Nitrogen-containing carbohydrate derivatives. XIV. Configurational studies on amino-sugars using cuprammonium solutions.
A study has been made of the optical rotational shifts and conductance changes in cuprammonium solutions of eight isomeric amino-glycosides. The results are in agreement with the findings of Reeves for vicinal diol systems. Care must be taken in using small optical rotational shifts alone as evidence for the absence of complexing with a vic-amino-alcohol grouping. These techniques have been used to relate methyl 5-amino-1,3-O-benzylidene-5-deoxy-β-D-fructoside and -α-L-sorboside to their respective hydroxy-compounds.
Nitrogen-containing carbohydrate derivatives
An epimeric pair 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-D-talo-heptitol and 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-D-galacto-heptitol, was synthesized from D-mannose. The absolute configuration at C-2 was based on the rules relating the signs of the Cotton effect of the o.r.d. curves and the c.d. maxima to the configuration at C-2 of the carbohydrate C-nitro alcohols. This assignment was confirmed by chemical degradation of 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-D-talo-heptitol to D-serine. Another epimeric pair, 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-L-manno-heptitol and 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-L-gluco-heptitol, was synthesized, and the configurations at C-2, determined by optical methods, agreed with those established by chemical methods.
Identification of Dihydroxy Aromatic Compounds in a Low-Temperature Pyrolysis Coal Tar by Gas Chromatography−Mass Spectrometry (GC−MS) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS)
Dihydroxy aromatics in coal tar undergo rapid coupling reactions with each other and with some coal-derived species during coal pyrolysis and liquefaction. However, only limited information on the structure of dihydroxy aromatics is known. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography−mass spectrometry (GC−MS) were used to characterize the dihydroxy aromatics in a low-temperature pyrolyzed coal tar and its distillate and residue fractions. Negative-ion electrospray ionization (ESI) FT-ICR MS spectra of coal-tar-derived samples had low molecular masses and narrow mass ranges. Negative-ion ESI is extremely selective for the dihydroxy aromatics present in coal tar. The O2 class species had the highest ion intensity among the species in the negative-ion FT-ICR mass spectrum for each sample. Dihydroxy compounds with an aromatic core structure of benzene, indan, biphenyl (and/or acenaphthene), and naphthalene were identified in the distillate fract...