Showing papers on "Pyran published in 1995"

Photochromic naphthopyran compounds

Abstract: Described are novel reversible photochromic naphthopyran compounds, examples of which are compounds substituted at the 3 position of the pyran ring with (i) an aryl substituent and (ii) a phenyl substituent having a 5- or 6-member heterocyclic ring fused at the number 3 and 4 carbon atoms of the phenyl substituent. Also described are organic host materials that contain or that are coated with such compounds. Articles such as ophthalmic lenses or other plastic transparencies that incorporate the novel naphthopyran compounds or combinations thereof with complementary photochromic compounds, e.g., spiro(indoline) type compounds, are also described.

Process for trans-6-[2-(substituted-pyrrol-1-yl)alkyl]pyran-2-one inhibitors of cholesterol synthesis

Abstract: An improved process for the preparation of trans-6-[2-(substituted-pyrrole-1-yl)alkyl]pyran-2-ones by a novel synthesis is described where α-metalated N,N-disubstituted acetamide is converted in seven operations to the desired products, and specifically, a process for preparing (2R-trans)-5-(4-fluorophenyl)-2-(1-methylethyl)-N,4-diphenyl-1-[2-(tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl)ethyl]-1H-pyrrole-3-carboxamide, as well as other valuable intermediates used in the processes and prodrugs which are bioconverted to hypolipidemic and hypocholesterolemic agents and pharmaceutical compositions of the same.

DABCO effect on the photodegradation of photochromic compounds in spiro[indoline-pyran] and spiro[indoline-oxazine] series

Abstract: Photochromic compounds are involved in secondary oxidative reactios of photodegradation leading to the loss of their properties. The analytical studies of this process in toluene solution of both photochromic molecules, i.e. the 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,2′-[3H]naphth[2,1-b]pyran] and the 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]-naphth[2,1-b][1,4]oxazine], have allowed us, by identification of the main photoproducts, to propose some mechanisms for the oxidative degradation processes which occured by radical structures or singlet oxygen. In order to prove the implication of this last species in the degradation process, we have tested the effect of a singlet oxygen quencher with experimental spectrophotometric apparatus: the 1,4-diazabicyclo[2,2,2]octan (DABCO) which exhibits an important increase of the fatigue resistance of photochromic compounds. This quantitative aspect of the DABCO effect has been completed by a qualitative degradation approach concerning a comparative analytical study by gas chromatography between degradation of photochromic compounds with and without DABCO. In those conditions we have observed a significant change in the chromatographic profiles.

Synthetic reactions of 2-(2-amino-3-cyano-4H-[1]benzopyran-4-yl)propane-1,3-dinitrile with reactive methylene compounds

Abstract: Derivatives of dibenzo [b,d]pyran, [1]benzopyrano[2,3-b]pyridine, [1]benzopyron[3,4-c]pyridine and [1]benzopyrano[4,3,2-de][1,6]naphthyridine are obtained from the reaction of 2-(2-amino-3-cyno-4H-[1]benzopyran-4-yl)propane-1,3-dinitrile with compounds containing a reactive methylene group. Consideration of these reactions suggests that the dicyanomethyl group is released from the 4-position of the starting material, and that it mean reacts at the 2-position of the newly formed iminium ion. The 4-position is now available for Michael addition of a compound containing a reactive methylene group, but the nature of the final product depends on the substituents on the methylene group.

Pharmaceutical preparations which inhibit hepatitis B virus (HBV) replication

Abstract: On the basis of the present invention in relation with inhibiting hepatitus B virus replication, the pharmaceutical preparations containing the iridoid compounds are represented by the following structural formula(1), wherein, R1 is H or OH, R2 is H or COOR6 (R6 is H or lower alkyl), R3 is H or β-D-glucose, R4 is OH, CH 2 OH or 4-phenylpropionyloxy group, R5 is H, OH or O-glucose, C7-C8 shows single bond or double or ##STR1## (epoxy bond) In the above formula, the compound indicates Aucubin, Catapol, Geniposide, Rehmannioside, Harpagoside, Harpagide and Genipin. Meanwhile, Gardenoside and Swertiamarin such as other iridoids mentioned above are also expected to produce antiviral effect on HBV replication, since they possess the similar chemical structure and other pharmacological characteristics such as liver-protective activities against hepatic damages caused hepatotoxic substances and inhibitory effects on RNA and protein biosyntheses. The iridoid compounds according to the present invention are characterized by the structure of cyclopenta|C|pyran monoterpenoid, generally found as glycoside in nature. When subjected to β-glucosidase hydrolysis, aglycones are produced, and become biologically effective, exhibiting inhibitory effects on hepatitus B virus replication.

Pyran derivatives XIX. (Dialkylamino) substituted 1-benzopyranones and naphthopyranones with platelet antiaggregating activity.

Abstract: 2-(Dialkylamino)chromones 4 and 4-(1-piperazinyl)coumarins 11, as well as their angular benzo-fused derivatives 1, 2 and 12, 13, respectively, were synthesized and tested in vitro for their inhibitory activity on human platelet aggregation induced in platelet-rich plasma by ADP (5.0 microM), collagen (10.0 micrograms/ml), and A 23187 (calcimycin) (20.0 microM). Among the dialkylamino substituents used, and the ring systems examined, 1-piperazinyl and 1-benzopyran or naphtho[2,1-b]pyran, respectively, resulted the most effective ones for antiplatelet activity, both in the chromone and coumarin fields. 7-Ethoxy-4-(1-piperazinyl)coumarin 11b showed the highest activity, and higher than those of all reference compounds (ASA, trifluoperazine, propranolol, and dipyridamole) towards all platelet aggregation inducers.

Intramolecular 1,3-dipolar cycloaddition at the periphery of heterocyclic systems. Part 1. Facile oxime–nitrone isomerisation at the periphery of pyran and 1-benzopyran

Abstract: 4-(Alk-2-enylamino)-2-oxo-2H-1-benzopyran-3-carbaldehyde oximes 5 underwent thermally induced 1,3-dipolar cycloaddition under mild conditions giving isoxazolo[3,4-d][1]benzopyrano[4,3-b]pyridine derivatives 6 in good yields. The features of the oxime–nitrone isomerisation and nitrone–olefin cycloaddition are discussed.

Hetero-diels-alder reactions of dimethyl 1-oxo-(e,e)-2,4-hexadienephosphonate with 2-alkylidene-1,3-dithianes

Abstract: The cycloaddition reactions of dimethyl 1-oxo-(E,E)-2,4-hexadiene phosphonate (1) with 2-alkylidene-1,3-dithianes 4 and 5 gave [1]oxa-[7,11]dithiaspiro-[5,5]undecene-2-phosphonate derivatives. The reactions were responsive to electrophilic assistance by the solvent as well as ‘conventional’ Lewis Acid catalysis. The structural constitutions and preferred conformations of these pyran derivatives were established by NMR spectroscopy as well as by the X-ray crystallographic determination of a key derivative. In addition to E- to Z-double bond isomerization reactions in 1 and acyl chloride 2, αacyl phosphonate 1 underwent thermal isomerization to dimethyl 2H-pyran-6-phosphonate (6).

Hetero‐Diels‐Alder Additions of α,β‐Unsaturated‐Acyl Cyanides. Part 3. Syntheses of 3‐bromo‐2‐ethoxy‐3,4‐dihydro‐2H‐pyran‐6‐carbonitriles, and about their transformation to 2‐ethoxy‐2H‐pyrans

Abstract: Cycloadditions of the α,β-unsaturated-acyl cyanides 1–3 with (Z)-or (E)-1-bromo-2-ethoxyethene (4) may be performed at moderate temperatures and provide in good yields the 3-bromo-2-ethoxy-3,4-dihydro-2H-pyran-6-carbonitriles 5–7, respectively (Scheme 1). Diastereoisomeric pairs of products result at room temperature merely from the ‘endo’- and ‘exo’-transition states; more complex mixtures appear above 60° as a consequence of (Z)/(E)-isomerization of 4. The relative stability of the anomers of 5 and 6 is explored by treatment with BF3·Et2O. Acid alcoholysis (MeOH or EtOH) of 5 leads to acetals 9a, b of 4-bromo-5-oxopentanoate. Alkyl (2Z,4E)-5-ethoxypenta-2,4-dienoates 12, 17, and 20, are formed in alcoholic alkoxide solutions from 5, 6, and 7, respectively, which is compatible with the intermediacy of 2-alkoxy-2H-pyrans and their valence tautomers, α,β-unsaturatedacyl cyanides. Methoxide addition to the CN group competes with dehydrobromination in case of 5; it leads to 3-bromo-3,4-dihydro-2H-pyran-6-carboximidate 13 (ca. 50% at −20°) which can be hydrolyzed to the methyl carboxylate 14. DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) in benzene converts 5 to 6-ethoxy-2-oxohexa-3,5-dienenitrile (11), the ring-opening product of an obviously unstable 2-ethoxy-2H-pyran; the same reagent dehydrobrominates 6 to 2-ethoxy-4-methyl-2H-pyran-6-carbonitrile (15). HBr Elimination from 7 takes place with great ease in presence of pyridine, or even during chromatography on alumina, and leads to the stable ethyl 6-cyano-2-ethoxy-2H-pyran-4-carboxylate (18); this dimerizes at room temperature to give a 1:3 mixture of tricyclic adducts ‘endo’-21 and ‘exo’-21. The structure of the latter is established by an X-ray crystallographic analysis.

SYNTHESIS AND SOME REACTIONS OF NEW BENZO[b]PYRAN DERIVATIVES

Abstract: Reaction of cinnamonitriles 1a,b with 3-aminophenol (2a) or resorcinol (2b) gave the corresponding benzo[b] pyran derivatives (3a-d). Compound (3a) reacted with benzaldehyde to yield monobenzyli-dencamino derivative 4. Also, reaction of (3a) with benzenesulsulphonyl chloride gave 2-amino-3-cyano-4-phenyl-7-phenylsulphonylamido-4H-benzo[b]pyran (6) which, in turn, underwent some reactions to produce new benzo[b]pyrano[6,5-d]pyrimidine derivatives (7, 9) and (10).

Enzymatic synthesis of optically active (S)-(+)-2-hydroxymethyl-3,4-dihydro-2H-pyran and (S)-(+)-2-acetoxymethyl-3,4-dihydro-2H-pyran

Abstract: Porcine pancreas lipase(PPL)-catalyzed acetylation of (±)-2-hydroxymethyl-3,4-dihydro-2 H -pyran with vinyl acetate in organic solvent afforded ( S )-(+)-2-acetoxymethyl-3,4-dihydro-2 H -pyran. Alternatively, (±)-2-acetoxymethyl-3,4-dihydro-2 H -pyran was resolved via hydrolysis catalyzed by PPL in acetone-phosphate buffer system to afford ( S )-(+)-2-hydroxymethyl-3,4-dihydro-2 H -pyran with high enantiomeric purity.

Photocolouration of 2,4,4,6-tetraaryl-4h-pyrans and their heteroanalogues : importance of hypervalent photoisomers

Abstract: Molecular geometries of 2,4,4,6-tetraphenyl-4 H -pyran ( Ia ), 4,4-(biphenyl-2,2e-diyl)-2,6-diphenyl-4 H -pyran ( Ib ) and their heterocyclic isomers II - V were optimized by the PM3 method and used for the calculation of electronic absorption spectra by the CNDO/S-CI procedure. Comparison of the theoretical data with experimental UV-VIS absorption spectra made possible to select hypervalent molecules IIIa , IIIb , IVa and IVb being responsible for the photocolouration of 4 H -pyrans Ia , Ib , while compounds Va , Vb , VI and VII come into account as possible photodegradation products. The bleaching process of the UV illuminated compound Ia is analyzed in terms of dispersive first-order reaction kinetics.

Structural Properties Required for Two-photon Photochromism of Pyran Derivatives

Abstract: The photochromism of two new photochromic quinone monomethide derivatives was examined. While the 12aH-12a-methylnaphtho[3,2]chromene underwent a two-photon photochromic reaction, only a single-photon photochromic reaction between a keto form and an oxabicylcohexene form was observed for the phenanthrene analog.

A Novel Synthesis of Pyrano(2,3-d)pyrimidine Derivatives

Abstract: A ready one-pot preparation for pyrano[2,3-d]pyrimidines from appropriately substituted pyran derivative and N,N-dimethyldichloromethyleniminium chloride (phosgeniminium chloride) is reported.

Novel substituted phenanthropyrans

Abstract: Described are novel reversible photochromic phenanthropyran compounds, exemples of which are substituted 2H-phenanthro[4,3-b]pyran and 3H-phenanthro[1,2-b]pyran compounds. The 2H-phenanthropyran compounds have certain substituents at the number 5 and 6 carbon atoms of the phenanthro portion of the phenanthropyran and at the 2 position of the pyran ring. Certain substituents may also be present at the mumber 7, 8, 9, 10, 11, or 12 carbon atoms of the phenanthro portion of the phenanthropyran. The 3H-phenanthropyran compounds have certain substituents at the number 11 and 12 carbon atoms of the phenanthro portion of the phenanthropyran and at the 3 position of the pyran ring. Certain substituents may also be present at the number 5, 6, 7, 8, 9, or 10 carbon atoms of the phenanthro portion of the phenanthropyran. Also described are polymeric organic host materials that contain or that are coated with such compounds. Articles such as ophthalmic lenses or other plastic transparencies that incorporate the novel phenanthropyran compounds or combinations thereof with complementary photochromic compounds, e.g., spiro(indoline) type compounds, chromenes, and certain benzopyrans, are also described.