Über die Stabilität der N‐Glykoside, insbesondere der Guanidin‐glykoside und der Nucleoside

Abstract

Die Stabilitat der N-Glykoside ist in hohem MaRe abhilngigvon der Substitution des N-Atoms. Einbeziehung des glykosidischen N-Atoms in ein Resonanzsystem, wie es insbesondere im folgenden an Guanidinsystemen gezeigt wird, erhoht die Stabilitat so stark, da8 weitgehende Resistenz ge'gen durch H-Ionen katalysierte Hydrolyse eintritt. Dies erkiart auch die relativ hohe Stabilitat der N-glykosidischen Bindung in den Ribo-und 2-Desoxyribo-nucleosiden.

Contribution to the mechanism of the acid-catalyzed hydrolysis of purine nucleosides

“…Journal of the American Chemical Society / 94:13 j June 28,1972 It can be seen that, as a result of the presence of the positive charge, the electron densities of all the possible protonation sites are considerably reduced. Consequently, the acid-base properties of 1 and 2 will be different from those of the free base.…”

“…Some authors have carried out kinetic measurements without proposing any mechanism,25-27 while others have discussed the mechanistic aspects of the problem in a more qualitative manner. 28 It has been proposed that the N9 protonated species is transformed into a charged Schiff base through sugar ring opening, which then generates hydrolytic products by water addition. The most fundamental studies on purine nucleosides are due to Garrett32 and to Zoltewitz and coworkers.…”

N-Glucosyl conjugates of chlorinated anilines: spontaneous formation and cleavage

“…The catalytic sequence of Figure 5 has previously been used to explain the greatly different acid sensitivity of structurally different IV-glucosides with different mesomeric or electronic structures (Simon and Palm, 1965; Paulsen and Pflughaupt, 1980;Winkler and Sandermann, 1989). For example, the stability of IV-ribosyl purine and pyrimidine bases (Micheel and Heesing, 1960) and the greatly increased acid sensitivity of the reduced redox cofactor NADH over its oxidized form, NAD+, can be explained.…”

“…The general rule derived from many individual studies is that acid stability of IV-glucosides increases in the following sequence of aglycons: aliphatic amine = amino acids and their esters < aromatic amines < acid amides = urea, and thiourea derivatives (Micheel and Heesing, 1960; Paulsen and Pflughaupt, 1980). Similar rules apply to pesticidal IV-glucosides.…”

Synthesis of 5-Substituted Pyrimidines1

“…The study of the chemistry and of the biological significance of pseudouridine has attracted the attention of many investigators. Particularly interesting is the fact that this nucleoside is found in soluble RNA, which is known to be an important factor in protein synthesis.2, 3 The isolation and structure elucidation of pseudouridine4,5 was followed by its synthesis in low yields.6 While this work was in progress, an improved procedure for the preparation of this compound was reported.7…”