Dehydrochlorination of D-glucosamine (2-amino-2-deoxy-D-glucose) hydrochloride with an anion exchange resin made its DNA breaking activity in plasmid pBR322 much higher, especially in the presence of Cu2+. The sample of anion exchanger-treated D-glucosamine hydrochloride, i.e., HCL-free D-glucosamine sample, showed an absorption maximum at 274 nm on the UV absorption spectrum in water as seen in the case of fructosazine [2,5-bis(D-arabino-tetrahydroxybutyl)pyrazine] one of the dimers of D-glucosamine. On a positive-ion fast atom bombardment (FAB) mass spectrum, the sample showed an ion peak at m/z 323 as a base peak, corresponding to dihydrofructosazine [2,5-bis(D-arabino-tetrahydroxybutyl) dihydropyrazine], which was a precursor of fructosazine, as well as those of D-glucosamine itself (m/z 180) and fructosazine (m/z 321). The DNA strand breaking activity of HCL-free D-glucosamine sample was directly proportional to the peak intensity of m/z 323 ion, while the DNA breaking activity of fructosazine was much weaker than that of HCL-free D-glucosamine sample. 2,5-Dihydro-3,6-dimethylprazine and 2,3-dihydro-5,6-dimethylpyrazine having a dihydropyrazine skeleton the same as dihydrofructosazine showed the same extent of DNA strand breaking activity as did the HCL-free D-glucosamine sample. These results indicated that dihydrofructosazine produced during the dehydrochlorination is closely involved in the DNA breaking activity of HCL-free D-glucosamine sample.

A novel resin glycoside, merremin (1), has been isolated from the root of Merremia hungaiensis (Convolvulaceae). The structure has been determined to be an ester-type dimer of tuguajalapin X (2) on the basis of chemical and spectral data.

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The fragmentation of the sodium adduct ions for tert-butoxycarbonyl-L-prolyl-L-proline ethyl ester (Boc-L-Pro-L-Pro-OEt) was compared with that for Boc-D-Pro-L-Pro-OEt in positive-ion electrospray ionization (ESI) mass spectrometry. In the collision-induced dissociation (CID) mass spectra of the [M + Na](+) ions, the abundance of the [M + Na - C(CH(3))(3) + H](+) ion, which is due to the loss of a tert-butyl group from the [M + Na](+) ion for Boc-D-Pro-L-Pro-OEt, was about eight times higher than that for Boc-L-Pro-L-Pro-OEt. In addition, in the CID spectra of the sodium adduct fragment ion ([M + Na - Boc + H](+)), the abundance of the [M + Na - Boc - prolylresidue + H](+) ion, which is due to the loss of prolyl residue from the [M + Na - Boc + H](+) ion for Boc-L-Pro-L-Pro-OEt, was about five times higher than that for Boc-D-Pro-L-Pro-OEt. These results indicate that Boc-L-Pro-L-Pro-OEt was distinguished from Boc-D-Pro-L-Pro-OEt by the CID mass spectra of the sodium adduct ions in ESI mass spectrometry. The optimized geometries of the [M + Na](+) and the [M + Na - Boc + H](+) ions calculated by ab initio molecular orbital calculations suggest that the chiral recognition of these diastereomers was due to the difference of the orientation of a sodium ion to the oxygen and nitrogen atoms in dipeptide derivatives, and to the difference of the total energies between them.

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