4-Aza-2,3-dehydro-4-deoxypodophyllotoxin analogues 3a-n were synthesized through quinolines 2a-n. Comparison of their cytotoxicity against P-388 leukemia cells revealed that the steric effects of the ring B substituents on the activity are greater than the electronic effects, while the presence of a methoxy group on the ring E is not essential to exhibit potent cytotoxicity. Analogues 3a and 3b proved to be more than twice as cytotoxic as natural podophyllotoxin (1). (C) 2000 Elsevier Science Ltd. All rights reserved.
Heterocalixarenes. Part 4. Synthesis of oxocalix[1]heterocycle[2]arenes: a unique H-bonding network in calix[1]benzimidazol-2-one[2]arene· 1/2 H2O †
and quinazoline-2,4(1H,3H)-dione provide respective oxocalix[1]heterocycle[2]arenes 5–9. The X-ray crystal structure (solid) and 1H NMR spectral (solution) studies show them to have by and large inwardly flattened partial cone conformations which vary in torsion angles between the rings. The calix[1]benzimidazol-2-one[2]arene·½ H2O complex shows a unique array of H-bonds in which three of the four CH