“…Purification by flash chromatography (hexanes/EtOAc, 0:100) provided the known compound 28 (4.2 g, 70%). Characterization data correlate with the previously reported data: R f = 0.28 (hexanes/EtOAc, 0:100); [α] D 25 +79 ( c = 0.9, MeOH); C 4 H 6 O 3 ; MW = 102.0886 g/mol; 1 H NMR (500 MHz, CDCl 3 ) δ 4.70–4.66 (m, 1H), 4.42 (dd, J = 10.3, 4.5 Hz, 1H), 4.30 (appd, J = 10.3 Hz, 1H), 2.86 (d, J = 3.8 Hz, 1H), 2.75 (dd, J = 17.9, 6.1 Hz, 1H), 2.52 (dd, J = 18.0, 1.0 Hz, 1H) ppm.…”