Afterwards, the mixture was heated to 90 °C for 6 d. After allowing the mixture to cool down to RT, the phases were separated and the aqueous phase was extracted with EtOAc (3 x 100 mL). The combined organic layers were washed with brine, dried over Na 2 SO 4 , filtered and concentrated under reduced pressure. Pentane was added to the residue and the mixture was filtered. The solids were collected, cyclohexane was added and the suspension was sonicated for 30 min. The mixture was filtered again and the solid was dried in the high vacuum to afford diastereomer 8 (2.00 g, 4.64 mmol, 26%) as a white, amorphous solid. The filtrate of the second filtration was concentrated under reduced pressure, pentane was added and the suspension was sonicated for 10 min.