The formal synthesis of pinnaic acid (1) is summarized
in Scheme 2. Selective silylation of the diol 12 with
TBDPSCl, Et3N, and catalytic DMAP afforded 13 in 87%
yield. Jones oxidation of 13 furnished carboxylic acid 14,
which was subjected to a Curtius rearrangement with
diphenyl phosphoryl azide (DPPA)17 and t-BuOH to afford
10 in 51% yield for the two steps