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1 H− 15 N HMBC spectra of norditerpenoid alkaloids and their synthetic azabicyclic analogues were obtained to investigate the impacts of the through-space effect of steric compression, protonation, and formation of intramolecular hydrogen bonding on the 15 N NMR spectroscopy of these natural products and their piperidine-containing analogues. A rare 15 N NMR effect of steric compression is demonstrated in half-cage A/E-rings of norditerpenoid alkaloid free bases and their synthetic azabicyclic analogues, in which the distribution of the lone pair of electrons of the tertiary amine N-atom is sterically restricted by bridged cycloalkanes, e.g., cyclopentane, cyclohexane, and cycloheptane rings. This results in significant changes in the 15 N chemical shift, typically by at least ∼10 ppm. The lone pair of electrons of the N-atom in the piperidine ring are sterically compressed whether the bridged cyclohexane ring adopts a chair or boat conformation. The 15 N chemical shifts of 1α-OMe norditerpenoid alkaloid free bases significantly increase (Δδ N ≥ 15.6 ppm) on alkaloid protonation and thence the formation of an intramolecular hydrogen bond between N + -H and 1α-OMe. The intramolecular hydrogen bonds between the N-atom and 1α-OH of 1α-OH norditerpenoid alkaloid free bases, karacoline, condelphine, and neoline stabilize their A-rings, adopting an unusual twisted-boat conformation, and they also significantly increase δ N of the tertiary amine N-atom.

Solutions of pure cannabinoids, nine samples of herbal and two of resin cannabis (one freshly prepared) were stored in varying conditions for up to 2 years. Exposure to light (not direct sunlight) was shown to be the greatest single factos in loss of cannabinoids especially in solutions, which should therefore be protected from light during analytical and phytochemical operations. Previous claims that solutions in ethanol were stable have not been substantiated. The effect of temperature, up to 20 degrees, was insignificant but air oxidation did lead to significant losses. These could be reduced if care was taken to minimize damage to the glands which act as "well filled, well closed containers". Loss of tetrahydrocannabinol after exposure to light does not lead to an increase in cannabinol, but air oxidation in the dark does. It is concluded that carefully prepared herbal or resin cannabis or extracts are reasonably stable for 1 to 2 years if stored in the dark at room temperature.