Isolation and characterization of synthesis intermediates and side products in hexahydrocannabiphorol

After the Swiss ban of hexahydrocannabinol (HHC) in March 2023, other semisynthetic dibenzopyran cannabinoids emerged on the Swiss gray market. Hexahydrocannabiphorol (HHCP) was the most prominent of them due to its potent cannabimimetic effects, as anecdotal reports from recreational users suggest. In October 2023, a class wide ban of dibenzopyran cannabinoids was introduced in Switzerland to prevent new similar substances from entering the drug market. Various vendors in online shops claim that HHCP is made from CBD, even though they possess different alkyl chain lengths. An HHCP sample was analyzed by gas chromatography coupled to mass spectrometry (GC-MS), showing that a mixture of molecules with the same or a similar molecular mass as HHCP was present. Six different substances could be isolated from this sample using column chromatography. Four phenols ((9R)-HHCP, iso-HHCP, cis-HHCP, and abn-HHCP) and two ketones (possible intermediates to (9R)-HHCP and abn-HHCP) were identified by various nuclear magnetic resonance spectroscopy (NMR) techniques. (9S)-HHCP was obtained in an impure fraction. In addition, a fraction was obtained that showed characteristic molecular and fragment ions consistent with bisalkylated products from the synthesis of similar compounds. The presence of abnormal cannabinoids (abn-HHCP) and bisalkylated cannabinoids is a confirmation that this sample was produced purely synthetically as initially suspected, as these compounds have not been reported in Cannabis. Chiral derivatization of the phenols with Mosher acid chlorides showed that only iso-HHCP was present as a scalemic mixture, indicating a good stereocontrol of this synthetic procedure.

Eco-friendly synthesis of fused pyrano[2,3-b]pyrans via ammonium acetate-mediated formal oxa-[3 + 3]cycloaddition of 4H-chromene-3-carbaldehydes and cyclic 1,3-dicarbonyl compounds

Various substituted polycyclic pyrano[2,3-b]pyrans were synthesized via the condensation of 4H-chromene-3-carbaldehydes and their areno-condensed analogues with hetero- and carbocyclic 1,3-dicarbonyl compounds in acetic acid. Ammonium acetate was used as a green catalyst for the reaction. The process also involves the subsequent Knoevenagel condensation and 6π-electrocyclization of the 1-oxatriene intermediates formed. Fused pyridines were isolated as the products of the conjugated addition of ammonia to 1-oxatriene intermediates while using carbocyclic 1,3-dicarbonyl compounds and increasing the reaction time, indicating the reversibility of the electrocyclization stage. The calculated values of the Gibbs free energies and reaction rate constants for the 1-oxatriene - 2H-pyran equilibrium also testified to the irreversibility of pyrano[2,3-b]pyran formation in the case of using of heterocyclic 1,3-dicarbonyl compounds.