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A soil bacterium, Klebsiella oxytoca TNM3 was found to produce a polysaccharide named AZ9 that shows suppressive effects on IgE antibody response in mice. When mice were administered with 50 to approximately 100 mg/kg AZ9 subcutaneousely for 4 consecutive days after immunization with trinitrophenyl (TNP)-keyhole limpet hemocyanin, anti-TNP IgE production was significantly suppressed, while the level of anti-TNP IgM was affected marginally. In AZ9-administered mice, IL-4 secretion from splenic cells was reduced to approximately 30% of the untreated control. Thus, AZ9 suppression of IgE production may be due to attenuating effects on the Th2-type response. Although oral administration of AZ9 alone had no effects on IgE production, ovalbumin (OVA)-induced oral tolerance of anti-TNP IgE response to TNP-OVA was markedly augmented when a suboptimal dose of OVA was administered orally in combination with AZ9. Collectively, our data suggest that AZ9 has beneficial suppressive effects on IgE-dependent allergic responses.

Iodocyclization of silyl group‐substituted homopropargylic carbamates and amides proceeded via 6‐exo‐dig mode to afford 6‐vinylene‐4,5‐dihydro‐1,3‐oxazines in moderate to quantitative yields. This is the first report for silyl group‐solely directed iodocyclization of alkynes utilizing the β‐silyl effect. Under these mild reaction conditions, various functionalities such as secondary alcohol, acetal, urea, and sulfide were tolerated.

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