caa a22 4500 469128143 CHVBK 20180323133156.0 cr unu---uuuuu 170328e19921101xx s 000 0 eng 10.1007/BF01809370 doi (NATIONALLICENCE)springer-10.1007/BF01809370 Basiuk Vladimir Institute of Surface Chemistry, the Ukrainian Academy of Sciences, Prospekt Nauki 31, 252650, Kiev, the Ukraine aut Condensation of vaporous amino acids in the presence of silica. Formation of bi- and tricyclic amidines [Elektronische Daten] [Vladimir Basiuk] Amino acids (alanine, valine, norvaline, leucine, and 2-aminoisobutyric acid) were subjected to repeated (5-9 times) sublimation in the presence of silica at temperature of 220-240 °C. The major amino acid condensation products were diketopiperazines (DKPs) in yields of 27-89%. Mixtures of by-products have been isolated from the DKPs by means of chloroform extraction. On the basis of fast atom bombardment mass spectrometric studies of the mixtures it is proposed that under these conditions further dehydration proceeds resulting in bicyclic (BCA) and tricyclic (TCA) amidine derivatives of DKPs; the BCA formation has been confirmed by means of IR and1H NMR spectroscopy in the case of 2-aminoisobutyric acid. During the sublimation, thermal destruction of the cyclic products was also observed accompanied by the cycle degradation and cleavage of alkyl substituents. The BCAs and TCAs are considered as possible sources of linear di- and tripeptides. Kluwer Academic Publishers, 1992 Origins of life and evolution of the biosphere Kluwer Academic Publishers 22/6(1992-11-01), 333-348 0169-6149 22:6<333 1992 22 11084 https://doi.org/10.1007/BF01809370 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF01809370 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Basiuk Vladimir Institute of Surface Chemistry, the Ukrainian Academy of Sciences, Prospekt Nauki 31, 252650, Kiev, the Ukraine aut NATIONALLICENCE 773 0- Origins of life and evolution of the biosphere Kluwer Academic Publishers 22/6(1992-11-01), 333-348 0169-6149 22:6<333 1992 22 11084 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer