4‐Chloro‐3′‐methylsulfinyl‐5(6 or 8)‐nitro‐3,4′‐diquinolinyl sulfides

Reaction of 4‐chloro‐3′‐methylthio‐3,4′‐diquinolinyl sulfides 3, 9b, 9c with a nitrating mixture proceeds via the 3′‐methylthio group monooxidation and yields 3′‐methylsulfinyl diquinolinyl sulfides 4, 5b, 5c , respectively. Further treatment of 4 with a nitrating mixture followed as C₅‐ and C₈‐nitration and gives mixture of 5a and 5c. Treatment of 3′‐methylsulfinyl quinolines 6 and 7 with hydrochloric acid/potassium iodide system causes reduction of the sulfoxide group in 6 and 7 to the sulfide group yielding 8 , in case of 4‐methoxyquinolines 6 , hydrolysis of the 4‐methoxyquinoline moiety to the 4‐quinolinone moiety takes place simultaneously. The proton and carbon chemical shifts of 4 and 5a were completely assigned following COSY, HETCOR and INEPT or COLOC studies.     

New P‐ligands: 3‐(ethyl‐phenylphosphinato‐) 1,2,3,6‐tetrahydro‐ and 1,2,3,4,5,6‐hexahydrophosphinine derivatives

The trimethylaluminum‐mediated Michael addition of ethyl phenyl‐H‐phosphinate to 1,2‐dihydrophosphinine oxides ( 1A ) yielded 3‐(EtOPhP(O))‐1,2,3,6‐tetrahydrophosphinine oxides ( 4 ) in a selective manner, as a mixture of only two diastereomers. In the above type of reactions (e.g., in that of 1Aa and Ph₂P(O)H), Me₃Al could not be substituted by microwave irradiation due to low efficiency. Catalytic hydrogenation of the Michael adducts ( 4 ) led to 3‐(EtOPhP(O)‐1,2,3,4,5,6‐hexahydrophosphinine oxides 5 , in the case of P‐phenyl substituent ( 5a ), as a mixture of only two diastereomers, while in the instance of the P‐ethoxy derivative ( 5b ), as a mixture of four isomers. Stereostructure of the products ( 5 ) was substantiated on the basis of analogies and stereospecific NMR couplings. The predominant conformations of compounds 4a , 4b , 5a , and 5b‐1 were determined by HF/6‐31G* calculations. Reduction of P(1)–Ph heterocycles 4a and 5a by phenylsilane resulted in monodeoxygenation to afford P‐ligands 6 and 8 , respectively, that were protected as the corresponding phosphine boranes ( 7 and 9 , respectively). © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:747–753, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20365     

Regioselective synthesis of pentacyclic polyheterocycles: Sequential [3,3] sigmatropic rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐1‐phenyl‐1,8‐naphthyridin‐2(1H)‐ones

A number of 4‐aryloxymethyl‐6‐phenyl‐2H‐pyrano[3,2‐c][1,8]naphthyridin‐5(6H)‐ones ( 4a‐f ) are regioselectively synthesized in 72‐78% yield by the Claisen rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐1‐phenyl‐1,8‐naphthyridin‐2(1H)‐ones ( 3a‐f ) in refluxing chlorobenzene for 4‐6 h. These products are then subjected to a second Claisen rearrangement catalyzed by anhydrous AlCl₃ at room temperature for 2 h to give hitherto unreported pentacyclic heterocycles ( 5a‐f ) in 78‐85% yield.     

Synthesis of 1‐Methyl‐6,10‐diphenylheptalene Derivatives

The reduction of heptalene diester 1 with diisobutylaluminium hydride (DIBAH) in THF gave a mixture of heptalene‐1,2‐dimethanol 2a and its double‐bond‐shift (DBS) isomer 2b (Scheme 3). Both products can be isolated by column chromatography on silica gel. The subsequent chlorination of 2a or 2b with PCl₅ in CH₂Cl₂ led to a mixture of 1,2‐bis(chloromethyl)heptalene 3a and its DBS isomer 3b . After a prolonged chromatographic separation, both products 3a and 3b were obtained in pure form. They crystallized smoothly from hexane/Et₂O 7 : 1 at low temperature, and their structures were determined by X‐ray crystal‐structure analysis (Figs. 1 and 2). The nucleophilic exchange of the Cl substituents of 3a or 3b by diphenylphosphino groups was easily achieved with excess of (diphenylphospino)lithium (=lithium diphenylphosphanide) in THF at 0° (Scheme 4). However, the purification of 4a / 4b was very difficult since these bis‐phosphines decomposed on column chromatography on silica gel and were converted mostly by oxidation by air to bis(phosphine oxides) 5a and 5b . Both 5a and 5b were also obtained in pure form by reaction of 3a or 3b with (diphenylphosphinyl)lithium (=lithium oxidodiphenylphospanide) in THF, followed by column chromatography on silica gel with Et₂O. Carboxaldehydes 7a and 7b were synthesized by a disproportionation reaction of the dimethanol mixture 2a / 2b with catalytic amounts of TsOH. The subsequent decarbonylation of both carboxaldehydes with tris(triphenylphosphine)rhodium(1+) chloride yielded heptalene 8 in a quantitative yield. The reaction of a thermal‐equilibrium mixture 3a / 3b with the borane adduct of (diphenylphosphino)lithium in THF at 0° gave 6a and 6b in yields of 5 and 15%, respectively (Scheme 4). However, heating 6a or 6b in the presence of 1,4‐diazabicyclo[2.2.2]octane (DABCO) in toluene, generated both bis‐phosphine 4a and its DBS isomer 4b which could not be separated. The attempt at a conversion of 3a or 3b into bis‐phosphines 4a or 4b by treatment with t‐BuLi and Ph₂PCl also failed completely. Thus, we returned to investigate the antipodes of the dimethanols 2a, 2b , and of 8 that can be separated on an HPLC Chiralcel‐OD column. The CD spectra of optically pure (M)‐ and (P)‐configurated heptalenes 2a, 2b , and 8 were measured (Figs. 4, 5, and 9).     

Thiiranation of 2′‐adamantylidene‐9‐benzonorbornenylidene using 4,4′‐oligothiodimorpholine and brønsted acid

On leaving 4,4′‐dithiodimorpholine 6 powder undisturbed at room temperature over 10 years, it led to the formation of 4,4′‐tetrathiodimorpholine 7 . Reactions of 2′‐adamantylidene‐9‐benzonorbornenyidene 1 with 6, 7 , and 4,4′‐thiodimorpholine 8 and a Brønsted acid in CH₂Cl₂ at room temperature proceeded to afford the corresponding thiiranes, 2 and 3 . The order of reactivity of 4,4′‐oligothiodimorpholines combined with a Brønsted acid is 7 > 6 > 8 . The thiirane 3 was transformed to 1 and 2 under the reaction conditions. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:12–18, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20505     

Synthesis and antitumor activity of novel 1‐(2′‐alkyl(or phenyl)thioethoxy)methyl‐5‐fluorouracils and their oxidation products

A series of novel 1‐(2′‐alkyl(or phenyl)thioethoxy)methyl‐5‐fluorouracils ( 6 ) were synthesized in three steps from 5‐fluorouracil. They were oxidized into sulfoxide ( 7 ) and sulfone ( 8 ) derivatives by NaIO₄ and H₂O₂ 30%/DEAD (diethyl azodicarboxylate), respectively, in high yields. In order to obtain structural information, sulfoxide 7g was characterized by X‐ray diffraction analysis. The preliminary bioassay indicated that the compounds 6a and 7g exhibit potential antitumor activity. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:543–548, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20059     

The pummerer and the thio-claisen–type rearrangements of naphtho[1,8-bc]-1,5-dithiocin monooxide and N-p-tosylsulfilimine

Naphtho[1,8-bc]-1,5-dithiocin N-p-tosylsulfilimine ( 8 ) and monosulfoxide ( 9 ) were prepared. On treatment with conc. H₂SO₄, both the sulfilimine ( 8 ) and sulfoxide ( 9 ) gave the dithia dication which was converted to the sulfoxide by hydrolysis. The H–D exchange reaction of ( 8 ) took place highly regioselectively to afford the monodeuterated ( 8–D ) at the a-position of the N-tosyl group. The Pummerer rearrangement reaction of monooxide ( 9 ) with acetic anhydride gave the a-acetoxy derivative by the dication ( 10b ), while a new thio-Claisen rearrangement of sulfilimine ( 8 ) t-BuOK in CH₂Cl₂ gave 2-allyl-naphtho[1,8-bc]-1,5-dithiole. © John Wiley & Sons, Inc.     

A Novel Synthesis of 1‐Aryl‐6‐bromo‐3‐(5‐ethylthio‐4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐pyrazolo[4,3‐b]quinolin‐9(4H)‐ones via Thermal Cyclization of 4‐Azidopyrazoles

2‐Aryl‐hydrazononitriles 3a , 3b , 3c were prepared by coupling 3‐ethylthio‐5‐cyanomethyl‐4‐phenyl‐1,2,4‐triazole ( 1 ) with diazonium salts 2a , 2b , 2c . Reacting 3a , 3b , 3c with both ethyl bromoacetate ( 4a ) and 4‐bromobenzyl bromide ( 4b ) in DMF, in the presence of K₂CO₃, at 80 °C for 3–4 h, gave the corresponding 4‐amino‐pyrazoles 6a , 6b , 6c , 6d , 6e , 6f . Diazotization of 6a , 6b , 6c , 6d , 6e , 6f , followed by reaction with NaN₃, leads to the formation of 4‐azidopyrazoles 8a , 8b , 8c , 8d , 8e , 8f , a new heterocyclic ring system. Interestingly, fusion of 4‐azidopyrazoles 8d , 8e , 8f at temperature higher than their melting points with 5 °C for 2 min did not give the expected fused pyrazolo[4,3‐c]isoxazoles 9 but furnished instead the novel pyrazolo[4,3‐b]quinolinones 10a , 10b , 10c , in high yields.     

Synthesis and tuberculostatic activity of novel N′‐methyl‐4‐(pyrrolidin‐1‐yl)picolinohydrazide and N′‐methylpyrimidine‐2‐carbohydrazide derivatives

The synthesis of N′‐methyl‐4‐(pyrrolidin‐1‐yl)picolinohydrazide and N′‐methyl‐pyrimidine‐2‐carbohydrazide derivatives ( 5a and 5b ) was carried out. These compounds were used as starting materials to obtain methyl N′‐methylhydrazinecarbodithioates 6a and 6b , which, on reaction with either triethylamine or hydrazine, gave corresponding 1,3,4‐oxadiazioles 7a and 7b or 1,2,4‐triazoles 9a and 9b with the free NH₂ group at the N‐4 position, respectively. Compounds 8a – e , particularly containing cyclic amines at N‐4 of the 1,2,4‐triazole ring, were also obtained. Synthesized compounds were tested in vitro for their activity against Mycobacterium tuberculosis. The structure–activity relationship analysis for obtained compounds was done. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:223–230, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21008     

Oxidation polymerization of a charge‐transfer complex of 2,6‐bis(2‐thienyl)‐1,4‐dithiafulvene with 7,7,8,8‐tetracyanoquinodimethane

A π‐conjugated poly(α‐dithienylen‐dithiafulvene) ( 2 ) was obtained by the oxidation polymerization of 2,6‐bis(2‐thienyl)‐1,4‐dithiafulvene ( 1 ) as a dithiafulvene monomer derived from 4‐(2‐thienyl)‐1,2,3‐thiadiazole. When a solution of 1 in CHCl₃ was added to a stirred solution of FeCl₃ in CHCl₃, only the low‐molecular‐weight product 2 was obtained. The mixture was stirred for 15 h with an N₂ flow. The polymerization at higher temperatures resulted in polymers with large insoluble fractions. A higher molecular weight polymer was obtained by the oxidation polymerization of a charge‐transfer complex of 1 with 7,7,8,8‐tetracyanoquinodimethane (compound 3 ). In contrast to 2 , polymer 4 was readily soluble in dimethyl sulfoxide, dimethylformamide, and acetone and partially soluble in tetrahydrofuran and methanol and had a larger molecular weight (peak top molecular weight = 37,000). The conductivity of polymer 4 was 3 orders of magnitude larger than that of polymer 2 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6592–6598, 2005     

Quinolone analogs 11: Synthesis of novel 4‐quinolone‐3‐carbohydrazide derivatives with antimalarial activity

The reaction of the 6‐substituted 1‐methyl‐4‐quinolone‐3‐carboxylates 10a , 10b with hydrazine hydrate gave the 3‐carbohydrazides 7a , 7b , respectively, whose reaction with 2‐, 3‐, and 4‐pyridinecarbaldehydes afforded the 3‐(N²‐pyridylmethylene)carbohydrazides 8a , 8b , 8c and 9a , 9b , 9c . The Curtius rearrangement of compound 7b provided the N,N′‐bis(4‐quinolon‐3‐yl)urea 14 presumably via the 3‐carboazide 11 and then 3‐isocyanate 12 . Compounds 7a , 8a , and 9a were found to possess antimalarial activity from the in vitro screening data. J. Heterocyclic Chem.,(2011).     

A Stereospecific `2‐Aza‐divinylcyclopropane' Rearrangement

The stereochemical course of the thermal 2‐aza‐Cope rearrangement of the optically pure acyl azide (−)‐(1S)‐ 5 was investigated by determination of the absolute configuration of the rearrangement product (1R,8S)‐ 9 . The reaction proceeds by a sequence of stereospecific steps from 5 to an equilibrating mixture of exo‐ and endo‐isocyanates 6 and 7 . The endo‐isomer 7 undergoes Cope rearrangement to the putative intermediate 8 , which is trapped and characterized as the adduct 9b of butan‐1‐ol. The absolute configuration of 9b was determined by its reduction to the amide 20 , and determination of the X‐ray structure of the N‐camphanoylamide 21 derived from camphanic acid of known absolute configuration.     

Preparation of 2‐phenyl‐2‐hydroxymethyl‐4‐oxo‐1,2,3,4‐tetrahydroquinazoline and 2‐methyl‐4‐oxo‐3,4‐dihydroquinazoline derivatives formation

The cyclization of phenacyl anthranilate has been studied with the aim to develop the synthesis of 2‐(2′‐aminophenyl)‐4‐phenyloxazole. However, a different course of the reaction than expected was observed. 2‐Phenyl‐2‐hydroxymethyl‐4‐oxo‐1,2,3,4‐tetrahydroquinazoline ( 3a ) was formed by the reaction of phenacyl anthranilate ( 2 ) with ammonium acetate under various conditions. 3‐Hydroxy‐2‐phenyl‐4(1H)‐quinolinone ( 4 ) arose by heating compound 3a in acetic acid. The same compound was obtained by melting compound 3a , but the yield was lower. Different types of products resulted in the reaction of compound 3a with acetic anhydride. Under mild conditions acetylated products 2‐acetoxymethyl‐2‐phenyl‐4‐oxo‐1,2,3,4‐tetrahydroquinazoline ( 7a ) and 2‐acetoxymethyl‐3‐acetyl‐2‐phenyl‐4‐oxo‐1,2,3,4‐tetrahydroquinazoline ( 8 ) were prepared. If the reaction was carried out under reflux of the reaction mixture, molecular rearrangement took place to give cis and trans 2‐methyl‐4‐oxo‐3‐(1‐phenyl‐2‐acetoxy)vinyl‐3,4‐dihydroquinazolines ( 9a and 9b ). All prepared compounds have been characterised by their ¹H, ¹³C and ¹⁵N NMR spectra, IR spectra and MS.     

Formation of 6‐Methyl‐7,11‐diphenylheptaleno[1,2‐c]furanones

The dehydrogenation reaction of a mixture of heptalene‐1,2‐ and heptalene‐4,5‐dimethanols 4a and 4b with basic MnO₂ in AcOEt at room temperature led to the formation of the corresponding heptaleno[1,2‐c]furan‐1‐one 6a and heptaleno[1,2‐c]furan‐3‐one 7a (Scheme 2). Both products can be isolated by chromatography on silica gel. The methylenation of the furan‐3‐one 7a with 1 mol‐equiv. of Tebbe's reagent at ?25 to ?30° afforded the 2‐isopropenyl‐5‐methylheptalene‐1‐methanol 9a , instead of the expected 3,6‐dimethylheptaleno[1,2‐c]furan 8 (Scheme 3). Also, the treatment of 7a with Takai's reagent did not lead to the formation of 8 . On standing in solution at room temperature, or more rapidly on heating at 60°, heptalene 9a undergoes a reversible double‐bond shift (DBS) to 9b with an equilibrium ratio of 1 : 1.     

Synthesis of 1‐silacyclopent‐2‐ene derivatives using 1,2‐hydroboration, 1,1‐organoboration and protodeborylation

The reaction of di(alkyn‐1‐yl)vinylsilanes R¹(H₂C═CH)Si(C≡C―R)₂ (R¹ = Me ( 1 ), Ph ( 2 ); R = Bu (a), Ph (b), Me₂HSi (c)) at 25°C with 1 equiv. of 9‐borabicyclo[3.3.1]nonane (9‐BBN) affords 1‐silacyclopent‐2‐ene derivatives ( 3a , 3b , 3c , 4a , 4b ), bearing one Si―C≡C―R function readily available for further transformations. These compounds are formed by consecutive 1,2‐hydroboration followed by intramolecular 1,1‐carboboration. Treated with a further equivalent of 9‐BBN in benzene they are converted at relatively high temperature (80–100°C) into 1‐alkenyl‐1‐silacyclopent‐2‐ene derivatives ( 5a , 5b 6a , 6b ) as a result of 1,2‐hydroboration of the Si―C≡C―R function. Protodeborylation of the 9‐BBN‐substituted 1‐silacyclopent‐2‐ene derivatives 3 , 4 , 5 , 6 , using acetic acid in excess, proceeds smoothly to give the novel 1‐silacyclopent‐2‐ene ( 7 , 8 , 9 , 10 ). The solution‐state structural assignment of all new compounds, i.e. di(alkyn‐1‐yl)vinylsilanes and 1‐silacyclopent‐2‐ene derivatives, was carried out using multinuclear magnetic resonance techniques (¹H, ¹³C, ¹¹B, ²⁹Si NMR). The gas phase structures of some examples were calculated and optimized by density functional theory methods (B3LYP/6‐311+G/(d,p) level of theory), and ²⁹Si NMR parameters were calculated (chemical shifts δ²⁹Si and coupling constants ⁿJ(²⁹Si,¹³C)). Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and some reactions of 4‐(ethoxycarbonyl)‐1,5‐diphenyl‐1H‐pyrazole‐3‐carboxylic acid

1,5‐Diphenyl‐1H‐pyrazole‐3,4‐dicarboxylic acid‐4‐ethyl ester 2 , obtained from the 4‐ethoxycarbonyl‐5‐phenyl‐2,3‐furandione 1 and N‐benzylidene‐N′‐phenyl hydrazine, was converted via reactions of its acid chloride 3 with various alcohols or N‐nucleophiles into the corresponding ester 5 or amide derivatives 6 , respectively. In addition, 2 was decarboxylated to give ethyl 1,5‐diphenylpyrazole‐4‐carboxylate 4 . Nitrile 7 derivative of 2 was also obtained by dehydration of 6a in a mixture of SOCl₂ and DMF. While cyclocondensation reaction of 2 with hydrazine hydrate leads to the formation of pyrazolo[3,4‐d]pyridazine‐4,7‐dione 8 , the reaction of 3 with anhydrous hydrazine provided a new bis pyrazole derivative 9 .     

Intriguing Influence of the Solvent on the Regioselectivity of Sulfoxide Thermolysis in β‐Amino‐α‐sulfinyl Esters

The sulfoxide thermolysis of the diastereoisomeric methyl (3R,4aS,10aR)‐6‐methoxy‐1‐methyl‐3‐(phenylsulfinyl)‐1,2,3,4,4a,5,10,10a‐octahydrobenzo[g]quinoline‐3‐carboxylates 3a and 3′b in toluene yields, by loss of benzenesulfenic acid, an almost 1 : 1 mixture of the vinylogous urethane 2b and the isomeric α‐aminomethyl enoate 2a . When this elimination is performed in acetic acid, the enoate 2a is formed rather selectively. The same solvent effects on the regioselectivity of the elimination of benzenesulfenic acid are observed with a simple sulfoxide of ethyl piperidine‐3‐carboxylate ( 7 ).     

Aminoethynyl‐silanes, ‐germanes and ‐stannanes: novel organometallic‐substituted enamines via 1,1‐organoboration

The reactions of diethylaminoethynyl(trimethyl)silane (1), bis(diethylaminoethynyl)methylsilane (2), diethylaminoethynyl(trimethyl)germane (3), dimethylaminoethynyl(triethyl)germane (4), diethylaminoethynyl(trimethyl)stannane (5) and methyl(phenyl)aminoethynyl(trimethyl)stannane (6) with trialkylboranes [BEt₃ (7b), BPr₃ (7c), BⁱPr₃ (7d) and 9‐alkyl‐9‐borabicyclo[3.3.1]nonanes 9‐Me‐9‐BBN (8a) and 9‐Et‐9‐BBN (8b)] were studied. The alkynes 1 and 2 did not react even with boiling BEt₃, whereas the reactions of 3–6 afforded mainly novel enamines [(E)‐1‐amino‐1‐trialkylgermyl‐2‐dialkylboryl‐alkenes (9, 10), (E)‐1‐diethylamino‐1‐trimethylstannyl‐2‐dialkylboryl‐alkenes (11, 12), (E)‐1‐methyl(phenyl)amino‐1‐trimethylstannyl‐2‐dialkylboryl‐alkenes (13, 14)]. This particular stereochemistry is unusual for products from 1,1‐organoboration reactions, indicating a special influence of the amino group. The starting materials and products were characterized by multinuclear magnetic resonance spectroscopy (¹H, ¹¹B, ¹³C, ¹⁵N, ²⁹Si, ¹¹⁹Sn NMR). Copyright © 2003 John Wiley & Sons, Ltd.     

7‐Halogenated 7‐Deazapurine 2′‐Deoxyribonucleosides Related to 2′‐Deoxyadenosine, 2′‐Deoxyxanthosine,and 2′‐Deoxyisoguanosine: Syntheses and Properties

A series of 7‐fluorinated 7‐deazapurine 2′‐deoxyribonucleosides related to 2′‐deoxyadenosine, 2′‐deoxyxanthosine, and 2′‐deoxyisoguanosine as well as intermediates 4b – 7b, 8, 9b, 10b , and 17b were synthesized. The 7‐fluoro substituent was introduced in 2,6‐dichloro‐7‐deaza‐9H‐purine ( 11a ) with Selectfluor (Scheme 1). Apart from 2,6‐dichloro‐7‐fluoro‐7‐deaza‐9H‐purine ( 11b ), the 7‐chloro compound 11c was formed as by‐product. The mixture 11b / 11c was used for the glycosylation reaction; the separation of the 7‐fluoro from the 7‐chloro compound was performed on the level of the unprotected nucleosides. Other halogen substituents were introduced with N‐halogenosuccinimides ( 11a → 11c – 11e ). Nucleobase‐anion glycosylation afforded the nucleoside intermediates 13a – 13e (Scheme 2). The 7‐fluoro‐ and the 7‐chloro‐7‐deaza‐2′‐deoxyxanthosines, 5b and 5c , respectively, were obtained from the corresponding MeO compounds 17b and 17c , or 18 (Scheme 6). The 2′‐deoxyisoguanosine derivative 4b was prepared from 2‐chloro‐7‐fluoro‐7‐deaza‐2′‐deoxyadenosine 6b via a photochemically induced nucleophilic displacement reaction (Scheme 5). The pK_a values of the halogenated nucleosides were determined (Table 3). ¹³C‐NMR Chemical‐shift dependencies of C(7), C(5), and C(8) were related to the electronegativity of the 7‐halogen substituents (Fig. 3). In aqueous solution, 7‐halogenated 2′‐deoxyribonucleosides show an approximately 70% S population (Fig. 2 and Table 1).     

Synthesis and antimicrobial activity of new benzofuranyl‐1,3‐benzoxazines and 1,3‐benzoxazin‐2‐ones

New benzofuranyl‐1,3‐benzoxazines and 1,3‐benzoxazin‐2‐ones are synthesized in which benzofuran is coupled with 1,3‐benzoxazines and 1,3‐benzoxazin‐2‐ones through ‐CONH‐ and ‐COCH₂‐ bridges, respectively. The antimicrobial activity of these compounds is reported.