Design and synthesis of a combinatorial chemistry library of 7-acyl, 10-acyl, and 7,10-diacyl analogues of paclitaxel (taxol) using solid phase synthesis.

A series of 10-acyl and 7,10-diacyl paclitaxel analogues (7a-7e and 9a-9u) have been synthesized using a solid phase combinatorial chemistry approach, and a second series of 7-acyl-10-deacetylpaclitaxel analogues have been prepared by conventional chemistry. In the first series, 10-deacetylpaclitaxel (4) was linked through its 2'-hydroxyl group using 1% polystyrene-divinyl benzene resin functionalized with butyldiethylsilane linker (PS-DES) and then acylated at the C-10 hydroxyl group with various anhydrides and dialkyl dicarbonates in the presence of CeCl(3). The resin-bound C-10 acylated paclitaxel derivatives (6a-6e) were then treated with various carboxylic acids in the presence of 1,3-diisopropylcarbodiimide in toluene to provide polymer-supported 7,10-diacylpaclitaxels (8a-8u). These 7-acyl- and 7,10-diacylpaclitaxels (6a-6e and 8a-8u) were cleaved from the resin to give the 24 paclitaxel analogues 7a-7e and 9a-9u. Nine 7-acyl-10-deacetylpaclitaxel analogues were also prepared by conventional chemistry. Methodology to determine the tubulin-assembly activity of compounds prepared in small quantities by a combinatorial approach has been developed, and four analogues with improved tubulin-assembly activity as compared with paclitaxel were found, together with two analogues with improved cytotoxicity.