HETEROCYCLES

■ Contents

■ A New Route to Papaverine Analogs via Photocyclization of Substituted N-Acyl-α-dehydrophenylalaninamides

Hideki Hoshina, Kei Maekawa, Keisuke Taie, Tetsutaro Igarashi, and Tadamitsu Sakurai*

*Departmnet of Applied Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan

Abstract

(Z)-N-Phenylacetyl-α-dehydro(3,4-dimethoxyphenyl)alaninamide derivatives [(Z)-1] were prepared in satisfactory yields, starting from 3,4-dimethoxybenzaldehyde. On irradiation in methanol, regioselective photocyclization of these derivatives proceeded to give papaverine analogs in good yields. Substituents introduced into (Z)-1 were found to exert only a minor effect on the conversion of the starting isomers (1) as well as on the selectivity of the analogs which were formed along with 1-azetines.

■ (7R,8S) and (7S,8R) 8-5’ Linked Neolignans from Egyptian Herbal Medicine Anastatica hierochuntica and Inhibitory Activities of Lignans on Nitric Oxide Production

Masayuki Yoshikawa,* Toshio Morikawa, Fengming Xu, Shin Ando, and Hisashi Matsuda

*Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan

Abstract

Three new (7R,8S) and (7S,8R) 8–5’ linked neolignans named hierochins A (1), B (2), and C (3) were isolated from an Egyptian herbal medicine, the whole plants of Anastatica hierochuntica. The absolute stereostructures of new compounds were elucidated on the basis of chemical and physicochemical evidence. Both enantiomers, (7R,8S) and (7S,8R)-type neolignans, were found to coexist in a state of a little differing functional structure. The effects of isolated lignans on nitric oxide production in lipopolysaccharide-activated macrophages were examined and three known neolignan constituents were found to show inhibitory effects on nitric oxide production and induction of inducible nitric oxide synthase.

■ Synthesis of 5-(4-Aryl)-2-phenyl-5,6-dihydrobenzo[b][1,5]oxazocin-4-ones

Yann Davion, Gérald Guillaumet, Jean-Michel Léger, Christian Jarry, Brigitte Lesur, and Jean-Yves Mérour*

*Instiut de Chimie Organique et Analytique, C.N.R.S., Unviersité d’Orléans, BP 6759, Rue de Chartres, 45067 Orleans Cedex, France

Abstract

Cyclization of N-aryl-N-(2-hydroxybenzyl)-3-phenylpropynamide in basic medium under the influence of a catalytic amount of Pd(0) afforded the eight-membered framework 5-(4-aryl)-2-phenyl-5,6-dihydrobenzo[b][1,5]oxazocin-4-ones.

■ A Simple Preparative Method of N-Arylindigos and Substitution Effect in UV/Visible Absorption

Yukihiro Matsumoto and Hitoshi Tanaka*

*Department of Optical Science and Technology, Faculty of Engineering, University of Tokushima, Minamijosanjima-cho, Tokushima 770-8506, Japan

Abstract

N-Aryl- and N, N’-diarylindigos were prepared by refluxing corresponding aryl iodides or bromide with indigo in o-dichlorobenzene. Variation of their UV/visible spectra with the ring-substitution was discussed on the basis of the captodative and steric effects.

■ Thermal Rearrangement of 3-Hydroxy-1H,3H-quinoline-2,4-diones to 3-Acyloxy-2,3-dihydro-1H-indol-2-ones

Antonín Klásek,* Kamil Koristek, Stanislav Kafka, and Janez Kosmrlj

*Faculty of Technology, Tomas Bata University in Zlín, 762 72 Zlín, Czech Republic

Abstract

3-Alkyl/aryl-3-hydroxy-1H,3H-quinoline-2,4-diones (2) were transformed into isomeric 3-acyloxy-2,3-dihydro-1H-indol-2-ones (3) by thermally induced molecular rearrangement. All products were characterized by their ¹H NMR, ¹³C NMR, and IR spectra.

■ A Convenient Diversification of Pyrrolo[2,3-b]quinolines by Iodonation and Palladium-catalyzed Coupling Reactions

Won Jung Lee, Moon Bae Gee, and Eul Kgun Yum*

*Department of Chemistry, College of Natural Sciences, Chungnam National University, Taejon 305-764, Korea

Abstract

The 2-trimethylsilylpyrrolo[2,3-b]quinolines were easily transformed into 2-iodopyrrolo[2,3-b]quinolines under NIS/CH₃CN. The palladium-catalyzed Heck, Stille, and Suzuki coupling reactions of 2-iodo[2,3-b]quinolines provided diverse 1,2,3-trisubstituted pyrrolo[2,3-b]quinolines in moderate to high yields.

■ Synthesis of (S)-Vasicol and (S)-3-Hydroxy-2-pyrrolidinone

Pei-Qiang Huang,* Xiao Zheng, and Hua Wei

*Department of Chemistry, Xiamen University, 422 Siming Nanlu, Xiamen, Fujian 361005, China

Abstract

Starting from (S)-malic acid, a flexible approach to (S)-3-hydroxy-2-pyrrolidinone and (S)-1-alkyl-3-hydroxy-2-pyrrolidinones was reported. Using this method, the first total syntheses of (-)-vasicol as well as deaminovasicol were accomplished, which allowed the revision and clarification the confusion about the structure of naturally occurring (-)-vasicol.

■ Stereoselective Conjugate Addition of Metallated 2-Methylpyridine to Functionalized α,β-Unsaturated Carbonyl Compounds

Francisco Sánchez-Sancho and Bernardo Herradón*

*Instituto de Química Orgánica General, C. S. I. C., Calle Juan de Cierva, 3, 28006 Madrid, Spain

Abstract

The reaction of bis-(2-pyridylmethyl)cyanocuprate (3) with a variety of α,β-unsaturated carbonyl compounds is reported. It has been found that while the reaction with enone goes through a 1,2-addition path, the outcome of the reaction with α,β-unsaturated esters depends on the structure of the electrophile, giving the conjugate addition product with γ-hetero-substituted α,β-unsaturated esters. On the other hand, the reaction of 3 with oxygenated butenolides is stereoselective, affording the 1,4-addition product.

■ Synthesis of 1,2-Benzisothiazolin-3-one by Transamination of Sulfenamides

Masao Shimizu,* Ayanobu Takeda, Hidenori Fukazawa, Yoshimoto Abe, and Isao Shibuya

*National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan

Abstract

N-Substituted sulfenamoylbenzoates were synthesized by transamination of N-unsubstituted sulfenamoylbenzoates with amines. The reaction did not always proceed by simple amine exchange between the amines and ammonia on the sulfur atom of the sulfenamides. In reactions with aliphatic amines, the sulfenamides cyclized to form N-substituted 1,2-benzisothiazolin-3-ones. The synthesis of 1,2-benzisothiazolin-3-ones by intramolecular transamination was also investigated by S-amination of 2-mercaptobenzamides.

■ Synthesis of (±)-Rolipram

Meng-Yang Chang,* Pei-Pei Sun, Shui-Tein Chen,* and Nein-Chen Chang*

*Institute of Biological Chemistry, Academia Sinica, 128, Yan-Chiu-Yuan Road, Sec II, NanKang, Taipei, 11529, Taiwan, R.O.C.

Abstract

A facile synthesis of rolipram via stepwise [3+2] annulation and desulfonated hydrolysis was reported. Base-induced coupling/cyclization reactions of α-sulfonylacetamide with (Z)-2-bromoacrylic ester yielded three contiguous centers on the pyroglutamate system with trans-trans orientation as the one-pot key step.

■ Pyridazine Derivatives and Related Compounds, Part 9. Tetrazolo[1,5-b]pyridazine-8-carbohydrazide Synthesis and Some Reactions

Ali Deeb* and Hosam Saad

*Department of Chemistry, Faculty of Science, University of Zagazig, Zagazig, Egypt

Abstract

The reaction of the hydrazide of 6,7-diphenyltetrazolo[l,5-b]pyridazine-8-carboxylic acid (3) with aromatic aldehydes gave 8-arylidenecarbohydrazide derivatives. The reaction of 3 with methanesulfonyl chloride, benzenesulfonyl chloride, phenyl and benzyl isothiocyanates afforded the corresponding N-substituted derivatives. The reaction of 3 with potassium ethylxanthate gave 5-(6,7-diphenyltetrazolo[l,5-blpyridazin-8-yl)-1,3,4-oxadiazole-2-thione (7). The alkylation of this product in an alkaline medium proceeds at the sulfur atom, while the aminomethylation and acylation proceed at the nitrogen atom. Compound (3) also reacted with N-aminothiosemicarbazide to give 4-amino-5-(6,7-diphenyl-tetrazolo[l,5-b]pyridazin-8-yl)-1,2,4-triazole-3-thione (11).

■ Constituents of the Leaves of Petasites formosanus and Their Antioxidative Activity

Chun-Hua Lin, Chia-Ying Li, Chang-Sheng Kuoh, and Tian-Shung Wu*

*Department of Chemistry, Natioanl Cheng Kung University, 1. Ta-Shiueh Rd., Tainan, 70101, Taiwan, R.O.C.

Abstract

Three new naturally occurring phenylpropenoyl derivatives, sodium dupracine (1), (E)-dupracine methyl ester (2), (Z)-dupracine methyl ester (3), together with eight known compounds, were isolated from the leaves of Petasites formosanus. Their structures were established by spectral methods and chemical transformations. The isolated compounds showed significant antioxidative activity in DPPH radical scavenging assay.

■ Facile Synthesis of Diarylpyrazines Using Suzuki Coupling of Dichloropyrazines with Aryl Boronic Acids

Nate Schultheiss and Eric Bosch*

*Department of Chemistry, Southwest Missouri State University, 901 South National Avenue, Springfield, MO 65804, U.S.A.

Abstract

The palladium-catalyzed coupling of dichloropyrazines with aryl boronic acids is reported. The reaction proceeds smoothly under anaerobic conditions to give moderate to good yields of the corresponding diarylpyrazines.

■ Ytterbium Triflate-catalysed Synthesis of Ethyl 1,2,3,4-Tetrahydroisoquinoline-1-carboxylates Using Ethyl Chloro(phenylselanyl)acetate

Huey-Min Wang, Iou-Jiun Kang, and Ling-Ching Chen*

*Graduate Institute of Pharmaceutical Sciences, Kaohsiung Medical University, 100 Shin Chuan 1st Rd., Kaohsiung 80708, Taiwan, R.O.C.

Abstract

The reaction of N-benzenesulfonyl-β-phenethylamines with ethyl chloro(phenylselanyl)acetate catalysed by ytterbium triflate provides a convenient methodology for the synthesis of ethyl 1,2,3,4-tetrahydroisoquinoline-1-carboxylates.

■ Structural Equilibrium and Ring-Chain Tautomerism of Aqueous Solutions of 4-Aminobutyraldehyde

Casper Struve and Carsten Christophersen*

*Marine Chemistry Section, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark

Abstract

NMR spectroscopy of aqueous solutions of 4-aminobutyraldehyde in the range 0 < pH < 13 established the occurrence of protonated and hydrated amino aldehydes in equilibrium with pyrrolines, and pyrrolinium salts.

■ A New Pyranocoumarin from Peucedanum praeruptorum

Ling-Yi Kong,* Yi Li, and Masatake Niwa

*Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, China

Abstract

A new dihydropyranocoumarin was isolated from the root of Peucedanum pareruptorum and the structure were established as 3’(R)-isobutyryloxy-4’(R)-acetoxy- 3’,4’-dihydroseselin (1) by spectroscopic methods. The absolute configuration was deduced by chemical correlations with known compounds.

■ Photoinduced Electron Transfer Reactions in Heterocyclic Chemistry

Maurizio Fagnoni

*Department o f Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy

Abstract

In this work, the most significant reactions underwent by heterocyclic compounds under photoinduced electron transfer conditions have been reviewed, focusing the attention onto the possible applications of such reactions in organic synthesis and heterocycle functionalizations.