Showing papers on "Pyran published in 1985"

Trans-6-[2-(substitutedpyrrol-1-yl)alkyl]-pyran-2-one inhibitors of cholesterol synthesis

Abstract: 6-[2-(Substituted-pyrrol-1-yl)alkyl]pyran-2-ones and the corresponding ring-opened hydroxy-acids derived therefrom are potent inhibitors of the enzyme 3-hydroxy-3-methylglutarylcoenzyme A reductase (HMG-CoA reductase), and are thus useful hypolipidemic and hypocholesterolemic agents. Pharmaceutical compositions containing such compounds, and a method of treatment employing such pharmaceutical compositions are also disclosed.

Ring transformation of isoxazoles into furan and pyran derivatives

Abstract: A ring transformation of isoxazole into 3,5-dicyano-4H-pyran-2-amines (4) and N-arylidenefuran-2-amines (7) is reported. It involves a ring opening of the isoxazole ring in the presence of an aromatic aldehyde, leading to 2-arylidene-3-oxopropanenitrile (2), followed by nucleophilic attack by either cyanide or propanedinitrile and then heterocyclization. The reaction can also be applied to 5-substituted isoxazoles.

Analogs of cannabinoids: synthesis of some 7H-indolo-, 5H-imidazolo, 7H-benzimidazolo[1,2-c] [1,3]benzoxazines – novel ring systems

Abstract: Tetrahydrocannabinol 1, the active constituent of CannabissativaLinn, is a well-known CNS-active compound and introduction of a nitrogen atom at the ring junction of the pyran and alicyclic ring is...

Cycloaddition of 2H-pyran-2-thiones with nitroso derivatives: an unexpected cycloaddition-rearrangement reaction

Abstract: Reaction of pyran-2-thiones 4 with nitroso derivatives led surprisingly to type-8 (19) adducts which proved to be isomeric with the initially expected primary Diels-Alder cycloadducts 5. Methyl 2-thioxo-2H-pyran-5-carboxylate (4f), when reacted with nitrosobenzene at -10°, led quantitatively to the thieto-oxazine intermediate 13, which turned out to be the cornerstone of the complex cycloaddition-rearrangement 5 8 reaction pathway (Scheme 3). Differential scanning calorimetry, as performed for the 18a 19a conversion, permitted to demonstrate that this multistep rearrangement is overall a higly exothermal process, the final product 19 representing an energy-sink along this reaction pathway.

Method for preparing spiro(indoline)-type photochromic compounds

Abstract: Spiro(indoline)-type photochromic compounds are prepared by admixing a solution of the Fischer's Base reactant in non-polar solvent with a mixture of the pyran- or oxazine-forming reactant, e.g., 5-nitroso-6-hydroxy quinoline, in polar solvent and heating the resulting reaction medium at temperatures sufficient to form the corresponding spiro(indoline)-type compound while simultaneously removing co-product water.

13C NMR spectra of 2‐amino‐4H‐pyran derivatives

Abstract: The 13C NMR spectra of sixteen 2-amino-4H-pyran derivatives, consisting of seven 3-cyano, two 5-cyano and seven 3,5-dicyano derivatives, are reported. For the purposes of comparison, 13C NMR data for 2,6-dimethyl-3,5-dicyano-4-phenyl-4H-pyran are also given.

Chlorosulfate and azidosulfate esters of tetrahydro-2H-pyran-2-yl-methanol

Abstract: Sulfamates of the following formula (I): ##STR1## wherein X is O or CH2 and R1, R2, R3, R4 and R5 are as herein defined have been found to exhibit anticonvulsant activity and are thus useful in the treatment of conditions such as epilepsy. Further, pharmaceutical compositions containing a compound of formula (I) as well as methods for their use and intermediates form part of the present invention.

β-Halogeno ether synthesis of olefinic alcohols: stereochemistry and conformation of 2-substituted 3-halogenotetrahydro-pyran and -furan precursors

Abstract: Ring-scission of cis- or trans-2-alkyl-(or aryl-) 3-chlorotetrahydropyrans proceeds regioselectively and highly stereoselectively to give (E)-alk-4-en-1-ols, but in the parallel tetrahydrofuran series (Z)-/(E)-mixtures, dependent on precursor geometry, are formed. In this paper the stereochemistry and conformation of the tetrahydro-pyran and -furan precursors are considered. The cis/trans-composition of 2,3-dihalogenotetrahydro-pyrans and -furans made by various routes is reported. Reaction with Grignard reagents gives separable cis-/trans-mixtures the stereoisomeric composition of which, in the cases examined, does not depend on the stereoisomeric composition of the dihalide, but does vary with the halogen and the composition of the Grignard or dialkylmagnesium; possible reasons are discussed.The stereochemistry and conformation of the 2-alkyl-(or aryl-)3-chlorotetrahydropyrans is analysed by n.m.r. methods (J2a,3ecis ca. 1.5 Hz; J2a,3atrans ca. 9.8 Hz) but assignments for the two tetrahydrofuran series with J2.3 2.6–3.6 and 4.3–5.9 are made uncertain by pseudorotation. The stereochemical identity of the two series is rigorously proved by isolation of cis- and trans-2-allyl-3-chlorotetrahydrofuran. On the one hand the former is hydrogenated to the cis-2-propyl compound, correlated with other members of the alkyl series, but on the other it is oxidised and the acid is converted into the cis-p-bromophenacyl ester. The stereochemistry and conformation of the latter is rigorously demonstrated by an X-ray structure.The stereochemistries and conformations of the 2-deuterio- and 2-methoxy-3-chlorotetrahydropyrans are discussed, and consideration is then extended to the 2-alkyl-3-chloro-2-methyltetrahydro-pyran and -furan series.

Annelation reaction of levoglucosenone. Chiral intermediates for the synthesis of naphtho[2.3-c]pyran-5,10-quinone antibiotics

Abstract: Reaction of the anion of 3-cyano-4-methoxy-3H-isobenzofuran-1-one (4b) with levoglucosenone affords a chiral annelation products useful for the synthesis of naphtho[2.3-c]pyran-5,10-quinone antibiotics.

A synthesis of (+)-milbemycin β3. The 3,4-dihydro-2H-pyran approach

Abstract: Nucleophilic scission of oxirane (8) by vinyl alanate (4) and oxirane (11) by metallated 3,4-dihydro-2H-pyran (15) were key steps in the synthesis of (+)-milbemycin β3(1)

Reaction of γ-pyrones with 1,3-bis(dicyanomethylene)indan

Abstract: The condensation of γ-pyrones with 1,3-bis(dicyanomethylene)indan leads to the corresponding deeply colored 2-(pyran-4-ylidene)-1,3-bis(dicyanomethylene)indans. The reaction of the latter with primary aliphatic or aromatic amines leads to replacement of the pyran oxygen by an amino group. The resulting compounds are zwitterions and possesses dichroic properties. The IR and UV spectra, and also the dichroic spectra of the compounds obtained in a liquid crystal are given. A qualitative explanation of the nature of the absorption bands of these compounds in the visible region of the spectrum is presented.

New synthetic routes to spiroacetals. The 3,4-dihydro-2H-pyran approach to (±)-talaromycin B

Abstract: The nucleophilic cleavage of the oxirane (9) by the organocuprate derived from 3-ethyl-6-lithio-3,4-dihydro-2H-pyran (7) was the key step in a synthesis of racemic talaromycin B (12). A similar synthesis of desethyltalaromycin B (15) from (9) and 6-lithio-3,4-dihydro-2H-pyran was achieved.

Process for epimerization at C6 of 3,4,5,6-tetrahydro-2H-pyran-2-one

Abstract: An external bond at the 6-position of a 3,4,5,6-tetrahydro-2H-pyran-2-one, as found in the 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, is readily epimerized by treating an amide of the corresponding hydroxy acid with a sulfonyl chloride reagent.

The reaction of cyclopropenethione with carbonyl-stabilized phosphonium methylides to yield 2H-pyran-2-thione.

Abstract: The reaction of diphenylcyclopropenethione with carbonyl-stabilized triphenylphosphonium methylides (2) to yield 2H-pyran-2-thiones was studied. It was clarified that electron-releasing substituents increased the reactivity of 2.

The microwave spectrum of 3,4-dihydro-1,2-pyran

Abstract: Abstract The rotational transitions of 3,4-dihydro-1,2-pyran in the ground state and six vibrationally excited states have been assigned. The rotational constants for the ground state (A = 5198.1847(24), B = 4747.8716(24) and C = 2710.9161(24) have been derived by fitting μa, μb and μc-type transitions. The dipole moment was determined from Stark displacement measurements to be 1.400(8) D with its principal axis components |μa| =1.240(2), |μb| = 0.588(10) and |μc| = 0.278(8) D. A model calculation to reproduce the ground state rotational constants indicates that the data are consistent with a twisted ring conformation. The average intensity ratio gives vibrational separations between the ground and excited states of the ring-bending and ring-twisting modes of ~ 178 and ~ 277 cm-1 respectively.

Friedel–crafts reaction of 3,6-dihydro-4-methyl-2h-pyran with phenols. a convenient synthesis of a key intermediate of alpha-tocopherol

Abstract: The Friedel–Crafts reaction of 3,6-dihydro-4-methyl-2H-pyran with 2,3,5-trimethylhydroquinone afforded 3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-ethanol in good yield.

New pyran derivatives as well as a process for preparing them.

Abstract: The invention relates to pyran derivatives of formula: in which X1 represents H, Cl or Br and Z is one of the groups: in which X2 represents H, Cl or Br, T represents O or S and Y is an arabinose, xylose or ribose residue, the acetylated form of this residue of pyran or furan configuration, attached to the R residue of the molecule to give either the alpha anomer or the beta anomer, as well as a process for preparing these compounds.

4,4-Dimethyl tetrahydro-2H-pyran-2-on derivatives, process for their preparation and their use for the preparation of cyclopropanic derivatives

Abstract: 1. In all their possible isomeric forms, the compounds with the formula 1 : see diagramm : EP0153212,P12,F1 in which X represents a nucleofige group chosen from the group constituted by halogen atoms, the radicals : see diagramm : EP0153212,P12,F1 in which R' represents an alkyl radical containing from 1 to 18 carbon atoms or R' represents an aryl radical containing from 6 to 14 carbon atoms and the radicals : see diagramm : EP0153212,P12,F1 in which R2 and R3 , identical or different, represent an alkyl radical contraining from 1 to 18 carbon atoms or an aryl radical containing from 6 to 14 carbon atoms and R represents a hydrogen atom or the carbonated residue of a chiral or non-chiral alcohol ROH, as well as all the possible mixtures of these isomers.

Non-cytotoxic activity of pyran copolymer-induced macrophages associated with potentiation of tumour vaccine in recipient mice.

Abstract: Mice inoculated with both L1210 murine tumour vaccine and pyran copolymer were more resistant to L1210 than those inoculated with either of these agents alone. Rabbit anti-mouse thymocyte globulin and silica reduced the augmented resistance of these mice, suggesting the involvement of activated anti-tumour T cells and macrophages in the augmented resistance. We studied the activation of these two cells separately and examined the possible contribution of pyran copolymer-induced peritoneal cells to the augmented resistance to an inoculation of live tumour. Pyran copolymer-induced peritoneal cells endowed the tumour vaccine-primed mice, but not unprimed mice, with resistance to implanted L1210 and, among those peritoneal cell populations, macrophages but not T cells were responsible for this effect since the activity was associated with a cell population which was (1) adherent to nylon wool columns, (2) sensitive to silica and (3) insensitive to anti-Thy 1.2 antibody plus complement. The pyran copolymer-induced peritoneal cells had very little antiproliferative activity when tested against L1210 in vitro and mice inoculated with these peritoneal cells did not survive a challenge of live L1210 cells much longer (<1 day) than L1210 inoculated control mice. Furthermore, the survival of L1210 vaccine-primed mice inoculated with one-tenth the amount of live L1210 (102) was still much shorter than that of mice primed with L1210 vaccine plus pyran copolymer and challenged with ten times as many (103) live L1210 cells. Therefore, direct tumouricidal activity was probably not a major factor in the in vivo immunological augmenting activity of the pyran copolymer-induced macrophages.

Synthesis of hexaacetyltetrahydroaucubin A

Abstract: The synthesis of hexaacetyltetrahydroaucubin A, (1S,4aR,5R,7S,7aR)-5-acetoxy-7-acetoxymethyl-1-(2,3,4,6-tetraacetyl-β-D-glucopyranosyloxy)octahydrocyclopenta[c]pyran, has been carried out.