Total Synthesis\nof Tipranavir Based on Iridium-Catalyzed\nAsymmetric Allylic Substitution of Dihydropyranone

An\nefficient and highly enantioselective synthesis of\ntipranavir\nis realized based on an iridium-catalyzed asymmetric allylic substitution.\nHigh yield and diastereoselectivity (>20:1), as well as excellent\nenantioselectivity (99% <i>ee</i>), were obtained for the\nkey intermediate through direct asymmetric alkylation reaction of\ndihydropyranone with allylic <i>tert</i>-butyl carbonate.\nAnti-AIDS drug of tipranavir was finally accomplished in 8 steps and\n6 pots starting from commercially available 1-phenyl-3-hexanone in\n20.7% overall yield with 99% <i>ee</i> and >20:1 <i>dr</i>.