MACROCYCLES DERIVED FROM CINCHONA ALKALOIDS - A THERMODYNAMIC VS KINETIC-STUDY

Cyclization of the quiuine-derived monomer (2a): HO-Cq-OMe, under ther modynamic control, gives mainly cyclic trimer Cq(3) (7a), whereas kine tic cyclization of the similar monomer HO-Cq-OH (8) gives a mixture of cyclic products. This difference in product distribution is attribute d to predisposition of the monomer unit, which means the building bloc k adopts a more stable conformation in cyclic trimer than it can in cy clic tetramer. The reversibility of the thermodynamic reaction was dem onstrated using electrospray mass spectrometry to monitor the catalyze d mixing of the two cyclic trimers Cq(3) (7a) and Cc(3) (7b), which re sults in the statistically expected 1:3:3:1 ratio of all possible cycl ic trimers Cc(3):Cc(2)Cq:CeCq(2):Cq(3).