Rationally designed tetrahydropyrans (THPs) carrying one, two, or three aryl rings and other substituents were synthesized by the allylation of beta-hydroxy ketones followed by iodocyclization. It has been observed that compounds with one aryl ring on THP are moderate inhibitors of cyclooxygenase-1 (COX-1) (IC(50) = 0.3 microM) and cyclooxygenase-2 (IC(50) = 0.17 microM) with poor selectivity index (SI = 2-3) for COX-2. The presence of two aryl rings enhanced their inhibitory activities for COX-2 (IC(50) = 0.9-5.5 nM). Selectivity for COX-2 over COX-1 also increased (SI = 50-1900), while triaryl substituted THPs, along with high inhibition (IC(50) = 0.57-4.0 nM), also exhibited excellent selectivity for COX-2 over COX-1 (SI = 3200-44000). Similar to the experimental results of increased COX-2 inhibition and selectivity with the increase in the size of the molecule, their docking in the active sites of COX-1 and COX-2 also showed same trend. Seven compounds from the category of di- and triaryl substituted THPs exhibited average GI(50) over all the human tumor cell lines in the range 1.6-3.2 microM and showed in vitro therapeutic indices of 8-17.