Showing papers on "Pyran published in 1990"

New carbazole alkaloids from Murraya euchrestifolia Hayata.

Abstract: Five new monomeric carbazoles, named eustifoline-A (1), -B (2), -C (3), and -D (5) and furostifoline (6), and one dimeric carbazole alkaloid, murrastifoline-E (7), were isolated from the root bark of Murraya euchrestifolia collected in Taiwan in December, and their structures were elucidated by spectrometric means. Eustifoline-A (1) and -B (2) have a substituted pyran ring, ad eustifoline-C (3) having a geranyl side chain is considered to be a biogenetic precursor of 2. Eustifoline-D (5) and furostifoline (6) both have a furan ring system and were shown to be structural isomers. The new dimeric carbazole murrastifoline-E (7) was found to have the structure corresponding to deoxygenated murrastifoline-D (8) and to be an adduct of murrayafoline-A (9) with girinimbine (10).

Structure-activity relationship of antiestrogens. Effect of the side chain and its position on the activity of 2,3-diaryl-2H-1-benzopyrans.

Abstract: A series of 2,3-diaryl-2H-1-benzopyrans carrying a tertiary aminoethoxy chain at the ortho, meta, or para position of 2-phenyl or an alkyl at position 4 of the pyran ring were synthesized and evaluated for their affinity for estrogen receptor (ER) and for microsomal antiestrogen specific binding site and for their uterotrophic-antiuterotrophic activities in rodents. The analogues bearing the side chain at the para position of 2-phenyl were found to be active while those substituted at the meta and ortho positions were inactive as ER ligands as well as estrogen agonists-antagonists. Among para-substituted ethers, the 2-piperidinoethoxy analogue 5 was found to be a more effective antiestrogen than the corresponding pyrrolidino, dimethylamino, and related analogues. Incorporation of a methyl or an ethyl at C4 in the pyran nucleus was found to increase receptor affinity of the prototypes. The ethyl was also found to potentiate agonist activity of the prototype while abolishing its antagonist activity. The piperidino analogue 5 was found to be a better antiestrogen than tamoxifen as well as LY-117018 in rats as well as mice. The prototypes were also found to have high affinity for the microsomal antiestrogen specific binding sites. The benzopyrans have thus emerged as a new group of potent antiestrogens.

3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors. 6. Trans-6-[2-(substituted-1-naphthyl)ethyl(or ethenyl)]-3,4,5,6-tetrahydro-4-hydroxy-2H-pyran-2-ones.

Abstract: A variety of trans-6-[2-(substituted-1-naphthyl)ethyl(or ethenyl)]-3,4,5,6-tetrahydro-4-hydroxy-2H-pyran-2-ones were prepared and, upon conversion to their 3,5-dihydroxy carboxylates, were found to have good inhibitory activity against the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase, the rate-determining enzyme in cholesterogenesis. The most active compounds are 2,4,6- and 2,4,7-trichloro derivatives and would be expected to display about the same potency as the standard compactin upon resolution.

The photochemistry of pyran-4-ones: intramolecular trapping of the zwitterionic intermediate with pendant hydroxyl groups

Abstract: Pyran-4-ones bearing hydroxyalkyl side chains underwent efficient photocyclization to bicyclic oxyallyl zwitterions, and subsequent intramolecular nucleophilic trapping gave bicyclic cyclopentenone ethers in good to excellent yield

Preparation and Diels–Alder reactivity of thieno[2,3-c]-and thieno[3,2-c]-pyran-3-ones. Stable 2,3-dimethylenethiophene derivatives; synthesis of benzothiophenes

Abstract: The thieno[2,3-c]pyran-3-ones (7) and the isomeric [3,2-c]pyranones, eg(26) are stable derivatives of 2,3-dimethylenethiophene (3) When heated with alkynes they undergo Diels–Alder reaction to give, after loss of carbon dioxide, benzothiophenes With unsymmetrical alkynes, the Diels–Alder reactions exhibit varying degrees of regioselectivity Intramolecular Diels–Alder reactions of the thieno[2,3-c]pyran-3-ones (17) and (21) give cycloalka[g]- and cycloalka[e]-benzothiophenes respectively

Reformatskii reaction on .alpha.-oxo ketene dithioacetals: synthesis of substituted and fused ethyl 2-hydroxy-6-(methylthio)benzoates, 6-(methylthio)pyran-2-ones, and 6-(methylthio)-2(1H)pyridone derivatives

Abstract: diluted with water and extracted with ether. The ethereal phase was washed with water, 5% Na2S203 (aqueous), 5 % KHCOB (aqueous), and water and dried with Na2S0,, and the solvent was evaporated in vacuo. The residue was dissolved in a petroleum ether-benzene mixture (2: l ) and filtered through a pad of aluminum oxide. The filtrate was evaporated, and the product was crystallized from aqueous methanol to give 6@,19-epoxycholest4-en-3p-yl acetate (24 mg): mp 57-59 OC; [a]D -900 ( c 1.5); 1~ NMR 0.72 (9, 3 H, 18-H), 2.02 (s, 3 H, CH,CO,), 3.37 and 4.12 (AB system, J = 8 Hz, 2 H, 19-H), 4.48 (d, J = 4 Hz, 1 H, 6a-HI, 5.23 (m, W/2 = 8 Hz, 1 H, 3a-H), 5.57 ( 8 , 1 H, 4-H).

Methyl 2-Benzoylamino-3-dimethylaminopropenoate in the Synthesis of Heterocyclic Systems. The Synthesis of Substituted 3-Benzoylamino-2H-pyran-2-ones

Abstract: 5,6-disubstituted 3-benzoylamino-2H-pyran-2-ones 3 are prepared either from 1,3-dicarbonyl compounds 1 and methyl 2-benzoylamino-3-dimethylaminopropenoate (2) in an one-step reaction, or from ethyl 2-acyl-3-dimethylaminopropenoates 5a,b or 2-(dimethylamino)methylene-1,3-diketones 5c,d and 5-oxo-2-phenyl-1,3-oxazole 6

Preparation and Diels–Alder reactivity of benzothieno[2,3-c]- and benzothieno[3,2-c]-pyran-3-ones, benzothiophene-2,3-quinodimethane analogues; synthesis of dibenzothiophenes

Abstract: The benzothieno[2,3-c]pyran-3-ones (6) and the isomeric [3,2-c] pyranones (7) are stable analogues of benzothiophene-2,3-quinodimethane (3). When heated with alkynes they undergo Diels-Alder reactions to give, after loss of carbon dioxide, dibenzothiophenes. The regiochemistry of the Diels–Alder reaction is discussed.

Reactions of ortho-quinones with ethoxycarbonylmethylene(triphenyl)-phosphorane. Trapping of the ortho-quinone methanide intermediates

Abstract: The reactions of the ortho-quinones (5a-d) with the phosphorus ylide (6) afforded, besides the expected coumarin derivatives (10a–d), compounds (9d), (11b and c), (13), and (14). When the reactions between compounds (5a–d) and (6) were carried out in the presence of ethyl vinyl ether (20) the pyran derivatives (21 a,b, and d) and (22a, b, and d) were obtained as main products, by a [4 + 2] trapping process of the ortho-quinone methanide intermediates (7a, b, and d) with the dienophile (20). Similarly, the reaction between compounds (5a) and (6) in the presence of α-methylstyrene afforded mainly the pyrans (23 I and II). Compounds (16), (19), and (24) were also prepared and studied.

An Efficient Baeyer-Villiger Approach to 6-(Hydroxymethyl)tetrahydro-2H-pyran-2-one Derivatives

Abstract: An efficient (64 % overall yield) five step preparation of 6-(tert-butyldiphenylsiloxymethyl)tetrahydro-2H-pyran-2-one from ethyl 2-oxocyclopentane carboxylate is reported

Oligomeric flavanoids. Part 7. Novel base-catalysed pyran rearrangements of procyanidins

Abstract: Procyanidin B-3 (1) is subject to readily occurring C-ring isomerizations in NaHCO3–Na2CO3 buffer solution to form a novel 8,9-cis-9,10-trans-3,4,9,10-tetrahydro-2H,8H-pyrano[2,3-h]chromene (3) and a series of 2,3-cis-3,4-trans-4-aryl-2-flavanylbenzopyrans (6), (9), and (12) in which the C-2 pyrocatechol and C-4 (+)-catechin moieties are interchanged relative to their positions in the biflavanoid (1). These compounds presumably originate via 1,3-aryl migrations in intermediate quinone-methides with concomitant inversion of the absolute configuration at C-3. The lability of the interflavanyl bond at alkaline pH is reflected by the presence of considerable quantities of (+)-catechin as well as high-molecular-mass analogues of precursor (1).

Polar effects in the decomposition of bis(3-alkoxyaroyl) peroxides. Synthesis of 8-alkoxy-6H-dibenzo[b,d]pyran-6-ones

Abstract: The reaction of four substituted bis(3-alkoxybenzoyl) peroxides (1b-e) in neat phenols (2a-e) affords mainly 8-alkoxy-6H-dibenzo[b,d]pyran-6-ones (7) and ortho-benzoyloxylation products (4) of the phenol. Diaroyl peroxides without electron-releasing meta substituents afford essentially products 4. A mechanism involving monoelectronic oxidation of the phenol by the peroxide and biaryl coupling by preferential addition of the phenol radical cation to the ortho positions to the alkoxy group of the diaroyl peroxide is suggested

Synthesis and bioactivity of propranolol analogues with a rigid skeleton. I.

Abstract: The synthesis of two kinds of propranolol analogues, A and B, with a rigid skeleton was investigated. The compounds were designed to help identify the conformation involved in β-adrenergic receptor-propranolol interaction. The key intermediate, 2-hydroxy·2, 3-dihydronaphtho[1, 8-bc]pyran (5), was obtained starting from acenaphthenone (1). On sequential dehydration, hydroboration, and oxidation, 5 gave 2, 3-dihydronaphtho[1, 8-bc]pyran-3-one (8), which was converted to compound A. Compound 5 was also derived to 2-formyl-2, 3-dihydronaphtho[1, 8-bc]pyran (13) via the 2-vinyl compound (12). Condensation of nitromethane with 13 followed by reduction and alkylation produced the desired compound B. The β-blocking activities of A and B were examined.

2H,5H-[1]benzothiopyrano [4,3-b]pyran derivatives with platelet antiaggregating activity.

Abstract: The synthesis of some N,N-disubstituted 4-amino-3-phenyl-2H,5H-[1]benzothiopyrano [4,3-b]pyran-2-ones by reaction of phenylchloroketene with a series of N,N-disubstituted 3-aminomethylene-2,3-dihydro-4H-1-benzothiopyran-4-ones, followed by dehydrochlorination of the primary adducts with DBN, is described. Some of these compounds showed a strong platelet antiaggregating activity in vitro, superior to that of acetylsalicylic acid.

Oligomeric flavanoids. Part 11. Structure and synthesis of the first phlobatannins related to (4α,6:4α,8)-bis-(–)-fisetinidol-(+)-catechin profisetinidin triflavanoids

Abstract: Several members of the unique class of natural phlobatannins, representing the products of stereospecific pyran rearrangement of 2,3-trans-3,4-trans-flavan-3-ol units present in, e.g., (4α,6 : 4α,8)-bis-(–)-fisetinidol-(+)-catechin triflavanoid profisetinidins, have been characterized. These include the functionalized 6,7-trans-7,8-cis-10,11-trans-11,12-cis-hexahydrodipyrano[2,3-f : 2′,3′-h]chromene (3) and the 10-flavanyl-6,7-trans-7,8-cis-tetrahydropyrano[2,3-f]chromene ‘isomerization-intermediates’(6), (15), and (17). The proposed structures of compounds (3) and (6) were confirmed by synthesis via base-catalysed conversion of the 3-O(E)-methyl ether (1) of its apparent biogenetic precursor, and the relative nucleophilicity of the A- and D-ring in the ‘dimeric’ tetrahydropyrano[2,3-h]chromene (14) assessed by condensation with the flavan -3,4-diol, (+)-mollisacacidin.

A Facile and Convenient Synthesis of (E,E)-4-Trifluoroacetyl-1,3-butadienyl Sulfides by Acid Catalyzed Reaction of 2,4-Diethoxy-6-trifluoromethyl-3,4-dihydro-2H-pyran with Thiols

Abstract: (E,E)-4-Trifluoroacetyl-1,3-butadienyl sulfides are prepared from 2,4-diethoxy-6-trifluoromethyl-3,4-dihydro-2H-pyran with thiols in the presence of acid catalysts.

A Simple Synthesis of Naphtho[1,8-bc]pyran

Abstract: Naphto[1,8-bc]pyran is prepared in three steps in 40% overall yield from acenaphthenone by oxidation with 3-chloroperoxybenzoic acid, reduction of the resultant lactone with diisobutylaluminum hydride, and dehydration of the lactol thus obtained with mesyl chloride/triethylamine

Synthesis of some biologically active derivatives of 2-hydroxymethyl-5-hydroxy-4H-pyran-4-one

Abstract: Depending on reaction conditions, acylation of the phenolic and primary alcoholic group in 2-hydroxymethyl-5-hydroxy-4H-pyran-4-one leads to mono- or disubstituted products. Also described is acylation of the phenolic group in 2-chloromethyl- or 2-bromomethyl-5-hydroxy-4H-pyran-4-one as well as the nucleophilic replacement of the halogen by azide group. The prepared derivatives exhibit herbicidal and growth regulatory activity