Eiichi Kotani

The aryl–aryl coupling reaction of 1-naphthol with SnCl4 for 2,2′-binaphthol synthesis and its application to the biomimetic synthesis of binaphthoquinone isolated from Plumbagozeylanica

Abstract A simple method for the direct synthesis of 2,2′-binaphthols was developed, utilizing aryl–aryl coupling reaction via electron donor–acceptor complexes of 1-naphthols with SnCl 4 . Heating of the complex in a sealed tube afforded the corresponding o - o coupling product in excellent yield. This method was utilized for a biomimetic synthesis of the binaphthoquinone, 3,3′-biplumbagin, isolated from Plumbago zeylanica .

Total synthesis of the alkloids (±)-oxocrinine and (±)-oxomaritidine via anodic oxidation

(±)-Oxocrinine (5a) and (±)-oxomaritidine (5b) were synthesized by anodic oxidation of the trifluroacetyl derivatives of N-(4-methoxyphenethyl)-3,4-methylenedioxybenzylamine (3a) and N-(4-methoxyphenethyl)3,4-dimethoxybenzylamine (3b) followed by hydrolysis.

A new synthesis of the alkaloid (±)-colchicine

The alkaloid (±)-colchicine (1) was synthesized by a methylene transfer reaction from the spirodienone (3b), followed by acid catalysed rearrangement and dehydrogenation to give deacetamido-isocolchicine (7).

Involvement of testosterone in the induction of hepatic microsomal cytochrome P-450 2B1/2 (P-450 2B1/2) by 1-benzylimidazole in male and female rats: sex-differentiated induction of P-450 2B1/2 species.

We examined the effect of 1-benzylimidazole on the induction of cytochrome P-450 1A1/2 (P-450 1A1/2) and cytochrome P-450 2B1/2 (P-450 2B1/2) in normal, castrated, ovariectomized and hypophysectomized male rats, and in castrated rats treated with testosterone. 1-Benzylimidazole markedly increased P-450 content in male and female rats. Parallel to the dose-dependent increase in P-450 content, 1-benzylimidazole produced a significant increase in P-450 2B1/2 in male rats, but not in female rats. 1-Benzylimidazole failed to induce P-450 2B1/2 in castrated male and ovariectomized female rats. Treatment of castrated male rats with testosterone restored the induction of P-450 2B1/2 by 1-benzylimidazole. Treatment of ovariectomized female rats with 1-benzylimidazole or phenobarbital led to the increase in P-450 content, accompanying by the induction of P-450 2B1/2 by the latter treatment, but not the former. In hypophysectomized male rats, 1-benzylimidazole was able to induce P-450 2B1/2 in contrast to castrated male rats. Neonatal male and female rats responded well to the induction of P-450 2B1/2 by 1-benzylimidazole. The present findings suggest that P-450 2B1/2 induction by 1-benzylimidazole would be coupled with circulating testosterone regulated by hypophysis-testis axis. 1-Benzylimidazole produced sex-differentiated induction of P-450 2B1/2 in pubertal rats, but not in neonatal animals. The present findings would be provide information on a unique effect of 1-benzylimidazole on P-450 2B1/2 induction in rats.

SnCl4-mediated oxidative reaction for formation of binaphthoquinone and dinaphthofuran frameworks and its application to natural product synthesis

Abstract A simple method was developed for the direct synthesis of 2,2′-binaphthoquinones and dinaphtho[1,2-b;2′,1′-d]furans, utilizing an oxidative reaction via electron donor–acceptor complexes of 1-naphthols with SnCl4 in the absence or presence of dioxygen. As an application of this method to natural product synthesis, we describe a facile biomimetic synthesis of several binaphthoquinones, 3,3′-bijuglone, 3,3′-biplumbagin and elliptinone.

New reagent system containing CrO3 and syntheses of neo-lignans

Oxidations of 1-arylprop-1-enes by the new reagent systems, CrO3–HBF4–MeCN or CrO3–HCIO4–MeCN gave the 4-aryltetraiones (1a) and (1c), and the tetrahydrofuran (3) which are precursor molecules for aryltetrahydronaphthalene and tetrahydrofuran neo-lignans.