A solution of (S)-2-benzyl-1-((3aS,8aR)-2,2-dimethyl-8,8a-dihydro-3 aH-indeno[1,2-d]oxazol-3-yl)-2,4-dihydroxy-butan-1-one (21g) (0.13 g, 0.34 mmol) in dry CH2Cl2 (5 mL) was added over 1 min to a stirred solution of Dess-Martin periodinate (0.16 g, 0.37 mmol) in dry CH2Cl2 (10 mL). After 30 min the homogeneous mixture was diluted with ether and poured into cold saturated NaHCO3 (10 mL) containing Na2S2O3 (2.2 g). Organic layers were washed with aqueous saturated NaHCO3, brine and dried (MgSO4). The solvents were evaporated below 20° C. to give the title compound (0.082 g, 64%). The residue [MS (ESI+): 380 (M++1)] was immediately used for the next step.
