Neue ¹H‐NMR‐Analyse der diastereomeren Aloine

Abstract

Eine umfassende Analyse der 1H‐NMR Spektren der Aloine “A” und “B” ergibt keine signifikanten Unterschiede in den chemischen Verschiebungen und Kopplungskonstanten zwischen beiden Diastereomeren des 10‐Glucosylanthrontyps. Lediglich die Signale der 2′‐Hydroxylprotonen sind leicht zu unterscheiden. Die Signale der anomeren Protonen erscheinen im gleichen Bereich wie die anderen Ringprotonen des Zuckers und konnten nur durch Anwendung der NMR Doppelresonanztechnik identifiziert werden. Die zweifelsfreie Zuordnung ermöglicht eine einfache spektroskopische Bestimmung der β‐Konfiguration der Glucosylreste in beiden Aloinen.

Novel Anthrone-Anthraquinone Dimers from Aloe elgonica

“…The spectrum obtained for elgonica-dimer B was similar to that for elgonica-dimer A except in the anthrone moiety where appreciable variations were observed (Table 1). These differences, which can only be attributed to a different arrangement of substituents around C-10, were much larger than those noted in the two forms of barbaloin (7). They can most probably be attributed to the 'shielding cone' (8) which occurs around the anthraquinone component of the dimer which, in elgonica-dimers A and B, affects different parts of the anthrone unit.…”

Quality control of Aloe vera (Aloe barbadensis) and Aloe ferox using band-selective quantitative heteronuclear single quantum correlation spectroscopy (bs-qHSQC)

“…Regarding the stereochemistry of aloin A and B, three studies were conducted in the 1980s, where nearly identical proton NMR spectra were reported (with the only different shift value at the 2'-OH), which is why the configurations were established using X-ray crystallography [22][23][24]. However, in a later study the absolute configurations were proven by two-dimensional NMR experiments and by means of circular dichroism [25].…”