Synthesis of cyclic oligomers of pivalolactone has been performed by a cyclooligomerization strategy promoted by a simple catalytic system: potassium alkoxides. The thermodynamic control of macrocyclic oligomerization and yields of macrolides of pivalolactone depend on the reaction conditions, specifically temperature and concentration. In dilute solution, the yield of macrocyclic oligomers is around 75%, in which the trimer and tetramer are the major products. The 16-membered tetrolide has been isolated in crystalline form and its structure has been proven by X-ray crystal structure analysis. The mechanism of the cyclooigomerization is discussed. The strategy of cyclooligomerization with an anionic catalyst offers a unique, simple synthesis of pivalolactone cyclic oligomers, which are potential ligands for metal complexation.
An Unexpected Formation of a 14-Membered Cyclodepsipeptide
作者:Boyan Iliev、Anthony Linden、Heinz Heimgartner
DOI:10.1002/hlca.200390262
日期:2003.9
The treatment of diluted solutions of the hydroxy diamides 6a and 6b in toluene with HCl gas at 100° gave the dimeric, 14-memberedcyclodepsipeptide 10 in up to 72% yield (Scheme 3). The same product was formed from the linear dimer of 6b, the depsipeptide 11, under the same conditions (cf. Scheme 4). All attempts to prepare the cyclic seven-membered monomer 9, starting with different precursors and