Biomimetic flavin-catalysed reactions for organic synthesis.

Using simple riboflavin related compounds as biomimetic catalysts, catalytic oxidation of various substrates with hydrogen peroxide or molecular oxygen can be performed selectively under mild conditions. The principle of these reactions is fundamental and will provide a wide scope for environmentally benign future practical methods.

Rhodium complex-catalyzed reaction of isonitriles with carbonyl compounds: catalytic synthesis of pyrroles.

[figure: see text] Low-valent rhodium complexes are efficient catalysts for the activation of alpha-C-H bond of isonitriles. Addition of isonitriles to carbonyl compounds proceeds under mild and neutral conditions to give the corresponding alpha,beta-unsaturated formamides. Catalytic synthesis of pyrroles can be performed by cyclocondensation of isonitriles with 1,3-dicarbonyl compounds.

Low-valent ruthenium and iridium hydride complexes as alternatives to Lewis acid and base catalysts.

The discovery of a new chemical reaction often leads to new applications and new chemical principles. Low-valent ruthenium and iridium hydride complexes are highly useful redox Lewis acid and base catalysts. Nitriles are activated by these catalysts and undergo reactions with either nucleophiles or electrophiles under neutral conditions. Hydration of nitriles, esterification of nitriles with alcohols, and amidation of nitriles with amines can be performed catalytically together with formation of ammonia. The catalytic reactions of pronucleophiles such as nitriles and carbonyl compounds with electrophiles such as alkenes, alkynes, carbonyl compounds, imines, and nitriles take place generally.

Differentiation of smooth muscle cells from undifferentiated cells of chicken gizzard occurs on the layer of fibroblast-like cells.

We examined the in vitro differentiation of smooth muscle cells from undifferentiated cells of embryonic chicken gizzard. We used the gizzard from 7-day-old embryos (Hamburger and Hamilton's stage 26-28) as a source of culture, since the expression of myosin is extremely low, and the gizzard consists of round cells, which are not stained by anti-smooth muscle myosin antiserum. When the dissections of the gizzard were cultured, they attached to the dish, and fibroblast-like cells migrated within 4 days after the culture. Then round cells migrated from the transplants over the layer of fibroblast-like cells. At 12-14 days after the culture, smooth muscle cells, which were ribbon-shaped and stained by anti-smooth muscle myosin antiserum, appeared in the layer of round cells. The dissected transplant itself was not stained by anti-smooth muscle myosin antiserum even after being cultured for 15 days. We concluded then that the smooth muscle cells were differentiated from the round cells, which spread on the layer of the fibroblast-like cells. We also observed the differentiation of smooth muscle cells when the cells separated from 7-day-old embryo cultured on the layer of cloned fibroblast cells. We suggest that the fibroblast-like cell may play an important role in the differentiation of smooth muscle cells.