Replacement of the 3,4-dialkoxyphenyl substructure common to a number of PD
E4 inhibitors with a 2-alkyl-7-methoxybenzofuran unit is described. This su
bstitution can result in either enhancement or substantial reductions in PD
E4 inhibitory activity depending on the system to which it is applied. An i
n vitro SAR study of a potent series of 4-(2-heteroaryl-ethyl)-benzofurans
26 is also presented. (C) 1999 Elsevier Science Ltd. All rights reserved.