71 by abiding both the Felkin-Anh rule and the Zimmerman-Traxler model (Scheme 24). However, the Felkin-type transition states leading to 71 suffer from severe 1,3-syn-pentane (cf. 73) or gauche (cf. 74) interactions. In contrast, the anti-Felkin transition state 75 minimizes both 1,3-syn-pentane and gauche interactions, leading to 72 as the preferred diastereomer