Colchicine chemical structure

Chart 1 Chemical structures of colchicine (1), combretastatin A-4 (2), podophyllotoxin (3), vinblastine (4) and vincristine (5)... 

Chart 5 Chemical structures of allocolchicine (6), 2-mcthoxy-5-(2, 3, 4 -tri methoxy phenyl )-tropone (MTC) (7) and 2-methoxyestradiol (8), analyzed together with colchicine and CA4 through the MultiSEAL alignment procedure... 

Fig. 1 Chemical structures of Colchicine (1), Vinblastine (2), Vincristine (2a) and Taxol...

The family of colchicines-site binders includes compounds of diverse structure unified by interference with the colchicine binding epitope. The respective compounds can be clustered according to their chemical structure mainly into I) colchicines and compounds with colchicine like substructures, II) combretastatins and phenstatins, III) compounds having an indole core structure, IV) quinolones, V) sulphonamidcs and VI) naturally occurring as well as synthetic compounds. 

Fig. 7 Chemical structures of indanocine, RPRl 12378 and RPR 115782, compounds affecting the colchicine binding site...

Most alkaloids have basic properties coimected with a heterocyclic tertiary nitrogen. Notable exceptions are colchicine, caffeine, and paclitaxel. Most alkaloids are biosynthetically derived from amino acids such as phenylalanine, tyrosine, tryptophan, ornithine, and lysine. Alkaloids represent a wide variety of chemical structures. About 20000 alkaloids are known, most being isolated from plants. But alkaloids have also been found in microorganisms, marine organisms such as algae, dinoflagellates, and puffer fish, and terrestrial animals such as insects, salamanders, and toads. 

In the post-World War II years, synthesis attained a different level of sophistication partly as a result of the confluence of five stimuli (1) the formulation of detailed electronic mechanisms for the fundamental organic reactions, (2) the introduction of conformational analysis of organic structures and transition states based on stereochemical principles, (3) the development of spectroscopic and other physical methods for structural analysis, (4) the use of chromatographic methods of analysis and separation, and (5) the discovery and application of new selective chemical reagents. As a result, the period 1945 to 1960 encompassed the synthesis of such complex molecules as vitamin A (O. Isler, 1949), cortisone (R. Woodward, R. Robinson, 1951), strychnine (R. Woodward, 1954), cedrol (G. Stork, 1955), morphine (M. Gates, 1956), reserpine (R. Woodward, 1956), penicillin V (J. Sheehan, 1957), colchicine (A. Eschenmoser, 1959), and chlorophyll (R. Woodward, 1960) (page 5). ... 

In addition to effects on biochemical reactions, the inhibitors may influence the permeability of the various cellular membranes and through physical and chemical effects may alter the structure of other subcellular structures such as proteins, nucleic acid, and spindle fibers. Unfortunately, few definite examples can be listed. The action of colchicine and podophyllin in interfering with cell division is well known. The effect of various lactones (coumarin, parasorbic acid, and protoanemonin) on mitotic activity was discussed above. Disturbances to cytoplasmic and vacuolar structure, and the morphology of mitochondria imposed by protoanemonin, were also mentioned. Interference with protein configuration and loss of biological activity was attributed to incorporation of azetidine-2-carboxylic acid into mung bean protein in place of proline. 

Combretastatins are a class of compounds originally derived from the African Willow tree (Combretum caffrum) and are powerful reversible inhibitors of tubulin polymerization. This class of molecules has been shown to bind to the colchicine binding site of tubulin, by the same mode of action as mentioned above (Sect. 1.2). Combretastatins consist of a ris-slilbcnc core structure. To date, there have been several compounds that have shown promise as potential anticancer drugs. However, development of these compounds as anticancer agents is limited by issues of chemical stability, bioavailibilty, toxicity, and solubility. 

The cause of the cell cycle specificity of the bisindole alkaloids may be associated with the ability of these compounds to interact with the protein tubulin and thereby inhibit the polymerization (and depolymerization) of microtubules (16,17). In this respect the cellular pharmacology of vinca alkaloids is similar to that of other cytotoxic natural products such as colchicine or podophyllotoxin. On closer inspection, however, Wilson determined that the specific binding site on tubulin occupied by vinblastine or vincristine is chemically distinct from the site occupied by the other natural products (18). Subsequent experiments have determined that the maytansinoids, a class of ansa-macrocycles structurally distinct from the bisindoles, may bind to tubulin at an adjacent (or overlapping) site (19). A partial correlation of the antimitotic activity of these compounds with their tubulin binding properties has been made, but discrepancies in cellular uptake probably preclude any quantitative relationship of these effects (20). 

Structure and Reactions of Colchicinb With the publication of Volume II of this series, studies on the structure of colchicine had progressed to the stage where only two formulas, XLI and XLII, seemed compatible Avith the accumulated chemical evidence. The pioneering efforts of Windaus left no doubt that the... 

---