Consider the reducing (i.e., hydride-transfer) agents below: lithium aluminium hydride (LiAlH4); sodium borohydride (NaBH4); sodium cyanoborohydride [NaBH3(CN)]. Rank these species in the order of increasing nucleophilicity. Justify your answer by discussing the influence of the corresponding anion composition (atomic size; electronegativity; electron-withdrawing & electron-donating effects) on the energy level of the o orbital of the M-H bond. Based on your answer in Q3, suggest reagents and a strategy for the chemoselective reduction of the B-ketoester below to the corresponding B-hydroxyketone. Draw the intermediates - reaction mechanisms are not required. Hint: this synthetic sequence requires three steps. Na Li AlHz H BH3 H Na B(CN)H2 H O OH i COM R R