5]undecane 4 and its three congeners 5, 6, and 7 (α-methylspiroketals), and their reductive ring opening using aluminum hydride or silane - Lewis acid system have been investigated. Each spiroketal was synthesized through stereocontrolled acetalization with 42 – 96% diastereomeric excess (de). The diisobutylaluminum hydride reduction of α-methylspiroketals proceeded via the tight oxocarbenium ion pair complex