-guaia-1(10),11(13)-dien-12,6 alpha-olide (3, carlaolide A). The structure of compound 2 was elucidated by spectroscopic data analysis, including one dimensional (1D) and two dimensional (2D) nuclear magnetic resonance (NMR) experiments. Of the isolates, compound 2 exhibited potent cytotoxicity against human cervix adenocarcinoma cells and induced apoptosis.     

Kinetics and mechanism of large rate enhancement in the alkaline hydrolysis of N'-morpholino-N-(2'-methoxyphenyl)phthalamide

The apparent second-order rate constant (k OH) for hydroxide-ion-catalyzed conversion of 1 to N-(2'-methoxyphenyl)phthalamate (4) is approximately 10(3)-fold larger than k OH for alkaline hydrolysis of N-morpholinobenzamide (2). These results are explained in terms of the reaction scheme 1 --> k(1obs) 3 --> k(2obs) 4 where 3 represents N-(2'-methoxyphenyl)phthalimide and the values of k(2obs)/k(1obs) vary from 6.0 x 10(2) to 17 x 10(2) within [NaOH] range of 5.0 x 10(-3) to 2.0 M. Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of 1 decrease from 21.7 x 10(-3) to 15.6 x 10(-3) s(-1) with an increase in ionic strength (by NaCl) from 0.5 to 2.5 M at 0.5 M NaOH and 35 degrees C. The values of k obs, obtained for alkaline hydrolysis of 2 within [NaOH] range 1.0 x 10(-2) to 2.0 M at 35 degrees C, follow the relationship k(obs) = kOH[HO(-)] + kOH'[HO (-)] (2) with least-squares calculated values of kOH and kOH' as (6.38 +/- 0.15) x 10(-5) and (4.59 +/- 0.09) x 10(-5) M (-2) s(-1), respectively. A few kinetic runs for aqueous cleavage of 1, N'-morpholino-N-(2'-methoxyphenyl)-5-nitrophthalamide (5) and N'-morpholino-N-(2'-methoxyphenyl)-4-nitrophthalamide (6) at 35 degrees C and 0.05 M NaOH as well as 0.05 M NaOD reveal the solvent deuterium kinetic isotope effect (= k(obs) (H 2) (O)/ k(obs) (D 2 ) (O)) as 1.6 for 1, 1.9 for 5, and 1.8 for 6. Product characterization study on the cleavage of 5, 6, and N-(2'-methoxyphenyl)-4-nitrophthalimide (7) at 0.5 M NaOD in D2O solvent shows the imide-intermediate mechanism as the exclusive mechanism.     

Facile method for the preparation of lyso-GM1 and lyso-GM2

This paper reports a facile method for the preparation of lyso-GM1 [Gal beta1-->3GalNAc beta1--> 4(Neu5Ac alpha2-->3)Galbeta1-->4Glc beta1-->1'-sphingosine] and lyso-GM2 [GalNAc beta1-->4(Neu5Ac alpha2-->3)Gal beta1-->4Glc beta1-->sphingosine], respectively, from GM1 [Galbeta1-->3GalNAc beta1-->4(Neu5Ac alpha2-->3)Galbeta1-->4Glc beta1-->1'-Cer] and GM2[GalNAc beta1-->4(Neu5Ac alpha2-->3)Galbeta1-->4Glc beta1-->1'-Cer], using sphingolipid ceramide deacylase and high performance anion-exchange chromatography (HPAEC). The enzymatically released lyso-GM1 and/or lyso-GM2 was effectively separated from its parent ganglioside by HPAEC using a Mono Q HR 5/5 column with an Amersham Biosciences fast protein liquid chromatography system. The yield was almost quantitative and the separation completed in approximately 3 h. This method is more convenient and effective than the conventional method using alkaline hydrolysis and silicic acid chromatography to generate and purify lyso-gangliosides.     

Synthesis of 16 alpha-hydroxyandrost-4-ene-3,17,19-trione and 3 beta, 16 alpha-dihydroxyandrost-5-ene-17,19-dione; potential intermediates of estriol biosynthesis

16 alpha-Hydroxyandrost-4-ene-3,17,19-trione (10) was synthesized from the 16 alpha-hydroxy-6 beta,19-epoxy-17-one 3 via protection of the 16 alpha-hydroxy function as its tert-butyldimethylsilyl ether or acetate. Reductive cleavage of the epoxy ring of the silyl ether 4 or the acetate 5 with zinc dust gave the 19-alcohol 6 or 7, which was treated with pyridinium dichromate or Jones reagent, respectively, and then hydrolyzed with diluted sulfuric acid, yielding the desired steroid 10. 3 beta,16 alpha-Dihydroxyandrost-5-ene-17,19-dione (14) was also synthesized from 5 alpha-bromo-3 beta,16 alpha-diacetoxy-6 beta, 19-epoxyandrostan-17-one (11) through the intermediates 12 and 13 with the 3 beta- and 16 alpha-hydroxy functions protected as their acetates in a reaction sequence similar to that above.     

Synthesis and hydrolysis of a cis-chlorohydrin derived from a benzo[a]pyrene 7,8-diol 9,10-epoxide

(+/-)-7beta,8alpha-Dihydroxy-9beta,10beta-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (DE-1) undergoes reaction with anhydrous HCl in dioxane to yield predominantly ( approximately 94%) a single chlorohydrin. This chlorohydrin was assigned structure 9, in which the chloro goup at C-10 is located cis to the C-9 hydroxyl group, on the basis of its (1)H NMR spectrum. This result is in contrast to the reaction of a diastereomeric benzo[a]pyrene 7,8-diol 9,10-epoxide (DE-2) with HCl, which yields only trans-chlorohydrin 8. The hydrolysis of cis-chlorohydrin 9 in 10:90 dioxane-water solutions yields the same ratio of tetrols ( approximately 89% cis/11% trans) as that formed by acid-catalyzed hydrolysis of DE-1. This result again contrasts with the hydrolysis of trans-chlorohydrin 8, which undergoes hydrolysis to give tetrols in a ratio different from that from acid-catalyzed hydrolysis of DE-2. A marked common ion rate depression in the hydrolysis of cis-chlorohydrin 9 is observed, which shows that hydrolysis proceeds via an intermediate carbocation that has a sufficient lifetime to be trapped by external chloride ion. The observation that DE-1 reacts with HCl to give mainly the cis-chlorohydrin is rationalized by quantum chemical calculations that suggest that the cis-chlorohydrin is more stable than the epimeric trans-chlorohydrin.     

Cellulose/chitosan hybrid nanofibers from electrospinning of their ester derivatives

A facile approach has been established to generate cellulose/chitosan hybrid nanofibers with full range of compositions by electrospinning of their ester derivatives, cellulose acetate (CA) and dibutyryl chitin (DBC), followed by alkaline hydrolysis to cellulose (Cell) and chitosan (CS). DBC was synthesized by acid-catalyzed acylation of chitin (CHI) with butyric anhydride and the newly formed butyl groups on C3 and C6 were confirmed by FT-IR and ¹HNMR. DBC had robust solubility in acetone, DMAc, DMF, ethanol, and acetic acid, all except ethanol were also solvents for CA, allowing mixing of these ester derivatives. Fiber formation by electrospinning of either DBC or CA alone and together in these common solvents and their mixtures were studied. The 1/1 acetone/acetic acid was found to be the optimal solvent system to generate fibers from either DBC or CA as well as their mixtures at all CA/DBC ratios, resulting in hybrid fibers with diameters ranging from 30 to 350 nm. DBC and CA were well mixed and showed no phase separate in the hybrid fibers. Alkaline hydrolysis (NaOH) of the equal mass CA/DBC nanofibers regenerated Cell and CHI readily via O-deacylation, then proceeded to further deacetylate CHI to CS via N-deacetylation at higher alkaline concentrations and/or temperatures. Under conditions studied, hydrolysis with 5N NaOH at 100 °C for 3 h was optimal to regenerate cellulose/chitosan hybrid nanofibers.     

Isocratic separations of closely-related mono- and disaccharides by high-performance anion-exchange chromatography with pulsed amperometric detection using dilute alkaline spiked with barium acetate.

Mixtures of closely related mono- and disaccharides may be efficiently separated by high-performance anion-exchange chromatography (HPAEC) only when relatively dilute alkaline eluents are employed (i.e., < 20 mM NaOH). The main drawbacks of these eluent solutions are (i) column regeneration between runs, (ii) poor reproducibility of the retention times, and (iii) the need for post-column base addition for enhancing sensitivity. Here, we describe some examples of isocratic separations of carbohydrates by HPAEC coupled with pulsed amperometric detection (PAD) accomplished by carbonate-free alkaline eluents (i.e., 5-20 mM NaOH) obtained upon addition of Ba(OAc)2 (1-2 mM). These separations include aldohexoses (i.e., galactose, glucose, and mannose), aminohexoses (i.e., glucosamine and galactosamine) and their N-acylated derivatives (i.e., N-acetylglucosamine and N-acetylgalactosamine) along with some isomeric disaccharides (i.e., lactose, lactulose and epilactose). The separation of closely related isomers of trehalose, alpha,alpha, alpha,beta, and beta,beta, is also presented. It is recommended to add Ba(OAc)2 to NaOH solutions several hours before using the alkaline eluent (i.e., 12-24 h) to ensure complete barium carbonate precipitation in the eluent reservoir. Adopting such a simple strategy can be especially useful for performing carbohydrate separations under isocratic conditions in which no regeneration and or re-equilibration of column between runs is required. Excellent repeatability of retention data throughout a three-day working session was observed, with relative standard deviations ranging from 2.0 to 3.7%, and from 0.5 to 2.0%, as day-to-day and within-day values, respectively. In addition, there was no need for postcolumn addition of strong bases to the eluent, and successful applications of the present approach confirmed its validity and practicability with detection limits of simple carbohydrates in the picomole range.     

Notizen zur Synthese sulfonierter Derivate von 5,6,7,8-Tetrahydro-1-naphthylamin und 5,6,7,8-Tetrahydro-2-naphthylamin

Notes on the Synthesis of Sulfonated Derivatives of 5,6,7,8-Tetrahydro-1-naphthylamine and 5,6,7,8-Tetrahydro-2-naphthylamine Sulfonation of 5,6,7,8-tetrahydro-1-naphthylamine ( 1 ) with sulfuric acid gave a mixture of 1-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 2 ), 4-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 13 ) and 4-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 3 ). The same reaction with 5,6,7,8-tetrahydro-2-naphthylamine ( 20 ) yielded 3-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 21 ); formation of 2-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 16 ) or of 3-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 24 ) was not observed. Treatment of 4-bromo-5,6,7,8-tetrahydro-1-naphthylamine ( 4 ) or of its 4-chloro analogue 5 with amidosulfuric acid gave 1-amino-4-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 9 ) and its 4-chloro analogue 10 , respectively, which were dehalogenated to 2 . Preparations of 13 and 24 were achieved by sulfonation of 5-nitro-1,2,3,4-tetrahydronaphthalene ( 14 ) and 6-nitro-1,2,3,4-tetrahydronaphthalene ( 22 ) to 4-nitro-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 15 ) and 3-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 23 ), respectively, followed by Béchamp reductions. The sulfonic acid 13 was also obtained by hydrogenolysis of 4-amino-1-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 11 ) or of its 1-chloro analogue 12 ; compounds 11 and 12 were synthesized from N-(4-bromo-5,6,7,8-tetrahydro-1-naphthyl)acetamide ( 7 ) and from its 4-chloro analogue 8 , respectively, by sulfonation with oleum and subsequent hydrolysis. By ‘baking’ the hydrogensulfate salt of 1 or 20 compounds 3 and 21 were obtained, respectively. Synthesis of 16 was achieved by sulfur dioxide treatment of the diazonium chloride derived from 2-nitro-5,6,7,8-tetrahydro-1-naphthylamine ( 17 ) giving 2-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonyl chloride ( 18 ), followed by hydrolysis of 18 to the corresponding sulfonic acid 19 and final reduction.     

Cholinesterase inhibiting withanolides from Withania somnifera

A total of two new (1, 2) and four known (3-6) withanolides were isolated from the whole plant of Withania somnifera. Their structures were elucidated on the basis of spectroscopic techniques and were characterized as 6alpha,7alpha-epoxy-3beta,5alpha,20beta-trihydroxy-1-oxowitha-24-enolide (1), 5beta,6beta-epoxy-4beta,17alpha,27-trihydroxy-1-oxowitha-2,24-dienolide (2), withaferin-A (3), 2,3-dihydrowithaferin-A (4), 6alpha,7alpha-epoxy-5alpha,20beta-dihydroxy-1-oxowitha-2,24-dienolide (5), and 5beta,6beta-epoxy-4beta-hydroxy-1-oxowitha-2,14,24-trienolide (6), respectively. Compounds 2, 3, 5, and 6 displayed inhibitory potential against butyrylcholinesterase, but only compounds 3, 4, and 6 were found to be active against acetylcholinesterase.     

Zur Synthese sulfonierter Derivate von 2-Fluoranilin

Syntheses of Sulfonated Derivatives of 2-Fluoroaniline Synthesis of 4-amino-3-fluorobenzenesulfonic acid ( 3 ) was achieved in two ways: reaction of 2-fluoroaniline ( 1 ) with amidosulfonic acid and by first conventionally converting 4-nitro-3-fluoroaniline ( 8 ) to 4-nitro-3-fluorobenzenesulfonyl chloride ( 9 ) followed subsequently by hydrolysis to 3-fluoro-4-nitrobenzenesulfonic acid ( 10 ) and reduction. Hydrogenolysis of 3 gave sulfanilic acid ( 7 ). Both, sulfonation of fluorobenzene ( 6 ) to 4-fluorobenzenesulfonic acid ( 11 ) followed by nitration and sulfonation of 1-fluoro-2-nitrobenzene ( 12 ) led to 4-fluoro-3-nitrobenzenesulfonic acid ( 13 ). Reduction of 13 gave the isomeric 3-amino-4-fluorobenzenesulfonic acid ( 4 ), which was also obtained both by sulfonation of 1 and by sulfonation of o-fluoroacetanilide ( 14 ) followed by hydrolysis. Selective hydrogenolyses of 2-amino-5-bromo-3-fluorobenzenesulfonic acid ( 15 ), prepared by reaction of 4-bromo-2-fluoroaniline ( 16 ) with amidosulfonic acid, and of 4-amino-2-bromo-5-fluorobenzenesulfonic acid ( 20 ), obtained by sulfonation of 5-bromo-2-fluoroaniline ( 19 ) yielded the isomers 2-amino-3-fluorobenzenesulfonic acid ( 5 ) and 3 , respectively. The fourth isomer, 3-amino-2-fluorobenzenesulfonic acid ( 2 ), was synthesized by sulfur dioxide treatment of the diazonium chloride derived from 2-fluoro-3-nitroaniline ( 21 ) to 2-fluoro-3-nitrobenzenesulfonyl chloride ( 22 ), followed by hydrolysis to 2-fluoro-3-nitrobenzenesulfonic acid ( 23 ) and final Béchamp-reduction.     

Mechanistic study of protein phosphatase-1 (PP1), a catalytically promiscuous enzyme

The reaction catalyzed by the protein phosphatase-1 (PP1) has been examined by linear free energy relationships and kinetic isotope effects. With the substrate 4-nitrophenyl phosphate (4NPP), the reaction exhibits a bell-shaped pH-rate profile for kcat/KM indicative of catalysis by both acidic and basic residues, with kinetic pKa values of 6.0 and 7.2. The enzymatic hydrolysis of a series of aryl monoester substrates yields a Br?nsted beta(lg) of -0.32, considerably less negative than that of the uncatalyzed hydrolysis of monoester dianions (-1.23). Kinetic isotope effects in the leaving group with the substrate 4NPP are (18)(V/K) bridge = 1.0170 and (15)(V/K) = 1.0010, which, compared against other enzymatic KIEs with and without general acid catalysis, are consistent with a loose transition state with partial neutralization of the leaving group. PP1 also efficiently catalyzes the hydrolysis of 4-nitrophenyl methylphosphonate (4NPMP). The enzymatic hydrolysis of a series of aryl methylphosphonate substrates yields a Br?nsted beta(lg) of -0.30, smaller than the alkaline hydrolysis (-0.69) and similar to the beta(lg) measured for monoester substrates, indicative of similar transition states. The KIEs and the beta(lg) data point to a transition state for the alkaline hydrolysis of 4NPMP that is similar to that of diesters with the same leaving group. For the enzymatic reaction of 4NPMP, the KIEs are indicative of a transition state that is somewhat looser than the alkaline hydrolysis reaction and similar to the PP1-catalyzed monoester reaction. The data cumulatively point to enzymatic transition states for aryl phosphate monoester and aryl methylphosphonate hydrolysis reactions that are much more similar to one another than the nonenzymatic hydrolysis reactions of the two substrates.     

Studies with polyfunctionally substituted heteroaromatics: A facile route for the synthesis of polyfunctionally substituted N-aminopyridines, 1,2,4-triazolo[1,5-a]pyridines and isoquinolines

The reactions of formaldehyde and acetaldehyde with active methylene compounds, followed by reaction with cyanoacetic acid hydrazide 2, afforded N-aminopyridine-2-one derivatives 5a-f. In contrast, the reactions of cyanoacetic acid hydrazide 2 with aliphatic aldehydes and cyanothioacetamide afforded pyridinethione derivatives 11a-b. Also, the reactions of active methylene compounds with formaldehyde and cyanoacetamide afforded pyridin(1H)-2-one derivatives 12a-c. The reactions of 5b with aldehydes and ketones afforded compounds 13a, b, 14, and 15, respectively. The reactions of 5b with arylidinemalononitriles 16a,b afforded isoquinoline derivatives 19a,b. Compound 19b by hydrolysis gave the final product 20. Compound 20 could also be formed by hydrolysis of 5b to give 21, followed by the reaction with 16b. © 1997 John Wiley & Sons, Inc.     

Peculiarities of the preparation of copolymers of acrylamide with sodium acrylate in inverse emulsions

The polymerization of acrylamide (AA) in inverse emulsions in the presence of saponifying agents (NaOH and Na₂CO₃) and potassium persulphate at 30–50° has been investigated. The rates of the polymerization and alkaline hydrolysis increase with increasing concentration of saponifying agents, AA, initiator and temperature. The molecular weight of copolymers decreases with increasing concentration of saponifying agents for polymerization in water-toluene emulsions and in aqueous solutions. It has been shown that the alkaline hydrolysis in inverse emulsions polymerization of AA is a second-order reaction, with rate proportional to both the amide and the alkaline agent concentrations. The effective overall energies of activation of the alkaline hydrolysis were 57.5 (in the presence of NaOH) and 57.0 kJ/mol (in the presence of Na₂CO₃).     

Non-steroidal antiinflammatory agents. VI. Synthesis of 10-oxo-5H-pyrrolo[1,2-b]isoquinoline-3-acetic Acid,a conformationally restricted analogue of tolmetin

The synthesis of 10-oxo-5H-pyrrolo[1,2-b]isoquinoline-3-acetic acid 4 , a tricyclic analogue of tolmetin which might show significant analgesic-antiinflammatory activity, has been accomplished in four steps. Alkylation of ethyl 2-pyrrolylglyoxylate ( 15 ) with 2-cyanobenzyl bromide afforded derivative 16 , which was transformed by the Huang-Minion reaction into the dicarboxylic acid 6 . Cyclization of this key intermediate to 17 , followed by alkaline hydrolysis, afforded 10-oxo-5H-pyrrolo[1,2–6]isoquinoline-3-acetic acid ( 4 ). Various attempted syntheses of 6 are also discussed.