Search results for: Masazumi Ikeda

Items from 1 to 18 out of 18 results

article

Successful treatment of severe intra‐amniotic inflammation and cervical insufficiency with continuous transabdominal amnioinfusion and cerclage: A case report

Masazumi Ikeda, Takeshi Ono, Keisuke Tsumura, Fumio Yamasaki, more

Journal of Obstetrics and Gynaecology Research > 46 > 10 > 2142 - 2146

Severe intra‐amniotic inflammation, even with a negative bacterial culture, can lead to premature labor. We report a 43‐year‐old multiparous woman with severe intra‐amniotic inflammation and cervical insufficiency at 23 weeks and 5 days of gestation. Continuous transabdominal amnioinfusion was started 2 days after the diagnosis. The amniotic fluid interleukin‐6 level normalized after 2 days of treatment...

article

Continuous amnioinfusion for treatment of mid‐trimester preterm premature rupture of membranes with oligoamnios

Takeshi Ono, Keisuke Tsumura, Izumi Kawasaki, Masazumi Ikeda, more

Journal of Obstetrics and Gynaecology Research > 46 > 1 > 79 - 86

Aim Given the scarcity of relevant reports, this study aimed to elucidate whether pregnancy can be prolonged by maintaining the amniotic fluid volume with continuous transabdominal amnioinfusion (TA) for patients with mid‐trimester preterm premature rupture of membranes (PPROM) and oligoamnios. Methods We retrospectively examined patients who were managed during hospitalization at our department...

article

Remarkable rate acceleration of the solvent-free Baeyer-Villiger reaction on the surface of NaHCO ₃ crystals for sterically congested cyclic and acyclic ketones

Takayuki Yakura, Tomoko Kitano, Masazumi Ikeda, Jun'ichi Uenishi

Tetrahedron Letters > 2002 > 43 > 39 > 6925 - 6927

Baeyer-Villiger reactions of sterically crowded cyclic and acyclic ketones are remarkably accelerated by carrying out the reactions under solvent-free conditions in the presence of powdered NaHCO ₃ . The corresponding lactones and esters have been obtained in excellent yields.

article

Stereoselective Conjugate Addition of Alkyl Groups to (S)-4-(tert-Butyldimethylsilyloxy)-2-cyclopentenone Derivatives

Takayuki Yakura, Kenji Tanaka, Tomoko Kitano, Jun'ichi Uenishi, more

Tetrahedron > 2000 > 56 > 39 > 7715-7721

Reaction of (S)-2-benzenesulfonyl-4-(tert-butyldimethylsilyloxy)-2-cyclopentenone (2) and a 2-methoxycarbonyl congener (3) with R₂CuLi or RMgBr-CuI stereoselectively gave (2S,3R,4S)-3-alkyl-2-benzenesulfonyl-4-(tert-butyldimethylsilyloxy)cyclopentanone (4) and its (2S,3S,4S)-2-methoxycarbonyl derivative (5) as a major diastereoisomer. On the other hand, reaction with R₃Al in toluene exclusively gave...

article

Synthesis of heterocycles using the intramolecular heck reaction involving a 'formal' anti-elimination process

Masazumi Ikeda, Serry A. A. El Bialy, Takayuki Yakura

Heterocycles > 1999 > 51 > 8 > 1957-1970

This review summarizes the synthetic studies of a variety of heterocycles using the intramolecular Heck reaction which involves a formal anti-elimination of HPdX.

article

Chemo- and Stereoselective Dirhodium(II)-Catalyzed C-H Insertion Reaction of 5,6-Dioxygenated 2-Diazo-3-oxohexanoates: Synthesis of An Optically Active Highly Functionalized Cyclopentane

Takayuki Yakura, Akiharu Ueki, Tsuyoshi Kitamura, Kenji Tanaka, more

Tetrahedron > 1999 > 55 > 24 > 7461-7470

Methyl (S)-α-diazo-2,2-dimethyl-β-oxo-1,3-dioxolane-2-butanoate (4), upon treatment with dirhodium(II) tetraacetate in refluxing dichloromethane, gave methyl (1S,5S)-2,2-dimethyl-7-oxo-3,8-dioxabicyclo[3.2.1]octane-1-carboxylate (5) via oxonium ylide formation/1,2-shift. On the other hand, a similar treatment of methyl (S)-5,6-bis[tert-butyldimethylsilyl(TBDMS)oxy]-2-diazo-3-oxohexanoate (9a) afforded...

article

Stereoselective Radical Cascade Approach to Benzo[a]quinolizidines

Hiroyuki Ishibashi, Masatake Inomata, Masashi Ohba, Masazumi Ikeda

Tetrahedron Letters > 1999 > 40 > 6 > 1149-1152

The treatment of enamide 15, having an (E)-4-ethoxycarbonyl-3-butenyl group on the nitrogen atom, with Bu ₃ SnH-AIBN in boiling benzene, afforded a 1.2:1 mixture of two benzo[a]quinolizidine stereoisomers 16 and 17 as a result of cascade radical cyclization. A similar treatment of the (Z)-4-ethoxycarbonyl-3-butenyl congener 19 gave 16 and 17 in a ratio of 3.4:1. The high stereoselectivity...

article

5-Endo-trig radical cyclization of 2-chloro- and 2,2-bis(phenylthio)-N-methyl-N-(6-phenylcyclohex-1-en-1-yl)acetamides

Masazumi Ikeda, Shinji Ohtani, Michiyo Okada, Emi Minakuchi, more

Heterocycles > 1998 > 47 > 1 > 181-186

Treatment of 2-chloro-N-methyl-N-(6-phenylcyclohex-1-en-1-yl)-acetamide (4a) with Bu ₃ SnH in the presence of AIBN gave a 2.5:1 mixture of cis- and trans-fused N-methyl-7-phenyloctahydroindol-2-ones (5a and 5b) (13% combined yield), N-methyl-N-(2-phenylcyclohex-1-en-1-yl)acetamide (6) (19%), N-methyl-N-(6-phenylcyclohex-1-en-1-yl)acetamide (7) (13%), and N-(cyclohex-1-en-1-yl)-N-methyl-2-phenylacetamide...

article

Synthesis of a Chiral 1β-Methylcarbapenem Key Intermediate Using Radical Cyclization of N-Vinylic α-Bromo Amides

Hiroyuki Ishibashi, Chisato Kameoka, Kazuya Kodama, Hirotaka Kawanami, more

Tetrahedron > 1997 > 53 > 28 > 9611-9622

The chiral 1β-methylcarbapenem key intermediate 5 was synthesized by using radical cyclization of N-vinylic α-bromo amide 18 as a key step.

article

Triethylborane-mediated atom transfer cyclization of N-allylic α-iodoacetamides: a convenient synthesis of β-iodomethyl-γ-lactams

Masazumi Ikeda, Hirotaka Teranishi, Noriko Iwamura, Hiroyuki Ishibashi

Heterocycles > 1997 > 45 > 5 > 863-866

In the presence of triethylborane, N-allylic α-iodoacetamides underwent atom transfer cyclization to give β-iodomethyl-γ-lactams in high yields.

article

New entry to 1,4,5,6-tetrahydro-2H-indol-2-ones using a cationic 5-endo-trigonal cyclization onto enamides

Hiroyuki Ishibashi, Masahiro Higuchi, Hiromi Masuko, Kazuya Kodama, more

Heterocycles > 1997 > 46 > 37-40

A new method for the synthesis of 1,4,5,6-tetrahydro-2H-indol-2-ones by means of 5-endo-trigonal cyclization of α-thiocarbocations generated from sulfoxide (12) and α-chlorosulfide (17) is described. The sulfoxide (12), upon heating with TsOH, gave 14, which eliminated benzenethiol to give tetrahydroindolone (15). By contrast, the chlorosulfide (17), upon treatment with TiCl ₄ , gave the...

article

Synthesis of tetrahydro-1-benzazocin-2-(1h)-ones using 8-endo-trig radical cyclization of 2,2-bis-(phenylthio)-N-[o-(prop-2-enyl)-phenyl]acetamides

Masazumi Ikeda, Ken-ichi Obata, Jun-ichiro Oka, Hiroyuki Ishibashi, more

Heterocycles > 1997 > 44 > 1 > 203-212

The effects of N-substituents upon the 8-endo-trig radical cyclization of 2,2-bis(phenylthio)-N-[o-(prop-2-enyl)phenyl]acetamides (4) were examined. TheN -(p-methoxybenzyl) (4a) and N-tosyl derivatives (4b), when treated with tributyltin hydride in the presence of a small amount of azoisobutyronitrile, gave regioselectively the corresponding 3,4,5,6-tetrahydro-3-phenylthio-1-benzazocin-2(1H)-ones...

article

Synthesis of 4-Oxo-2-azetidineacetic Acids by Means of Radical Cyclization of N-Vinylic α-Bromo Amides

Hiroyuki Ishibashi, Kazuya Kodama, Chisato Kameoka, Hirotaka Kawanami, more

Tetrahedron > 1996 > 52 > 44 > 13867- 13880

Bu ₃ SnH-mediated radical cyclization of α-bromo amide 8, bearing phenyl and phenylthio substituents at the terminus of the N-vinylic bond, proceeded in a 4-exo-trig manner to give β-lactam 9. Ruthenium tetroxide oxidation of the phenyl group incorporated into the product 9 provided a new synthesis of 4-oxo-2-azetidineacetic acid 13, a usuful intermediate for (±)-PS-5. Chiral 4-oxo-2-azetidineacetic...

article

Radical Cyclization of Chiral N-(1-Cycloalken-1-yl)-α-haloacetamides: Synthesis of Optically Active Bicyclic Pyrrolidinones

Hiroyuki Ishibashi, Yumi Fuke, Takashi Yamashita, Masazumi Ikeda

Tetrahedron: Asymmetry > 1996 > 7 > 9 > 2531-2538

Asymmetric induction in the 5-endo-trig radical cyclization of N-(1-cycloalken-1-yl)-α-haloacetamides has been examined. α-Iodo amide 7 bearing an (S)-1-(1-naphthyl)ethyl group on the nitrogen afforded a 92:8 mixture of bicyclic lactams 9a, b, which was transformed into (3aR,7aR)-octahydroindol-2-one 10a in 77% ee. α-Bromo amide 11 bearing anN -(R)-1-phenethyl group provided a 61:39 mixture of 13a,...

article

Asymmetric radical cyclization leading to β-lactams: Stereoselective synthesis of chiral key intermediates for carbapenem antibiotics PS-5 and thienamycin

Hiroyuki Ishibashi, Chisato Kameoka, Kazuya Kodama, Masazumi Ikeda

Tetrahedron > 1996 > 52 > 2 > 489-502

A stereoselective synthesis of β-lactams by 4-exo-trig radical cyclizations of N-[2,2-bis(phenylthio)ethenyl]-α-bromo amides bearing a chiral inductor on the nitrogen atom has been examined. Bromide 8, upon treatment with Bu ₃ SnH in the presence of AIBN in boiling benzene, gave a mixture of (4S)-2-azetidinone 12a and its (4R)-isomer 12b in a ratio of 71:29 and 69% combined yield. Similar...

article

Sulfur-directed 5-Exo selective aryl radical cyclization onto enamide: A simple route to chilenine

Hiroyuki Ishibashi, Hirotaka Kawanami, Hiroko Iriyama, Masazumi Ikeda

Tetrahedron Letters > 1995 > 36 > 37 > 6733-6734

Bu ₃ SnH-mediated aryl radical cyclization of the N-(o-bromoaroyl)enamine 5 took place in a 5-exo-trig manner exclusively to give isoindolone 7, which was transformed into the key intermediate 11 for the synthesis of isoindolobenzazepine alkaloid chilenine (2).

article

Uncatalyzed cationic olefin cyclizations of N-vinylic α-chloro-α-thioacetamides. Formation of β- and γ-lactams

Hiroyuki Ishibashi, Tohru Nakaharu, Masako Nishimura, Atsuko Nishikawa, more

Tetrahedron > 1995 > 51 > 10 > 2929-2938

N-Vinylic α-chloro-α-thioacetamides were found to cyclize without a catalyst in two different manners depending upon the nature of the substituents at the terminus of the N-vinylic bond. Thus, bis(phenylthio)-substituted enamides 8a-c cyclized in a 4-exo-trig manner to give 4-methylene-β-lactams 10a-c, whereas mono(phenylthio)-, monophenyl-, diphenyl-, and dialkyl-substituted congeners 23a,b, 28,...

article

Synthesis of a simple kainic acid analogue by means of carbamoylmethyl radical cyclization

Tatsunori Sato, Ken-ichiro Matsubayashi, Kazumi Yamamoto, Hiroko Ishikawa, more

Heterocycles > 1995 > 40 > 1 > 261-270

A new approach to (-)-(2S, 3R)-2-carboxy-3-pyrrolidineacetic acid (6) starting from d-serine is described. The key step is a radical cyclization oftert -butyl (S)-3-[2,2-dimethyl-N-[chloro(phenylthio)acetyl]oxazolidin-4-yl]-(E)-propeno ate (15b), which gave tert-butyl (6S, 7R, 7aS)-5,6,7,7a-tetrahydro-3,3-dimethyl-5-oxo-6-phenylthio-1H, 3H-pyrrolo[1,2-c]oxazol-7-ylacetate (16b) in a highly regio-...

Filter options

Publication date

Set your own date range

INFONA - science communication portal

Search results for: Masazumi Ikeda

Add recipient

Sending message cancelled

Are you sure you want to cancel sending this message?

Send message

Filter options

Publication date

Date range setting

Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.

Content availability

Keywords

Data set

Journal

Reporting an error / abuse

Sending the report failed

Accessibility options