We have found that N-acetylneuraminic acid (NANA) consumes toxic hydrogen peroxide (H 2 O 2 ) under physiological conditions. Close investigation of this ¢nding revealed that NANA was oxidized by an equimolar amount of H 2 O 2 to provide its decarboxylated product, 4-(acetylamino)-2,4-dideoxy-D-glycero-D-galacto-octonic acid (ADOA). To date, there have been little data on this reaction, and its physiological signi¢cance has not been discussed. Examining the detoxi¢cation of H 2 O 2 in cultured cells with NANA, we were able to con¢rm that the cell death caused by H 2 O 2 was suppressed by NANA in a dose-dependent manner. These results revealed a novel role for NANA as a reactive oxygen scavenger. It is known that terminal NANA residues are removed by neuraminidase and that free NANA molecules are recycled or degraded by enzymes. We propose that released monomeric NANA is the potent defense molecule against oxidative damage.

The stereoselective synthesis of ketoside‐type analogues of trehalose is described. O‐Glycosidation of hept‐2‐ulopyranose with trimethylsilyl α‐pyranoside promoted by trimethylsilyl trifluoromethanesulfonate afforded α‐ketopyranosyl α‐aldopyranosides exclusively. α‐Ketopyranosyl β‐aldooyranosides and α‐ketopyranosyl α‐ketopyranosides were also synthesized in a similar manner. The benzyl protecting groups of the hydroxy moieties were removed by hydrogenolysis to afford fully deprotected trehalose analogues.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Unusual sugar dimers: The synthesis of 6,6′‐ether‐connected pyranoses by an acetalization–reduction procedure is described (see scheme). Structure–activity‐relationship studies of these novel carbohydrate dimers suggested that the natural product coyolosa, which has been shown to have a significant effect on fasting blood‐glucose levels, may have a different structure from the one previously reported.

No abstract

From 2001 to the summer of 2002, more than 800 cases of liver damage were reported in Japan among people taking Chinese diet aids. The Japanese Ministry of Health, Labor and Welfare has recently announced that N-nitrosofenfluramine was the hepatotoxic compound contained in the diet aids based on animal experiments performed by the National Institute of Health Sciences. Although N-nitrosofenfluramine is a derivative of fenfluramine, a previously used antiobesity drug, neither pharmacologic nor toxicologic properties have been reported for N-nitroso fenfluramine. It should be noted that N-nitrosofenfluramine has two optical isomers, although it is not yet known which isomer damages the liver and other organs. The Japanese Ministry of Health, Labor and Welfare has not commented on this point. Pursuing this question, 10 types of Chinese slimming aid samples including those obtained from patients with fulminating hepatitis were analyzed by NMR, GC/MS, and a newly established HPLC method using a chiral separation column. It was found that the N-nitrosofenfluramine in all of the toxic diet aids was the (S)-isomer form. No (R)-isomer was detected. These results strongly suggest that the nitroso-compound in the diets must be prepared from pharmacologically active (S)-fenfluramine (dexfenfluramine). Thus the pharmacologic and toxicologic properties of each isomer should be investigated.