A straightforward trifluoromethylation at the C6 position of morphinane alkaloids, their modification and evaluation of inhibition of the SARS-CoV-2 main protease

A catalytic trifluoromethylation of stereoisomeric 6-ketomorphinans using Ruppert–Prakash reagent and tetrabutylammonium fluoride (TBAF) was studied. 14β-Hydroxycodeinone, 4-O-methylsinomenine and 1-iodo-4-O-methylsinomenine provided good to excellent yields of the corresponding 6-trifluoromethylated compounds. The new morphinan derivative (6-deoxo-1-iodo-6α-(trifluoromethyl)-4-O-methylsinomenin-6β-ol) was involved in some catalytic transformations for introduction of additional substituent on C-1 position of the morphinan core. The palladium-catalyzed carbonylation–cross coupling reaction of 1-iodo-derivative with phenylacetylene in the presence of PdCl₂-(1-Ad)₂PBn catalytic system and Mo(CO)₆ as a source of carbon monoxide in MeCN proceeds with high selectivity with the formation of alkynyl ketone as the main product. The cyclocondensation with acetamidine hydrochloride afforded the arylpyrimidine – 6α-(trifluoromethyl)-4-O-methylsinomenin-6β-ol hybrid compound. The action of the dehydration system (SOCl₂-Py-DMAP) on 6-deoxo-6α-(trifluoromethyl)-4-O-methylsinomenin-6β-ol have led to the formation оf 8β‑chloro-6,7-didehydro-6-(trifluoromethyl)morphinan which showed inhibition the main viral protease (3CLpro) of SARS-CoV-2 at IC₅₀ value of 25 μM.