Paper ionophoresis of amino compounds. Formation of carbamates, and related reaction

Abstract

Carbamates (N-carboxy derivatives) are formed when solutions of primary or secondary amino compounds in strong alkali are exposed on paper strips to carbon dioxide, and may be separated by paper ionophoresis and detected as additional, anionic components. The formation of mono-, di-, tricarbamates, and so on, from a polyamino compound occurs concurrently, and when an amino compound containing n reactive groups is submitted to paper ionophoresis in 0.lN sodium hydroxide at 18-20� after exposure to carbon dioxide, it affords n additional spots. Most primary and secondary amino groups in saturated compounds, and some aromatic amino groups, are reactive, but highly hindered amino groups are not. Some unreactive groups become reactive when the ionophoresis is conducted at 1-2�. The procedure is analytically useful, and may be used to gain information about the structure of amino compounds. The conditions favouring the formation of carbamates have been defined by paper ionophoresis. The primary reaction in the formation of carbamates is the addition of carbon dioxide to the amino nitrogen atom; carbamates are not formed directly from the carbonate ion. The rate of reaction with carbon dioxide and the stability of the carbamates may be correlated with the steric and electronic environment of the amino groups. Low temperature and high alkalinity are essential for the stability of carbamates in solution.�The "basic mercury carbamates" described by Neuberg and Kerb (Biochem. Z., 1912, 40, 498) do not seem to have the structure assigned by these authors. Dithiocarbamates obtained by reaction of amines with carbon disulphide in alkaline solution are easily identified by paper ionophoresis, but they cannot readily be formed on the paper strip. Attempts to prepare N-sulphinates by reaction of amino compounds with sulphur dioxide on paper strips have been unsuccessful.

Bicarbonate‐dependence of responses to ethylenediamine in the guinea‐pig isolated ileum: involvement of ethylenediamine‐monocarbamate

“…Furthermore, the present results show the ease with which EDAC is formed from EDA in the presence of carbon dioxide; indeed, EDAC can even be formed from EDA with atmospheric carbon dioxide (Frahn & Mills, 1964), which suggests that this conversion would probably occur in any experiments on EDA actions in the presence of bicarbonate buffer, either in vivo or in vitro. However, the bicarbonate ion itself may modify neuronal properties, possibly rendering neurones sensitive to EDA, since changes in neuronal behaviour, and GABA-receptor affinity, have been seen in the presence of bicarbonate-carbon dioxide buffer (Brown & Berman, 1970;Kurioka et al, 1981;Fukuda, 1984;).…”

“…However, responses to EDA promptly appeared if bicarbonate solution, as KBC previously gassed with carbon dioxide, was first added to the bath containing KPO or KHO. It was only necessary to add a (Jensen & Christensen, 1955;Frahn & Mills, 1964). Furthermore, the synthetic EDAC used here was prepared by the method of Katchalski et al (1951) Although the exact mechanism whereby EDAC exerts this GABA-releasing effect is at present unclear, there is the possibility that EDAC may counterexchange for endogenous GABA in neurones of the myenteric plexus.…”

“…Although all this may merely indicate that HCO3-ions are somehow necessary for these EDA actions, since bicarbonate directly influences the affinity of GABA receptors (Kurioka et al, 1981), it is also possible that EDA must, instead, first undergo conversion to some directly GABA-mimetic compound in the presence of the bicarbonate buffer of KBC, the most likely product being the monocarbamate (EDAC) that readily forms from EDA in the presence of carbon dioxide (Jensen & Christensen, 1955;Frahn & Mills, 1964). The latter possibility is strongly supported by the observation (Curtis & Malik, 1984) that EDAC, prepared in aqueous solution from EDA by treatment with carbon dioxide, is a GABA-mimetic with a potency and speed of action comparable with that of GABA itself, in contrast to the parent diamine which is less potent and slower acting on dorsal horn cells of the cat spinal cord.…”

X-Ray Structure of the Amidase Domain of AtzF, the Allophanate Hydrolase from the Cyanuric Acid-Mineralizing Multienzyme Complex

“…However, N-carboxycarbamate is highly unstable in an aqueous environment, decaying by spontaneous decarboxylation to form carbamate and carbon dioxide. As the stability of carbamates is known to be temperature and pH dependent (58), the pH of the AtzF-catalyzed reactions was raised to 9 and the temperature was reduced to 4°C. Despite the conditions favoring the accumulation of N-carboxycarbamate, we were unable to detect this product in reactions catalyzed by either full-length AtzF or AtzF 467 .…”

Isolation of Toxic Metabolites of Phomopsis leptostromiformis Responsible for Lupinosis

“…(iv) Paper electrophoresis Paper electrophoresis was conducted in an enclosed strip apparatus (Frahn and Mills 1964) using Whatman No.4 paper in strips 13·5 by 61 cm with 45 cm enclosed under pressure and cooled by the circulation of tap water at about 20°C through the coils of the cooling plate.…”