Colchicine synthesis

The synthesis of five-, six-, and seven-membered cyclic esters or timides uses intramolecular condensations under the same reaction condifions as described for intermolecular reactions. Yields are generally excellent. An example from the colchicine synthesis of E.E. van Ta-melen (1961) is given below. The synthesis of macrocyclic lactones (macrolides) and lactams (n > 8), however, which are of considerable biochemical and pharmacological interest, poses additional problems because of competing intermolecular polymerization reactions (see p. 246ff.). Inconveniently high dilution, which would be necessary to circumvent this side-... 

Coformycin, 2 -deoxy—see Pentostatin Colchicine synthesis, 1, 472 isothiazoles in, 6, 174 Collins reagent as oxidizing agent, 2, 170 Colour... 

Michael addition with methyl propiolate led in this case directly to the tricyclic a-pyrone 84, which is a central intermediate in Eschenmoser s colchicine synthesis [35]. 

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