Saturated amine oxides: Part 5. Hydroacridines: Part 24.¹³C NMR chemical shifts of N‐epimeric saturated six‐membered azaheterocyclic amine oxides

Abstract

The 13 C NMR spectra of 22 piperidine-, tropine-and tetradecahydroacridine-derived saturated amine oxides were measured. The chemical shifts were assigned on the basis of APT and 2D-INADEQUATE spectra, and are briefly discussed.

Saturated amine oxides: Part 8†. Hydroacridines: Part 27‡. Effects of N‐oxidation and of N‐quaternization on the 15N NMR chemical shifts of N‐methylpiperidine‐derived mono‐, bi‐, and tricycloaliphatic tertiary amines

“…3,4 With the aim to expand this knowledge, we report and discuss here the 15 N chemical shifts data of 13 N-methylpiperidine-derived mono-, bi-, and tricycloaliphatic tertiary amines and their N-epimeric pairs of N-oxides, which we have already studied by 13 C and 17 O NMR spectroscopy. 5,6 In view of the total lack of data concerning correlations between structure and 15 N (or 14 N) NMR chemical shifts of aliphatic quaternary ammonium salts (so far we became aware only of the chemical shifts of the tetramethyl-, 7,8 tetraethyl- 7,8 and tetrapropylammonium ions 7 in several solvents, mainly given with regard to their use as shift reference compounds), we also report and discuss the 15 N NMR chemical shifts of the methiodides of the abovementioned amines.…”

Synthesis of (±)-Serralongamine A and the Revised Structure of Huperzine N

“…The configuration of the new stereogenic center at the nitrogen atom in huperzine N was corroborated as R , on the basis of 1 H and 13 C chemical shift NMR analysis of 1 and its N -epimer 12 . Thus, a clear upfield shift for C(3), C­(4a), and C(8) was observed, due to the 1,3-cis relationship between the N→O bond and the axial C–H bond of these carbon atoms (Figure ), compared with either the free amine base nucleus (e.g., in 2 ) or the N -epimeric N -oxide with the oxygen atom in an equatorial disposition (i.e., 12 ) . The NMR data of synthetic huperzine N matched those described for the natural product, thus establishing its configuration as 1 R ,4a S ,5 S ,7 R ,8a S .…”

Decahydroquinoline Ring 13C NMR Spectroscopic Patterns for the Stereochemical Elucidation of Phlegmarine-Type Lycopodium Alkaloids: Synthesis of (−)-Serralongamine A and Structural Reassignment and Synthesis of (−)-Huperzine K and (−)-Huperzine M (Lycoposerramine Y)

“…After carefully examining these data, we realized it was possible to deduce basic rules to determine the stereochemistry of a defined compound. When applying the information given in Table to elucidate the stereostructure of new phlegmarine-type alkaloids, additional parameters (electronic and steric effects) should of course be considered, depending on the nitrogen atom substituent . Also pertinent is that secondary and tertiary amines easily undergo a partial or total protonation in the processes of isolation, synthesis, or NMR spectroscopic analysis in CDCl 3 , which can lead to variations in the recorded NMR spectra of up to almost 2.5 ppm .…”