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.
Circularidichroismus—VI : Tieftemperaturmessungen an nitrosteroiden☆
Zusammenfassung Die Abhangigkeit des Circulardichroismus einiger Mononitro-, gem-Halogennitro- und gem-Dinitro-steroide in Methylcyclohean-Isopentan (1:3)-Losung von der Temperatur lasst sich allein durch Annahme von Konformationsgleichgewichten erklaren, Solvatationseffekte scheinen keine grosse Rolle zu spielen. Das 7α-Chlor-7β-nitro-5α-cholestan zeigt als enzige der untersuchten Verbindungen eine Vorzeichenumkehr von Δemax beim Abkuhlen. Eine Kuvette zur Messung des Circulardichroismus bei Temperaturen bis zu −188° wird beschrieben.