... The combined organic layers were washed twice with 50 mL of water, dried over magnesium sulfate, and concentrated under reduced pressure. ... (6) For reviews of butenolide chemistry: (a) Rao, YS Chem. Rev. 1964,64,353. (b) Rao, YS Ibid. ... Page 2. Notes J. Org. Chem., Vol. ...