Mitsunobu Kobayashi

Reaction of disilanes with acetylenes : I. Stereoselective addition of methoxymethyldisilanes to phenylacetylene catalyzed by group-VIII metal phosphine complexes

Abstract Addition reactions of methoxymethyldisilanes to phenylacetylene in the presence of various triphenylphosphine complexes of Ni, Rh, Pd and Pt were investigated. Palladium and platinum complexes, Pd(PPh3)4, PdCl2(PPh3)2 and Pt(PPh3)4 were found to be effective catalysts for the double silylation, giving adducts, cis-α,β-disilylated styrene derivatives selectively. It also was shown that hexamethyldisilane reacted with the acetylene. A possible mechanism for the stereoselective and regioselective double silylation is proposed. The cis-adducts isomerized to the corresponding trans isomers in the presence of disilane and a palladium complex catalyst.

Reaction of disilanes with acetylenes : II. Double silylation of 1-hexyne, trimethylsilylacetylene and acetylene with methoxymethyldisilanes catalyzed by tetrakis(triphenylphosphine)palladium

Abstract In the presence of a palladium(0) complex catalyst, methoxymethyldisilanes, (MeO) n Me 3-n SiSiMe 3-m (OMe) m ( m , n  1, 2), added to 1-hexyne, trimethylsilyl-acetylene and acetylene to give double silylation products, 1,2-bis(methoxy-methylsilyl)olefins, in varying yields.

Effects of a p38 mitogen-activated protein kinase inhibitor as an additive to university of wisconsin solution on reperfusion injury in liver transplantation.

BACKGROUND Activation of p38 mitogen-activated protein kinase (MAPK) plays an important role in the development of ischemia/reperfusion injury in nonhepatic organs, such as the heart. However, the role of p38 MAPK activation in the liver is unclear. We examined the effects of FR167653, a novel p38 MAPK inhibitor, as an additive to University of Wisconsin (UW) solution in rat liver transplantation. METHODS Rat orthotopic liver transplantation was performed after 30 hr of cold storage using UW solution with or without FR167653. Ten-day survival rates, serum alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels, liver tissue blood flow, histological findings, and activities of p38 MAPK and p46/p54 c-Jun N-terminal kinase (JNK) in liver grafts were evaluated. RESULTS The addition of FR167653 significantly increased animal survival rates. FR167653 significantly suppressed serum ALT and LDH levels and improved liver tissue blood flow after transplantation. FR167653 also ameliorated histological damage to the liver graft. Neither p38 MAPK nor p46/p54 JNKs was activated during cold storage, whereas both were markedly activated within 30 min of reperfusion and remained activated until 60 min after reperfusion. FR167653 inhibited the activation of p38 MAPK both 30 and 60 min after reperfusion, but it did not affect the activation of p46/p54 JNKs. CONCLUSIONS The addition of FR167653 to UW solution improved liver graft viability and animal survival rates associated with the inhibition of p38 MAPK activation. These results suggest that inhibiting the activation of p38 MAPK may attenuate ischemia/reperfusion injury in liver transplantation.

Preparation of dimethyltetramethoxydisilane from the disilane fraction

Abstract Reaction of sym-dimethyltetrachlorodisilane, obtained by chlorination with hydrogen chloride of the higher-boiling residue produced in the Direct Synthesis of methylchlorosilanes, with methyl orthoformate or methanol/methyl orthoformate gave rise to sym-dimethyltetramethoxydisilane.

FR167653 attenuates ischemia and reperfusion injury of the rat lung with suppressing p38 mitogen-activated protein kinase

BACKGROUND FR167653 is a potent suppressant of tumor necrosis factor (TNF)-alpha and interleukin-1 (IL-1) production, and was shown to attenuate ischemia and reperfusion (I/R) organ injury in our previous experiment. Because p38 mitogen-activated protein (MAP) kinase has been reported to regulate the production of TNF-alpha and IL-1, we examined the effects of FR167653 in the rat lung I/R model and determined the expression and activation of p38 MAP kinase. METHODS Experiment 1: After 1 hour of ischemia, p38 MAP kinase, phosphorylated p38 MAP kinase (active form), histologic changes of the lung, and serum levels of TNF-alpha and IL-1beta were examined. Experiment 2: After 2 hours of reperfusion, arterial oxygen content (PaO(2)) and saturation (SaO(2)), serum TNF-alpha and IL-1beta levels, and histologic changes in the lung were examined. Rats were divided into three groups in Experiment 1. In the control group, a saline solution was administered and, in the FR group, 0.1 mg/kg per hour of FR167653 was administered, intravenously throughout the experiment, beginning 30 minutes before ischemia. In the non-ischemic group, samples were taken soon after thoracotomy. The rats were divided into control and FR groups in Experiment 2. RESULTS Experiment 1: One hour of ischemia induced almost no changes in the lung or serum cytokine levels. Meanwhile, FR167653 markedly attenuated the expression of phosphorylated p38 MAP kinase. Experiment 2: SaO(2) and PaO(2) were improved, serum cytokines were lower, and lung damage was less extensive in the FR group than in the control group. CONCLUSION FR167653 attenuates I/R injury of the lung and this attenuation is associated with suppression of p38 MAP kinase activation.

Spontaneous isolated dissection of the superior mesenteric artery and aneurysm formation resulting from segmental arterial mediolysis: a case report

BackgroundSpontaneous isolated dissection of the superior mesenteric artery (SMA) can lead to bowel ischemia, aneurysm rupture, or even death. Studies have suggested that mechanical or hemodynamic stress on the vascular wall of the SMA may be a contributor, but its pathogenesis is unclear.Case presentationA 57-year-old Japanese man with a history of untreated hypertension and hyperuricemia was admitted to our hospital with the sudden onset of severe epigastric pain. Laboratory findings showed elevated white blood cell count and C-reactive protein, and contrast-enhanced computed tomography (CT) of the abdomen demonstrated arterial dissection with luminal stenosis and aneurysm formation at the distal portion of the SMA after the branching of the jejunal artery, and intravenous nicardipine was administered. The patient’s epigastric pain resolved spontaneously but recurred on day 6 of his hospital stay. Contrast-enhanced abdominal CT revealed an enlarged aneurysm with wall thinning. Because of the risk of aneurysm rupture, the decision was made to perform aneurysmectomy and bowel resection on day 6. Histologic examinations revealed two separate dissecting lesions: one latent and the other resulting in aneurysm formation. Both lesions showed characteristics of segmental arterial mediolysis (SAM) with lack of arterial media, absence of internal and external elastic laminae and intimal proliferation.ConclusionsHistologic findings in the present case suggest that mechanical or hemodynamic stress on the vascular wall and SAM-related vascular vulnerability may concomitantly contribute to the onset of isolated SMA dissection.

[Ventricular septal defect associated with pulmonary hypertension in monozygotic twins--a case report with surgical repair].

This is a report of two-year-old female monozygotic twins, both having a ventricular septal defect (VSD, Kirklin type II) and accompanying moderate pulmonary hypertension (PH). The two patients underwent a patch closure procedure to repair the VSD at the same time, and their postoperative courses were uneventful. Rubenstein and Weaver have reported the only case of surgical treatment for monozygotic twins having both VSD and PH. Our patients are the second such case of surgical treatment of VSD and PH in monozygotic twins.

Formation of a new silicon-containing ring system, 1,1,2,2,3,3-hexamethyl-4,5-diphenyl-1,2,3-trisilacyclopent-4-ene

Reaction of sym-dimethoxytetramethyldisilane with diphenylacetylene in the presence of NaOMe catalyst in tetrahydrofuran gave a new silicon-containing ring system, 1,1,2,2,3,3-hexamethyl-4,5-diphenyl-1,2,3-trisilacyclopet-4-ene.

Formation and reactions of functional silyl anions

Functionalized silyl anions such as methyldimethoxysilyl anion and methoxydimethylsilyl anion were first prepared in common solvents and allowed to react with organic halides giving rise to functional organosilicon compounds.

Simple and convenient method for preparing dodecamethylcyclohexasilane

Dodecamethylcyclohexasilane, (Me2Si)6, was conveniently prepared in good yield from sym-dimethoxy-tetramethyldisilane in the presence of NaOMe catalyst in tetrahydrofuran.