Satoshi Ichikawa 교수

The first total synthesis of the nucleoside antibiotic herbicidin B (1b) was achieved, where a novel aldol-type C-glycosidation reaction promoted by samarium diiodide (SmI2) was used as a key step. Treatment of methyl 3,4-O-(1,1,3,3-tetraisopropyl-1,3-disiloxanediyl)-1-phenylthio-2-ulos-β-d-glucuronate (13) with SmI2 in THF regioselectively gave the corresponding 1-enolate, which was readily trapped with 1-β-d-xylosyladenine 5'-aldehyde derivative 7 to afford the product 19a,b as an anomeric mix

Abstract A type of edible sea brown algae, Hijikia fusiforme , contains a high concentration of inorganic arsenic. In July 2004, the British Food Standard Agency (FSA) advised people not to eat a type of seaweed called Hijiki because it contained high levels of arsenic. We examined the removal of inorganic arsenic compounds in H. fusiforme by performing a soaking procedure with pure water, and the excretion of arsenic contained in Hijiki was investigated in mice. The total arsenic was measured b

The continued emergence of drug-resistance to existing antibacterial agents represents a severe and ongoing public health concern, which demands the discovery of new antibiotics. However the number of novel classes of antibacterial drugs launched in the clinic has been remarkably slow since the 1960s, and it is urgent to develop novel antibacterial agents to fight against drug-resistant bacterial pathogens. Peptidoglycan is a component of the bacterial cell wall, which consists of a repeated N-a

The phototropin (phot)-dependent intracellular relocation of chloroplasts is a ubiquitous phenomenon in plants. We have previously revealed the involvement of a short cp-actin (chloroplast actin) filament-based mechanism in this movement. Here, the reorganization of cp-actin filaments during the avoidance movement of chloroplasts was analyzed in higher time resolution under blue GFP (green fluorescent protein) excitation light in an actin filament-visualized line of Arabidopsis thaliana. Under s

Carbacaprazamycins, which are chemically stable analogues of caprazamycins, were designed and synthesized. These analogues were active against drug-resistant bacterial pathogens such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci, and their activities were comparable to those of the parent caprazamycins. The effect of treatment with carbacaprazamycin on morphological changes in S. aureus indicated that the mode of action was completely different from those of

Nucleoside natural products possess a variety of interesting biological activities, including antibacterial, antiviral and antitumor properties, and are therefore expected to be potential candidates for developing drugs. Complex nucleoside natural products exhibiting antibacterial activity by specific inhibition of bacterial cell wall peptidoglycan biosynthesis are described. In addition to the class of antibacterial nucleoside natural products, the newest members of nucleoside natural products

A novel efficient method for the synthesis of 3‘-β-branched uridines starting from uridine was developed, in which a SmI2-promoted intramolecular Reformatsky-type reaction was effectively used. 5‘-O-(Bromoacetyl)-3‘-ketouridine derivatives 12, 26, and 27 were synthesized from uridine and were subjected to an intramolecular Reformatsky-type reaction. When 12, 26, and 27 were treated with 2.0 equiv of SmI2 in THF at −78 °C, intramolecular carbon−carbon bond formation at the 3‘-β-position proceeded

Simplification of caprazamycins, which are promising antibacterial nucleoside natural products, was conducted by scaffold-hopping of the structurally complex diazepanone moiety to the isoxazolidine scaffold. The designed isoxazolidine-containing uridine derivatives were synthesized by an intramolecular 1,3-dipolar cycloaddition of alkenyl nitrone as a key step. The lactone-fused isoxazolidine intermediate was easily converted to the target compounds by sequential introduction of key substituents

It is important to pursue function-oriented synthesis (FOS), a strategy for the design of less structurally complex targets with comparable or superior activity that can be made in a practical manner, because compared to synthetic drugs, many biologically relevant natural products possess large and complex chemical structures that may restrict chemical modifications in a structure-activity relationship study. In this account, we describe recent efforts to simplify complex nucleoside natural prod