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Masahiko Yamaguchi

Publications and source records attributed to Masahiko Yamaguchi.

15 recordsLinked to original sources
PubMed2003

Equatorial preference in the C[bond]H activation of cycloalkanes: GaCl3-catalyzed aromatic alkylation reaction.

GaCl(3) catalyzes the aromatic alkylation of naphthalene or phenanthrene using cycloalkanes. The C[bond]C formation predominantly takes place at the least hindered positions of the substrates, and equatorial isomers regarding the cycloalkane moiety are generally obtained. The reaction of bicyclo[4.4.0]decane and naphthalene occurs at the 2-position of naphthalene and at the 2- or 3-carbons of the cycloalkane, and the products possess a trans configuration at the junctures and an equatorial configuration at the naphthyl groups. Notably, cis-bicyclo[4.4.0]decane turns out to be much more reactive than the trans isomer, and a turnover number "TON" up to 20 based on GaCl(3) is attained. 1,2-Dimethylcyclohexane reacts similarly, and the cis isomer is more reactive than the trans isomer. Monoalkylcycloalkanes react at the secondary carbons provided that the alkyl group is smaller than tert-butyl. Adamantanes react at the tertiary 1-position. The alkylation reaction is considered to involve the C[bond]H activation of cycloalkanes with GaCl(3) at the tertiary center followed by the migration of carbocations and electrophilic aromatic substitution yielding thermodynamically stable products. The stereochemistry of the reaction reveals that GaCl(3) activates the equatorial tertiary C[bond]H rather than the axial tertiary C[bond]H.

Journal Article↗
PubMed2003

[3+3]Cycloalkyne dimers linked by an azo group: a stable cis-azo compound forms polymeric aggregates by nonplanar pi-pi interactions.

We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]cycloalkyne amine derivative, and the stereochemistry was determined by UV-vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene structure isomerizes readily.

Journal Article↗
PubMed2003

Rhodium-catalyzed disulfide exchange reaction.

A system of RhH(PPh3)4, trifluoromethanesulfonic acid, and (p-tol)3P catalyzes the disulfide exchange reaction. Treatment of two symmetrical dialkyl disulfides with the catalyst provides an equilibrium mixture of three disulfides within 15 min in refluxing acetone. The catalyst is active after reaching the equilibrium, and addition of a disulfide to the mixture changes the ratio of the products. The use of 4 mol equiv excess of one of the disulfides provides the unsymmetrical disulfide in a yield exceeding 80%. Disulfide-containing peptides also undergo an exchange reaction. The reactions of diaryl disulfides and dialkyl disulfides are even faster, and reach equilibrium within 5 min at room temperature in the presence of the rhodium complex and 1,2-bis(diphenylphosphino)ethane (dppe). This exchange reaction is considerably affected by the substituents on the disulfides. Treatment of diphenyl disulfide, di(p-tolyl) disulfide, and bis(sec-butyl) disulfide yields phenyl p-tolyl disulfide at room temperature with unchanged bis(sec-butyl) disulfide; random disproportionation occurs at reflux. The rhodium catalysis can be used for the exchange reaction of disulfides and diselenides giving selenosulfides as well as disulfides and ditellurides giving tellurinosulfides.

Catalysis↗
PubMed2003

Insulin gene transfer with adenovirus vector via the spleen safely and effectively improves posthepatectomized conditions in diabetic rats.

BACKGROUND: We examined administration methods of adenovirus vector carrying human insulin gene (AxCAIns), which could safely and effectively enhance liver regeneration in diabetic rats after hepatectomy. METHODS: Male Wistar rats were made diabetic with streptozotocin and subjected to 70% partial hepatectomy. AxCAIns was administrated into the spleen, the portal vein, the peritoneal cavity, or the femoral muscle. Liver regeneration and damage, and nutritional conditions were compared among the groups which were different in the administration methods of AxCAIns. RESULTS: Intrasplenic administration of AxCAIns enhanced liver regeneration, improving nutritional conditions without liver damage. In contrast, intraportal administration enhanced liver regeneration but caused hypoglycemia with liver damage. Neither intraperitoneal nor intramuscular administration produced detectable serum levels of human c-peptide, and did not enhance liver regeneration. CONCLUSIONS: In conclusion, data showed that intrasplenic administration of AxCAIns, rather than other methods, effectively enhanced liver regeneration without liver damage and improved nutritional conditions after hepatectomy in diabetic rats. It is suggested that insulin gene transfer with AxCAIns via the spleen may safely and effectively improve posthepatectomized conditions in inslinopenic patients.

Adenoviridae↗
PubMed2003

Magnetoencephalographic study of cortical activity evoked by electrogustatory stimuli.

Electrogustometry is a convenient method to examine taste acuity in clinical situations. Some basic properties of neural activity in the cerebral cortex in response to electrogustatory stimulation were revealed by measuring magnetoencephalography (MEG) signals with a whole-cortex-type system in response to varying intensities of anodal DC currents focally applied to the tongue surface in human subjects. Independent component analysis was used to eliminate stimulus artifacts in MEG signals. Electrogustatory stimulation with intensities of induced electric taste evoked responses bilaterally, mainly in the opercular-insular cortex with a mean onset latency of approximately 350 ms, while subthreshold electrogustatory stimulation induced modest responses in the cortex. Stronger stimulation induced a tingling sensation and elicited large transient responses in both the opercular-insular and somatic sensory cortices. This is the first description of the basic properties of human MEG responses to electrogustatory stimulation.

Adult↗
PubMed2003

Synchronous colorectal carcinoma: clinico-pathological features and prognosis.

OBJECTIVE: The present study was undertaken to clarify the clinical and pathological features of synchronous colorectal carcinomas, to compare prognosis between cases with synchronous carcinomas and those with single carcinomas and to explore prognostic factors of synchronous carcinomas. PATIENTS AND METHODS: Among 876 surgically resected primary colorectal carcinomas, 42 cases (4.8%) with synchronous carcinomas were identified. Clinical characteristics, routine pathological findings according to the TNM classification and postoperative survival were compared between synchronous cases and single cases. Prognostic factors of synchronous cases were explored using the proportional hazard model. RESULTS: The index lesions of synchronous cases did not differ from single lesions in age, size, differentiation, location, pT value, pN value, pathological stage, morphology or lymphatic invasion. However, the male:female ratio was higher and distant metastasis was more frequent in synchronous cases than in single cases. Although postoperative survival of synchronous cases was shorter than that of single cases, they were similar in the multivariate proportional hazard model including pathological stage and curability as co-factors. Only pathological stage and curability of the index lesion were significant co-factors of postoperative survival of synchronous cases. CONCLUSION: Synchronous carcinomas and single carcinomas were similar in clinical characteristics and routine pathological findings. The prognosis of synchronous cases and that of single cases did not differ if the pathological stages were identical and the resections were curative.

Adult↗
PubMed2002

GaCl(3)-catalyzed ortho-ethynylation of phenols.

Phenols are ethynylated at the ortho position with silylated chloroethyne in the presence of a catalytic amount of GaCl3 and lithium phenoxide. The lithium salt is essential for the catalysis, and addition of 2,6-di(tert-butyl)-4-methylpyridine inhibits desilylation and hydration of the products. The reaction can be applied to various substituted phenols giving the ortho-ethynylated products in high yields, and the turnover numbers based on GaCl3 are between 8 and 10. The reaction mechanism involves addition of in situ formed phenoxygallium to the haloethyne followed by the elimination of GaCl3.

Journal Article↗
PubMed2002

One-step ethynylation of silyl enol ether with chlorosilylethyne.

[reaction: see text] In the presence of GaCl(3), silyl enol ethers are ethynylated at the alpha-carbon atom with chlorotrimethylsilylethyne. This reaction can provide alpha-ethynylated aryl ketones possessing acidic alpha-protons without isomerization to conjugated allenyl ketones.

Journal Article↗
PubMed2002

Hepatocellular carcinoma in a patient with acromegaly and high serum levels of insulin-like growth factor I: report of a case.

A 64-year-old woman with high serum levels of growth hormone, insulin-like growth factor-I (IGF-I), and alpha-fetoprotein resulting from partially treated acromegaly was found to have a tumor under the left diaphragm. The patient also had a history of type C viral hepatitis. Laparotomy revealed that the tumor was fixed to the diaphragm and connected to the liver and spleen. The tumor was excised with partial resection of the diaphragm, liver, and spleen, and a diagnosis of left-sided pedunculated hepatocellular carcinoma (HCC) was made. Further examination showed a higher level of IGF-I receptor mRNA in the tumor than in the normal liver parenchyma. We believe it is likely that the high serum levels of IGF-I may have played a role in the development of the pedunculated HCC in this patient.

Acromegaly↗
PubMed2002

Chiral recognition in the binding of helicenediamine to double strand DNA: interactions between low molecular weight helical compounds and a helical polymer.

Binding of a helicene, 5,8-bis(aminomethyl)-1,12-dimethylbenzo[c]phenanthrene, to calf thymus DNA was studied using UV, CD, and fluorescence spectroscopy as well as calorimetry. The enantiomeric helicenes strongly bound to the double strand DNA possessing the right-handed helical structure. In addition, chiral recognition was observed in the binding, where the (P)-helicene with the right-handed helicity formed more stable complex than the (M)-helicene with the left-handed helicity. The binding studies of the helicenes and natural nucleosides by 1H NMR spectroscopy also revealed the higher affinity to the (P)-helicene. Both monomeric and polymeric nucleic acids thus turned out to favor the (P)-helicity.

Calorimetry↗
PubMed2002

Budding (sprouting) as a useful prognostic marker in colorectal mucinous carcinoma.

PURPOSE: Budding (sprouting) along the invasive margin is reported to be associated with high malignant potential of colorectal carcinoma. We examined the prognostic significance of budding in colorectal mucinous carcinoma. PATIENTS AND METHODS: Surgically resected specimens from 31 patients with colorectal mucinous carcinoma were studied. The median postoperative follow-up was 27 months. The presence of budding was examined according to Morodomi's criteria using hematoxylin-eosin-stained sections. RESULTS: Budding was found in 18 lesions (58%). Budding was more frequently observed in lesions with venous invasion and lymph node metastasis than in those without (P = 0.04, P = 0.03, respectively). The incidence of budding was higher in lesions with distant metastasis than in those without (P < 0.03). Overall recurrence and peritoneal disseminated recurrence were significantly more frequent in patients with budding-positive lesions than in those with budding-negative lesions (P = 0.05, P = 0.04, respectively). The cumulative 5-year survival rate of curative resected cases was lower in patients with budding-positive lesions than in those with budding-negative lesions (25.0% versus 90.9%, P = 0.01, log-rank test). Moreover, both the univariate and multivariate proportional hazard models revealed that the presence of budding was the only significant co-factor of postoperative survival. CONCLUSION: Budding is a pathological marker suggesting high malignant potential and decreased postoperative survival in patients with colorectal mucinous carcinoma.

Adenocarcinoma, Mucinous↗
PubMed2002

[Assessing liver function by magnetic resonance imaging two-dimensional phase-shift flow measurement of portal venous blood flow after oral intake of glucose].

We have already reported that the ratio of portal venous flow 30 min after oral intake of glucose 75 g to that before intake (PVFR30), measured using pulsed-Doppler ultrasonography (US), correlated significantly with other indicators of liver function and that it could be used to estimate hepatic function before surgery, including liver resection. In this study, to assess the disadvantages of pulsed-Doppler ultrasonography, PVFR30 was measured using two-dimensional (2D) phase-shift (PS) magnetic resonance imaging (MRI). PVFR30 was measured in 17 patients and 7 volunteers: 13 with liver cirrhosis (LC) and 11 without LC (non-LC). Portal venous flow could be measured in all patients without any disturbance of intestinal gas or patient fat, or the high degree of technical skill that Doppler US requires. PVFR30 was significantly lower in the LC group than in the non-LC group. In addition, it correlated significantly with other indicators of liver function, including the indocyanine green clearance test, prothrombin time, hepaplastin test, and cholinesterase activity. These results suggest that PVFR30 measured by 2D PS MRI can be used to estimate liver function, and that this MRI method can be performed more easily than pulsed-Doppler US.

Administration, Oral↗
PubMed1998

Ortho-Vinylation Reaction of Phenols with Ethyne.

Phenols were vinylated at the ortho-position with ethyne in the presence of SnCl(4)-Bu(3)N reagent. The reaction was applicable to phenols possessing either electron-donating or electron-withdrawing groups. 2,6-Divinylphenols were synthesized under modified conditions. A reaction mechanism involving carbostannylation of alkynyltin and phenoxytin was discussed.

Journal Article↗
PubMedDate not supplied

Prediction of pancreatic fistula by amylase levels of drainage fluid on the first day after pancreatectomy.

BACKGROUND/AIMS: We investigated whether it would be useful to monitor amylase levels of drainage fluid after pancreatic surgery for prediction of pancreatic fistula. METHODOLOGY: Twenty-six cases in which amylase levels of drainage fluid were determined after pancreatic surgery, were divided into 14 cases who did not develop pancreatic fistula and 12 cases who developed pancreatic fistula. Changes in amylase levels of sera and urine as well as drainage fluid were monitored. RESULTS: Amylase levels of drainage fluid were significantly higher in cases with pancreatic fistula than in cases without pancreatic fistula on the first postoperative day, but those levels in both groups decreased until the 7th postoperative day without significant difference. However, those levels in cases with pancreatic fistula significantly increased from the 9th postoperative day whereas the levels in cases without pancreatic fistula further decreased. There was no significant difference in amylase levels of sera or urine. CONCLUSIONS: Amylase levels of drainage fluid on the first postoperative day may be useful to predict development of pancreatic fistula and to plan appropriate management.

Aged↗