Über China‐Alkaloide. 9. Mitteilung. Über den Einfluss der Konfiguration auf die Basizität und über die relative Konfiguration an den Kohlenstoffatomen 8 und 9

Abstract

Auf Grund von experimentell bestimmten Dissoziationskonstanten des Stereoisomeren‐Paares: (−)‐Ephedrin, (+)‐Pseudo‐ephedrin und ihrer N‐Methyl‐Derivate, sowie von theoretischen Überlegungen wurde geschlossen, dass bei α‐Amino‐alkoholen vom Typus III bis VI die racemoide Form basischer ist als die mesoide, besonders wenn die Amino‐Gruppe tertiär ist.

The relationship of physico-chemical properties and structure to the differential antiplasmodial activity of the cinchona alkaloids

“…A value of 8.5 ± 0.15 (table 1) was found, with a slight increase in HQ and HQD due to the conversion of the electron-attracting vinyl group to an ethyl group. All the cinchona alkaloids in table 1 had very similar pK a2 values (4.25 ± 0.15) for the more weakly basic quinoline aromatic N. The only previous determinations [41] for the threo compounds EQ and EQD were carried out in 80% methyl-cellosolve / 20% water and showed both 9-epimers to have higher pK a values than Q and QD in the same solvent. Results obtained in water (Table 1) confirmed this finding and revealed a consistent ΔpK a1 of 1.1 units between the two solvent systems, and of 1pK a unit between the erythro and the threo isomers.…”

“…8.79[64], 7.95[41], 8.78[42]. In 80% methylcellosolve 7.95[41]7.36[67] ; h : Lit. 4.34[64], in 80% methylcellosolve 2.66[67], 2.40[68] ; i : Lit: 2.88[65], 3.71[42] ; j : Lit.…”

Addition of H-phosphonates to quinine-derived carbonyl compounds. An unexpected C9 phosphonate–phosphate rearrangement and tandem intramolecular piperidine elimination

“…Accordingly, heating of quinine or derivatives in acids provided either quino-/cinchotoxine ketones or their tautomeric enol esters, depending on the substrate structure and the reaction conditions [41–43]. The corresponding compounds were also suggested as the products of a base-catalyzed Hofmann elimination of quaternary quinuclidinium salts studied as chiral catalysts [44–45].…”

Ephedrine and Pseudoephedrine (C6–C1 Part Derived from l-Phenylalanine and Nitrogen Derived by Transamination)

“…From Table 20.1 [8] it is concluded that ephedrine (1) (the most populated conformer 1a) and its N-methyl derivative are weaker bases than ψ-ephedrine (2) (the most populated conformer 2a) and its N-methyl derivative, respectively. This also leads to the erythro configuration of ephedrine (1) and its N-methyl derivative and threo configuration of ψ-ephedrine (2) and its N-methyl derivative (Fig.…”