Carbon‐13 Magnetic Resonance Spectroscopy. A Study Of Colchicine And Related Compounds

Abstract

The carbon‐13 NMR signals of twelve cochicinic derivatives, have been assigned and some 1H‐13C coupling constants have been measured. The substituent effects, the colchicine‐isocolchicine isomerism, the prototropy of colchiceine and trimethylcolchicinic acid and the acylotropy of colchiceine acetate are discussed. There is a slight predominance of the isocolchicinic tautomer, both in the case of the prototropy and the acylotropy.

Colchiceine Complexes with Lithium, Sodium and Potassium Salts − Spectroscopic Studies

“…Colchiceine exists in the form of two tautomers, which follows from intramolecular proton transfer on the tropolone moiety (between two oxygens at C-9 and C-10). [27] The 1 H NMR spectra of colchiceine complexes 3-8 do not show significant changes in the values of chemical shifts of respective hydrogen atoms, as has been also observed earlier for other biologically active compounds like monensin, oligomycin and complexes of colchicine. [25,[28][29][30][31][32] The slightest changes of proton chemical shifts have been observed for the amide group.…”

NMR and DFT investigations of structure of colchicine in various solvents including density functional theory calculations

“…Additional NMR studies were conducted by Mweksuriyen et al . 7 to complete the 13 C NMR assignment of the carbons in light of discrepancies in the earlier reports 8 , 9 despite a large literature regarding the structural aspects of colchicine 10 – 15 . The discrepancies associated with earlier studies can be ascribed due to the overlapping signals in the NMR spectrum as well as the lack of advanced pulse programs for detailed NMR analysis that are now available.…”

“…The discrepancies associated with earlier studies can be ascribed due to the overlapping signals in the NMR spectrum as well as the lack of advanced pulse programs for detailed NMR analysis that are now available. For example the chemical shifts have been reported as being 150 ppm, 153.8 ppm and 151.1 ppm for C1 and 151.4 ppm and 153.5 ppm for C3 8 , 9 . Recently, Virgili et al .…”

Synthesis and Antiproliferative Screening Of Novel Analogs of Regioselectively Demethylated Colchicine and Thiocolchicine

“…It is, next to lumicolchicine (Figure 1), the main product of colchicine degradation and can naturally occur in plant extracts together with colchicine [31]. Elguero et al [32] have established that colchiceine (as well as its C10-acylated analog) can occur in two tautomeric forms, from which the isoform is slightly more dominant. This equilibrium between colchiceine and isocolchiceine ( Figure 1) exists also in the solid state, which has been confirmed by X-ray diffraction studies [33].…”