Synthesis of the C-13 Side Chain Precursors of the 9-Dihydrotaxane Analogue ABT-271

<i>N</i>-Boc-l-Leucinol was converted to two C-13 side chain precursors of the 9-dihydrotaxane analogue ABT-271. The <i>trans</i>-oxazolidine acid <b>4</b> and the c<i>is</i>-Boc-lactam <b>2b</b> were prepared in 44% and 40% overall yield, respectively, and with excellent (>98%) stereochemical purity.