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Shinichi Saito

Publications and source records attributed to Shinichi Saito.

8 recordsLinked to original sources
PubMed2002

Addition of heteroaromatics to alkylidenecyclopropanes catalyzed by palladium.

The reaction of heteroaromatics, such as furans, thiophenes, thiazoles, and pyrroles, with alkylidenecyclopropanes proceeded smoothly in the presence of palladium catalysts, producing the corresponding alpha-allylated products in good to high yields. For example, the reaction of 3-butylpentylidenecyclopropane (1a) with 2-methylfuran (2a), ethyl 2-thiophenecarboxylate (4a), 2-isobutylthiazole (6a), and 1-methylpyrrole (11b) gave the alpha-allylated products in 70%, 66%, 77%, and 30% yield, respectively. The reaction proceeded predominantly through distal bond cleavage. The order of reactivity of heteroaromatics toward 1a is as follows: furan > thiophene approximately thiazole (5-position) > thiazole (2-position) approximately pyrrole. This methodology provides a means for introducing an allylic group to various kinds of heteroaromatics under mild conditions.

Journal Article↗
PubMed2002

Synthesis of phthalides and 3,4-dihydroisocoumarins using the palladium-catalyzed intramolecular benzannulation strategy.

A novel method for the synthesis of phthalides and 3,4-dihydroisocoumarins via the palladium-catalyzed intramolecular benzannulation of bis-enyne and enyne-diyne systems is described. Various kinds of substituted phthalides 9 and 17 and 3,4-dihydroisocoumarins 19 were synthesized from 8, 16, and 18, respectively, in moderate to excellent yields. The benzannulation reaction proceeded chemoselectively to give the corresponding fused ring compounds A without the formation of the regioisomeric products B (eq 6). Furthermore, this methodology was applied to the synthesis of biologically active 3-n-butylphthalide 23.

Journal Article↗
PubMed2002

[Effect of alfacalcidol on bone and calcium metabolism in elderly women].

Oral administration of active vitamin D3 can reduce the loss of bone mass and the incidence of fractures in patients with osteoporosis in Japan. We conducted a prospective study to confirm the effects of 1 alpha(OH)D3 (Alfacalcidol, Alfarol Chugai Tokyo) on bone and calcium metabolism in elderly women with osteoporosis. Enrolled in the present study were 16 elderly osteoporosis women aged 72.6 +/- 4.5 years to whom 1 microgram of 1 alpha(OH)D3 was administered daily. Fasting blood and urine were obtained at baseline, 1 week, 4 weeks, 12 weeks and 24 weeks after the treatment. Monitored parameters were vitamin D metabolites, intact-PTH, bone alkaline phosphatase (BAP), osteocalcin (OC), deoxypyridinoline (DPD) and pyridiuium crosslinked type I collagen telopeptides (CTx). Serum 1 alpha, 25(OH)2D and PTH levels were significantly increased (p < 0.01) and decreased (p < 0.05), respectively at 1 week after commencing administration. There was a significant decrease of DPD (p < 0.05) at 12 weeks after commencing administration compared to the baseline levels. Serum levels of BAP and OC were found elevated at 1 week, and decreased at 12 weeks. In conclusion, the present study clinically confirmed that 1 alpha(OH)D3 stimulates bone formation in vitro. Long-term administration of 1 alpha(OH)D3 indirectly suppressed bone resorption through the suppression of parathyroid function in the elderly.

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PubMed2001

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Journal Article↗
PubMed1996

Superacid-Catalyzed Reaction of Substituted Benzaldehydes with Benzene.

Benzaldehydes bearing an electron-withdrawing group reacted with 2 equiv of benzene in the presence of a superacid, trifluoromethanesulfonic acid, to give substituted triphenylmethane in good yields. On the other hand, benzaldehydes bearing an electron-donating or a neutral group reacted under the similar conditions to give unsubstituted diphenylmethane and triphenylmethanol, together with substituted benzene. We propose a new mechanism of this reaction, which involves transalkylation as the key step.

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